Continuous piezoionicity-driven electromechanical coupling in mechanically robust conductive eutectogels

Domain: physics
Published: 2025-12-10
Editorial outcome: major_revision

Abstract
Somatosensory network-sensitive ionic currents, responding to tactile bio-signals, serve as behavioral modulation for electromechanical transduction. Building on these biological principles, here we show mechanically robust, conductive piezoionic eutectogels with hierarchical structure enabling continuous pressure-driven ion migration, effectively transducing pressure into ionic streaming. This electromechanical coupling originates from pressure-sensitive differences in cationic and anionic mobility, producing net streaming potentials. The piezoionic eutectogels, reaching sensitive, continuous response of ~200 s to innocuous force, governed by the engagement of both pronounced mechanosensitivity under applied pressure and ion inactivation kinetics upon releasing. The piezoionic mechanism is attributed to hierarchically orientated ion-steaming and charge compensation mechanism, dynamically regulating ion transmission. This ion streaming-driven piezovoltage depends on pressure magnitude, pressure duration and mechanical environments, achieving continuous peak piezovoltage up to 40 mV at 3.0 MPa. This work provides synergistic molecular–structural design towards piezoionic dynamics and mechanical performances, offering insights into next-generation piezoionics.

Introduction
In living organisms, the synergistic interactions between mechanosensory systems and mechanical stimuli relying on ion-selective protein channels can convert and transmit pressure signals into electrophysiological signals with excitatory and inhibitory features, such as soft cutaneous mechanoreceptors1–3. Intrinsically, the rich set of mechanoreceptors, mechanosensitive ion channels, found in human skin accurately transduce tactile sensations, i.e., mechanical stimulus, into electrophysiological signals that propagate to the central nervous system via mechanotransduction machinery to achieve biological perceptions and interactive responses (Fig. 1A)4–6. Inspired by the sensory behavior of soft mechanoreceptors residing within skin, iontronics is rapidly expanding owing to promising applications in biocompatible sensors, e-skin and biomedicine, and energy-conversion, harvesting and storage7,8. As suggested by the emergence of piezo-materials, capabilities for perceiving and responding to external stress stimuli have attracted considerable attention owing to their ability to generate iontronic/electrical signals or ionic/electronic currents. Piezoelectric materials can convert mechanical forces into electrical signals, whereas piezoionic materials tend to be based on the movement of ions rather than electrons in response to pressure gradients. Consequently, piezoionic materials, like electric organs, are regarded as a very good match for biosensing and biointerfaces.

Piezoionics, as fast-emerging iontronics, relies on pressure-induced electrogenesis via ion currents to integrate electromechanical coupling, providing an alternative for taking advantage of ubiquitous mechanical energy in behaviors and movements9. When subjected to mechanical force, piezoionic matrices produce ionic currents through one of two phenomena: either the concerted flow of ions of a single charge, or the selective transport of one ionic species over its counterions due to differential mobility within the polymer network, thereby establishing net charge imbalance10,11. Particularly, piezoionic hydrogel functions through converting the applied force into ion streams, enabling an important role in flexible bioelectronics and biosensors, such as a silent-speech recognition system transforming laryngeal mechanical vibrations into silent speech, and a neuromodulation interface eliciting hindlimb movement via tactile-induced current pulses, owing to exceptional biocompatibility, mechanical flexibility (Fig. 1B)11,12. Despite their promising potential, soft piezoionics faces significant challenges, including limited mechanosensitivity and short-term pressure-induced piezovoltages under prolonged or strong pressure simulation. This phenomenon stems from an inherent compromise between mechanical robustness and piezoionic performance: soft materials readily establish a pronounced pressure gradient under stress, whereas stiff materials resist forming a significant pressure gradient.

Mechanically weak piezoionics fail to render the contribution to continuous ionic current production in response to mechanical forces, along with mechanical failure under persistent loading. Whereas the mechanosensitivity and ionic transmission may be sluggish in mechanically strong piezoionic gels owing to the weak pressure gradient caused by stress concentration. Therefore, a persistent challenge lies in balancing the structural requirements and molecular designs in soft piezoionics for integrating prominent mechanosensitivity, ionic transmission, and mechanical robustness to produce continuous, stabilized pressure-driven ion flux. Advances in strategies for establishing or designing the synergistic methodology from molecular and structural engineering perspectives have contributed to an explosion of personalized polymer gel13–15. Despite the supportive contributions of mechanical performances in realistic application scenarios, its synergism with functionality remains largely unknown owing to the incompatibility or mismatch between accessible performances and functionalities. To this end, we envisioned that the synergistic designs in molecular and structural engineering are an ideal orthogonal manufacturing technology to make mechanosensitive, mechanically strong piezoionic gels.

Herein, we have succeeded in developing a mechanically robust piezoionic eutectogels (PIEgels) for continuous piezoionicity-driven ionic currents via mechanically activated cation channels, employing Na+ as pressure-driven ion flux to generate piezovoltage. Structurally, PIEgels present hierarchically interpenetrating networks engineered via mechanical training, accelerating ionic conduction via directional transport of ion steaming and improving ionic transmission via lower spatial barriers in hierarchical networks. Molecularly, conductive polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) is regarded as a charge-compensated receptor of NaCl to improve mechanosensitivity, contributing to diffusion and inactivation kinetics of Na+ transmission. When applying pressure, the Cl−-to-hole binding in PEDOT skeletons substantially promotes the diffusion kinetics of Na+, resulting in considerable mechanosensitivity; whereas the Na+-to-(−SO3−) binding in PSS chains facilitates inactivation kinetics, leading to the continuous piezovoltage when removing the pressure. Benefiting from efficient synergistic effect in molecular and structural engineering, i.e., hierarchical structure and charge compensation mechanism, the resulting PIEgels combine enhanced mechanical robustness and piezoionic effects (peak piezovoltage of 40 mV at 3.0 MPa), and serve as continuous pressure-driven ion migration to generate piezoionic output of ~200 s.

Results
Molecular and structural design of mechanically robust conductive PIEgels
A key surprising feature of the transmembrane transport of ions in cutaneous mechanoreceptors is the conversion of mechanical stimulus acting on the skin into electrophysiological signals propagating to central nervous system, providing inspiration for electromechanical coupling in soft piezoionics (Fig. 1A, B). Following this transduction mechanism, we fabricated a mechanically robust, conductive PIEgels that produces continuous electric power via ion streaming relied on mechanical force. We utilized conductive polymer PEDOT:PSS-supported conductivity to construct mixed ionic–electronic conductors, i.e., PIEgels, which may provide an accessible pathway for facilitating pressure-driven ion migrations. The mechanically robust PIEgels are fabricated via mechanical training, which incorporates deep eutectic solvent (DES) as substituted solvent within semicrystalline PVA/PEDOT:PSS hydrogel to conduct mechanical training for building hierarchical structure.

Particularly, the PVA were dissolved in PEDOT:PSS aqueous solution to fabricate PVA/PEDOT:PSS precursor. We firstly used the freezing-thawing and subsequent salting-out treatment to synthesize isotropic single-network PVA/PEDOT:PSS hydrogel (SNH) cross-linked via hydrogen bonding. Then, we used DES, composed of glycerol (Gly) and choline chloride (ChCl) in a molar ratio of 2:1, to carry out solvent displacement of PVA/PEDOT:PSS hydrogel for transforming into a single-network eutectogel (SNE). Because of abundant and strong hydrogen bonding nanocrystalline domains, PVA/PEDOT:PSS eutectogel embodies mechanical hysteresis, and allows mechanical training to be completed with only single pre-stretching. The SNE adopts reorientation of PVA nanofibrils to form a hierarchical network driven by external uniaxial force during the mechanical training. To further lock the aligned nanofibrils in the perpendicular to the stretching direction, we introduced a chemically cross-linked second network in SNE, i.e., P(AAm-co-AAc), into mechanically trained eutectogel to synthesize a double-network eutectogels (DNE) using UV-initiated radical polymerization, which features hierarchically interpenetrating network (Fig. 1C). More importantly, the pressure-driven ion migrations in hierarchically interpenetrated PIEgels, no longer like piezoionic hydrogels, but are orientated the transmission pathway. That is, the ion currents migrate between hierarchical nanofibrils and does not spread out in space, thus addressing the trade-off between mechanical robustness and piezoionic effect (Fig. 1D).

To our surprise, by synergistically deploying solvent substitution treatment and subsequent mechanical training process, weak and soft PVA hydrogel with 20 wt% PEDOT:PSS, treated with sodium chloride (20PP–Na), with Young’s modulus of 0.64±0.04 MPa, fracture strength of 1.49±0.04 MPa, and work of rupture of 3.45±0.33 MJ m–3, is facilely transformed into SNE (20PP–SNE) via solvent substitution, with Young’s modulus of 15.61±0.62 MPa, fracture strength of 8.16±0.99 MPa and work of rupture of 29.56±1.00 MJ m–3, and is significantly reinforced into strong DNE (20PP–DNE) via mechanical training and covalent network, with Young’s modulus of 21.72±1.50 MPa, fracture strength of 23.53±0.78 MPa and work of rupture of 42.39±1.60 MJ m–3 (Fig. 1E and Supplementary Fig. 1). From the perspective of conductivity, we demonstrated that PIEgels leverage the ion-electron coupling effect between PEDOT:PSS and ions (i.e., Na+ and Cl−) to promote ion exchange and facilitate electrical conductivity, resulting in exceptional electrical conductivity of 0.164±0.0276 S cm–1 in comparison with the eutectogels without NaCl or without PEDOT:PSS. The primary assignment of PEDOT:PSS is not to provide electronic conductivity, but to facilitate ionic conductivity (Fig. 1F and Supplementary Fig. 2)16,17.

By integrating conductive polymer and progressive manufacturing procedures, the resultant PIEgels exhibit satisfactory mechanical properties and conductivity, contributing to the orientated, continuous pressure-driven ion steaming for producing piezovoltage output, with peak piezovoltage of averaged 40 mV at 3.0 MPa. (Fig. 1G and Supplementary Fig. 3). In contrast to previously reported piezoionic hydrogels, the resultant PIEgels achieve a harmonious integration of mechanical robustness and piezoionic performance, thereby resolving the inherent conflict between these two properties (Fig. 1H, I and Supplementary Table 1). The significant mechanical properties coexist with instantaneous piezoionicities within piezoionic gels in hopes of achieving neuromodulation devices, biohybrid machines, and energy harvesters10,18,19.

Mechanical properties and strengthening mechanism of PIEgels
We first investigated the in-depth mechanistic insight of considerably reinforced mechanical performance into the progressive manufacturing procedures, i.e., salting out, solvent substituting, mechanical training and chemical network, with the goal of network structure–mechanical performance correlation using wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS) measurements and scanning electron microscopy (SEM) images. We evaluated the mechanical properties of various gels with different contents of PEDOT:PSS treated by salting out, i.e., 0%, 10% and 20%, with the nomenclature 0PP, 10PP and 20PP, respectively.

Notably, pure freeze-thawed PVA/PEDOT:PSS hydrogel fails to carry out tensile experiment attributed to poor mechanical performances. Obviously, 20PP–Na exhibits a 2.4-fold-higher modulus, 1.4-fold-higher strength and 2.0-fold-higher work of fracture in comparison to 0PP–Na, which indicates that the moduli, strengths and work of fracture increased with the extension of PEDOT:PSS (Fig. 2A, B). This is attributed to chemical bonding in the −SO3− group of PEDOT:PSS and the –OH of PVA, which is consistent with network structure (Supplementary Fig. 4) and FTIR analysis (Supplementary Note 1)20. Structure-wise, the strong diffraction peak at 2θ=19.5° in 1D WAXS profiles, corresponding to the typical reflection plane of (101) in semicrystalline PVA, indicates the higher PVA crystallization (Supplementary Fig. 6)21,22. Compared to the porous structure of 20PP, the SEM image indicates that the salting-out 20PP–Na demonstrates the anisotropic structure without only pore walls. This structural transformation originates from the strongly induced aggregation and crystallization of PVA during the salting-out process, mediated by phase separation (Fig. 2C, Supplementary Figs. 7 and 8)23.

Similar trend is observed in the SNE without mechanical training, that is, the moduli, strengths and work of fracture of SNE gradually increased with the extension of PEDOT:PSS. Particularly, 20PP–SNE merely demonstrates a 1.2-fold-higher modulus, 1.0-fold-higher strength and 1.2-fold-higher work of fracture in comparison to 0PP–SNE (Fig. 2D, E). Diffraction peaks at 22.5°, belonged to (200) plane of PVA, appear in WAXS intensity plots after the DES substitution, indicating the enhanced crystallinity, and resulting in the formation of nanocrystalline domains (Supplementary Figs. 6 and 8). While potent, this processing fails to exhibit strong sensitivity to the PEDOT:PSS contents in comparison to salting-out hydrogels, which result from that DES primarily interacts with PVA to form nanocrystals, rather than PEDOT:PSS during solvent displacement24,25. That is, DES substitution-induced the nanocrystalline domains become the dominant dissipative energy, resulting in the reinforced mechanical properties in comparison to salting-out hydrogels.

Subsequently, mechanical training builds a hierarchical structure, which is verified by hierarchical alignment of nanofibrous observed in SEM images and SAXS. (Fig. 2F and Supplementary Fig. 7). Additionally, mechanical training substantially reinforces mechanical performances of SNE, especially in terms of fracture strength, whereas results in the decrease in stretchability (Supplementary Fig. 9). To advance this disadvantage, we further introduced a chemically cross-linked second network via immersed in DES precursor containing monomer, i.e., P(AAm-co-AAc), to form DNE for enhancing mechanical properties. In particular, 20PP–DNE exhibits a 1.3-fold-higher modulus, 1.8-fold-higher strength and 4.4-fold-higher work of fracture in comparison to 0PP–DNE (Fig. 3G, H). Meanwhile, WAXS demonstrates that compared to SNE, DNE presents enhanced crystallinity, indicating that DES precursor solution further induces the formation of nanocrystalline domains. This immersion process presumably facilitated the enhanced bonding between PVA and PSS, thereby contributing to the significant mechanical improvement. Structurally, DNE has a hierarchically interpenetrated double-network, resulting in no obvious nanofibrous orientation (Fig. 2I and Supplementary Fig. 10). Compared with SNE, the enhanced mechanical property of DNE reveal the advantages of the hierarchically interpenetrated networks.

We further analyzed the average size of crystallites by fitting SAXS profiles, which affords a radius of gyration (Rg) of ~7.0 nm for 20PP–DNE, that is, nanocrystalline dimension (D) of ~7.0 nm (Fig. 2J, K). According to the SAXS profiles plotted with Lorentz correction, the interdomain spacing (L) is obviously reduced in progressive manufacturing procedures, revealed from the shift of qmax to the high-q region (Supplementary Fig. 11 and Fig. 2K)26,27. Taken together, these observations allow us to confirm the nanocrystalline morphology: salting out and solvent substituting significantly facilitate the nucleation and refinement of nanocrystalline domains, and mechanical training constructs long-range ordered nanocrystalline domains as constructing the hierarchical structures. Collectively, combined with the described above in mechanical performances and structural evolution, these experimental findings allow us to draw conclusions: structural transitions occur at multiple length scales including hierarchically interpenetrated networks, hierarchical nanofibrils and nanocrystalline domains, and intermolecular interactions resulting in energy dissipation multimechanisms from molecular to mesoscopic scales, and contributing to the improved mechanical performance of DNE, in terms of strength, stretchability and toughness (Fig. 3L and Supplementary Note 1).

Ionic transport resistances and ion-electron coupling of PIEgels
Having elucidated the mechanical properties behind the structure reconfiguration, we proceeded to investigate how DES as solvents and PEDOT:PSS as conductive polymer affect the electrochemical performances of PIEgels. We engineered PIEgels via incorporating electrically conductive and ionically conductive components into a gel matrix to achieve piezovoltage generation and efficient transmission under the pressure stimulus. Therefore, we investigated ionic transport resistances and ion-electron coupling using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements.

We fabricated a series of coin batteries assembled by PIEgels electrolyte (Size: 12 mm diameter×2 mm thickness) and Zn anode/cathode as blocking electrode for electrochemical measurements (Fig. 3A). In ion-electron mixed PIEgels, electronic and ionic charge carriers do not display the same polarization phenomena, neither the same transport kinetics. EIS allows identifying the contributions of those two charge carriers to the ionic conductivity using established equivalent circuit analysis, involving electronic conduction pathway and ionic conduction pathway (Fig. 3B). EIS plots show two semicircles: one depressed semicircle at lower frequency and a segment of a greater semicircle within the higher frequency region, which indicates two kinds of conduction, respectively, electronic and ionic28,29. The impedance of PIEgels is measured over a frequency range of 10–1–10–6 Hz and the EIS analysis is represented in the form of Nyquist plots and Bode plots. In the Randles circuit model, the electronic and ionic resistance of PIEgels (Re and Ri) shows high correlations with PEDOT:PSS. In contrast to 0PP–DNE, the Re and Ri of 10PP–DNE increase, whereas they substantially decrease for 20PP–DNE, suggesting the ion-electron coupling. Furthermore, Nyquist plots and Bode plots of 20PP–DNE exhibit the characteristic electrochemical behavior of ionic conductor, with notable lower resistance and higher σ indicating exceptional ionic transmission (Fig. 3C–H and Supplementary Fig. 13).

These equivalent circuit outcomes reaffirm that ionic conduction is the predominant factor in the PIEgels, reflecting in the fact that the conductivity of PIEgels is dominated by ionic conductivity. As the PEDOT:PSS content increases, the Re and Ri of the eutectogel exhibits a markedly coupling than that of the hydrogel, while Re and Ri initially increased and subsequently decreased. Conversely, upon transformation of the eutectogel into a hydrogel via solvent exchange, Re and Ri plummets (Fig. 3I, Supplementary Figs. 14 and 15). These findings highlight the predominant influence of the PEDOT:PSS and DES on Re and Ri. While the intrinsic ionic conductivity of DES may contribute marginally, the observed dramatic fluctuations of Re and Ri is more likely attributable to the ion-electron coupling effect. Specifically, ion-exchange between PEDOT:PSS and Na+ or Cl−. The PEDOT facilitates Cl− transport through hole-polaron interactions, while the −SO3− on PSS chain electrostatically interact with Na+, synergistically enabling ion exchange that significantly delivers an order-of-magnitude-improved electrical performance (Fig. 3J). To validate the ion-exchange mechanism, the free energy of ion exchange ΔGIE between PEDOT:PSS, Na+ and Cl− is calculated from the standard Gibbs free energy (ΔG0) of each species, using density functional theory (DFT) calculations, before and after the ion exchange16:

ΔGIE = ΔG0(PEDOT+Cl−) + ΔG0(Na+PSS−) − ΔG0(PEDOT:PSS) − ΔG0(Na+) − ΔG0(Cl−) (1)

where, Cl− and Na+ function as distinct species rather than NaCl pairs. This distinction arises because Na+ originates solely from NaCl pairs, while Cl− derives from both NaCl pairs and the ChCl component of the DES. (Fig. 3J and Supplementary Fig. 16). The strongly negative ΔGIE (−317.7 kJ mol−1) signifies highly favorable ion exchange kinetics, likely enabled by Cl− and Na+ acting as charge carriers within the PIEgels16,17. Additionally, we also investigated the electrochemical stability based on CV curves, scan rate of 100 mV s−1 (Fig. 3K, Supplementary Figs. 17 and 18). Compared with other eutectogels and hydrogels, 20PP–DNE exhibits negligible changes in repeated CV curves, suggesting superior electrochemical stability against charging and discharging 200 cycles, and the stable ion-electron coupling formed via the ion-exchange reaction. Furthermore, 20PP–DNE has a higher charge storage capacity in comparison to 10PP–DNE and 0PP–DNE, suggesting highly advantageous in flexible electronic devices and applications30,31.

Piezoionic performances and piezoionic coefficients of PIEgels
Piezovoltage is identified as the pressure-induced ion streaming potentials, probably resulting from a preferential displacement of the cation (Na+) over anion (Cl–) between hierarchical nanofibrils and resulting in a positive voltage output for PIEgels. We designed an indentation experiment to apply mechanical force stimulations in which the applied pressure and generated piezovoltage were measured. Applying force is analogous to pressing into skin using a finger or other object. As shown in Fig. 4A, a single PIEgels unit consists of two separated electrodes, attached to the force sensor on the premise of electrostatic shielding, and applied mechanical forces via the linear motors. Importantly, the pressure region covers the piezoelectric to avoid stress concentration and uniform piezoionic ion diffusion in the whole bulk. Interestingly, PEDOT:PSS has an effect on differential ion flows, with a positive or negative correlation via ion exchange, which has been confirmed by conductivity and electrochemical measurements. Therefore, we primarily attributed the piezoionic behavior to the electron-conducting-assisted ion transmission, integrated the hierarchical network, probably resulting in a rapid hierarchical migration of Na+ (Fig. 4B). Indeed, piezovoltage originates from the diffusivity difference of Na+ ions and Cl– ions under pressure. The greater the diffusivity difference of cation and anion, the higher the mechanosensitivity and piezovoltage10,11.

We observed the piezovoltage output by continuously applying step force stimulations. Particularly, the mechanosensitivity (S) during applying pressure and inactivation time (T) during removing pressure of 20PP–DNE, respectively, shows 1457 mV s–1 and 2.569 s, corresponding to piezoionic coefficient of 9.7 nV Pa–1 and piezovoltage (4 V) of 30 mV (Fig. 4C, D and Supplementary Fig. 19A). The S and T of 10PP–DNE, respectively, is 9.8 mV s–1 and 0.841 s, corresponding to piezoionic coefficient of 1.9 nV Pa–1 and 4 V of 5.8 mV (Fig. 4E, F and Supplementary Fig. 19B). Whereas the S and T of 0PP–DNE respectively is 900 mV s–1 and 0.485 s, corresponding to piezoionic coefficient of 2.6 nV Pa–1 and 4 V of 7.9 mV (Fig. 4G, H and Supplementary Fig. 19C). These experimental findings confirms that 20 wt% PEDOT:PSS substantially promotes the piezoionic ion diffusion kinetics in applying pressure, accompanied by substantial ion inactivation kinetics after removing pressure, whereas 10 wt% hinder ion diffusion kinetics, in comparison to PIEgels without PEDOT:PSS. This correlation further confirms that PEDOT:PSS is capable of altering ionic conduction via ion-exchange reaction, which is dependent on the concentration (Supplementary Fig. 20). Furthermore, the variation trend of piezoionic performance with the PEDOT:PSS concentration is consistent with the electrochemical properties.

To further manifest piezoionic coefficients in response to pressure of PIEgels, we further measured the piezovoltage output performances under different pressures. In comparison to the covered force stimulus for piezoionic ion diffusion in the whole bulk, the localized pressure to manifesting piezoionic coefficients (Fig. 4I). The piezoionic coefficient (α) is the slope of the pressure (4P) and piezovoltage (4V) curves. Under a small pressure input of 0–1 MPa, the magnitude of piezovoltage is almost zero, indicating that no voltage is generated. A positive close-to-linear correlation between 4P and 4V under pressure input 1–5 MPa, with the higher degree of pressure was accompanied by a rapid increase in the piezovoltage output, from 0 to 47 mV, and piezoionic coefficient of 10.9 nV Pa–1. As the pressure continues to increase, the piezovoltage increases slowly with a low piezoionic coefficient of 1.44 nV Pa–1 (Fig. 4J, K, Supplementary Figs. 21 and 22). These findings have important implications for our understanding of the trade-off between mechanical robustness and piezoionic effect—that is, the hierarchical network not only supports the mechanical properties, but also orients the ion transport pathways – that is, along hierarchical nanofibrous rather than in space, reducing the energy barrier for ion transmission.

Structural and molecular determinant of piezoionic mechanism
Given the concept of synergistic design, the piezoionic mechanism of pressure-induced piezovoltage in PIEgels is derived from structural advantages and molecular coupling. The mechanosensitivity (S) during pressure application reflects the piezoionic activation kinetic, while the inactivation time (T) upon pressure release characterizes their inactivation kinetics.

Structurally, the hierarchically nanofibrous network constructed achieves the confinement of pressure-driven ion flux, producing the uniform orientation of ion migrations. Compared with isotropic three-dimensional networks, this structure potentially reduces the spatial energy barrier for ion migration, thereby facilitating ion transmission. Compared to non-hierarchical PIEgels, those with hierarchical structures exhibit a 3.6-fold increase in ΔV, a 3.5-fold enhancement in piezoionic coefficient, and a 2.2-fold improvement in S. However, they require a 22-fold longer T. These findings indicate that the hierarchical architecture facilitates greater ion migration, producing the optimized inactivation kinetics. (Fig. 5A and Supplementary Fig. 23).

Molecularly, to elucidate the role of DES on piezoionic performance, we immersed PIEgels in both NaCl solution and water, transforming them into hydrogels. Notably, this transition leads to a substantial deterioration in piezoionic properties, with a more pronounced reduction observed in water. These findings unequivocally demonstrate the dominant role of DES in maintaining piezoionic activation and inactivation kinetics, consistent with its function in electrochemical properties. Furthermore, these observations may suggest a beneficial role of Na+ in piezoionic performance (Fig. 5B and Supplementary Fig. 23). Therefore, we conducted comparative experiments that revealed significantly inferior piezoionic performances in eutectogels containing either NaCl or PEDOT:PSS alone, compared to the integrated PIEgels. Notably, NaCl-free and PEDOT:PSS-free eutectogels exhibit dramatically shortened the T, with the 49-fold and 5.3-fold reduction compared to PIEgels, respectively. These compelling evidences establish the pivotal role of ion-electron coupling in governing piezoionic activation and inactivation kinetics, contributing to exceptional, continuous piezoionic output (Fig. 5C and Supplementary Fig. 24).

The ion diffusion mechanism in electrical doping has been clearly revealed that the electronic gating occurs via Na+/Cl– inserted or removed from PEDOT:PSS-binding site, in which Na+ and Cl– are the charge-compensating species of PEDOT:PSS32,33. To further elucidate the ion-electron coupling effect, we performed DFT calculations that revealed strong bonding interactions between PEDOT and Cl− (‒142.7 kJ mol‒1), as well as between PSS and Na+ (‒309.1 kJ mol‒1). In contrast, the bonding energies of PEDOT‒Na and PSS‒Cl are only as low as ‒36.4 kJ mol‒1 and ‒37.9 kJ mol‒1, respectively. These computational results demonstrate the existence of a robust charge compensation via the ion-exchange reaction between NaCl and PEDOT:PSS. Furthermore, the PSS‒PVA interaction exhibits a binding energy (‒135.5 kJ mol‒1) second only to the PEDOT‒PSS bonding (‒173.6 kJ mol‒1), and approximately twice that of PVA‒PEDOT (‒63.9 kJ mol‒1). This pronounced energy differential establishes PSS as a preferential interfacial intermediary, bridging PVA chains and PEDOT backbones to form pressure-responsive hierarchal networks (Figs. 3J and 5D–F, Supplementary Figs. 26–28). Further explorations of structure transitions using Raman spectroscopy provide solid evidence for investigating the conformational transitions of PEDOT from a benzenoid structure (disordered coil conformation) to a quinoid structure (ordered linear conformation) before and after applying pressure. Additionally, XPS analysis reveals a significant increase in the binding energy of Na+ and Cl− ions under applied pressure, demonstrating the electron transport chain propagation via ion-exchange reactions34–36.

Collectively, these findings indicate that the ion-electron coupling effect enables dynamic charge compensation via ion exchange between PEDOT:PSS and Na+/Cl−, while simultaneously boosting the pressure-driven ion activation and inactivation kinetics.

Comprehensively, these observations allow us to draw a clear demonstration of the molecular origins of piezoionicity in PIEgels, namely, hierarchical network orientation and charge compensation mechanism (Fig. 5K). On the one hand, hierarchical architecture facilitates greater ion migration by lowering the spatial energy barriers of ion transport. On the other hand, the charge compensation mechanism dynamically modulates ionic diffusion kinetics by leveraging pressure. The charge compensation mechanism operates through an ion-exchange reaction. Additionally, although the ion-exchange reaction is thermodynamically spontaneous, sufficient concentrations of both ions and electrons are required to ensure favorable reaction kinetics. Mechanistically, Cl–, as the main charge-compensating species of the holes on the PEDOT backbone, extends the electronic transmission chain and further accelerates Na+-ion transmission in response to an applied pressure. Additionally, nanoconfined Cl– ions struggle to migrate, providing a significant enhancement in the diffusivity difference between Na+ ions and Cl– ions, and contributing to high-performance piezovoltage output. Whereas removing pressure, Na+ binding sites on the −SO3− moieties on the PSS chains are activating to retard Na+-ion reverse migration, thereby facilitating ion inactivation kinetics and further guaranteeing the continuous pressure-driven piezovoltage output.

Piezoionic diffusion kinetics via molecular dynamics simulation
The piezoionic effect arises from pressure-driven ionic mobility difference of cations and anions. Previous reports have also shown that the mobile ions are intrinsically subject to a hydrodynamic drag force and the counter ions' mobility, leading to a gradual quenching of the piezoionicity even if the action time of force is prolonged. At this point, the mobile ions are either not migrating or are balanced by counter ion migration10,11. Therefore, to investigate the underlying mechanism of continuous piezoionicity, we employed molecular dynamics (MD) simulations to gain mechanistic insights into piezoionic diffusion kinetics of PIEgels (Fig. 6A, B). The simulation systems in our work contain 10 PVA chains, 10 PEDOT:PSS chains, 30 NaCl molecules and sufficient DES molecules (light cyan region) (Supplementary Fig. 36). Furthermore, informed by the piezoionic mechanism—which relies on the collaboration between hierarchical structure and charge compensation—we computationally designed and realized a simulation system featuring such a hierarchical architecture. Another critical contribution is charge compensation arising from ion-exchange reactions; therefore, we performed MD simulations with varying numbers of NaCl to probe reaction kinetics. As the number of NaCl molecules increased from 30 to 60, Na+ and Cl− ions migrate simultaneously, yet with temporally alternating mobility, resulting in a partial offset of their opposing contributions. These simulation results indicate a kinetically unfavorable ion-exchange reaction due to the increased ion number, thereby disrupting the charge compensation mechanism (Supplementary Figs. 37 and 38).

As indicated by the square and oval regions in Fig. 6A, the applied pressure facilitates rapid interlayer migration of Na+ ions (purple) during the initial 0–2.5 ns timespan, whereas their motion slows markedly upon pressure release within 2.5–5 ns. This transport phenomenon attests to the highly asymmetric ion diffusion kinetics within PIEgels, underlying the continuous piezoionicity (Supplementary Note 2). During compression, the MSD of both Na+ and Cl− ions was markedly higher than that observed during pressure release, clearly demonstrating accelerated ion migration under applied mechanical stress (Fig. 6C). To further elucidate the characteristics of piezionic diffusion kinetics, we quantified the diffusion coefficient through mean-squared-displacement (MSD) calculations. Specifically, we investigated the piezoionic kinetics by monitoring the time-dependent diffusion coefficients. During the initial 0–1 ns period, the diffusion coefficients of both Na+ and Cl− ions remain near-zero, indicating that the applied pressure is insufficient to drive ion differential migration. The absence of ΔD between the cationic and anionic diffusion coefficients precludes the piezovoltage generation. Subsequently, as the applied pressure is progressively increased over a time scale of 1–2 ns, the acceleration of ion transmission is accompanied by a rapid increase in diffusion coefficients, contributing to a progressively enlarging ΔD, with 0.38×10–12 cm–2 s–1 at 2 ns (i.e., 1.60×10–12 cm–2 s–1 for Na+ ions and 1.22×10–12 cm–2 s–1 for Cl− ions). During the final 2–2.5 ns period, ion differential migration decelerates despite further increases in pressure, accompanied by a concomitant reduction in ΔD with 0.18×10–12 cm–2 s–1 at 2.5 ns (i.e., 1.84×10–12 cm–2 s–1 for Na+ ions and 1.66×10–12 cm–2 s–1 for Cl− ions). In summary, the piezoionic dynamics observed in our MD simulations are in agreement with the experimentally measured piezovoltage and piezoionic coefficients across varying pressures, as shown in Fig. 4J. Following the release of pressure at 2.5–5 ns, ion migration decelerated markedly, accompanied by a substantial decrease in ionic diffusion coefficients. Interestingly, however, the diffusion coefficient of Cl− ions (i.e., 0.19×10–12 cm–2 s–1 at 4.0 ns) exceeded that of Na+ (i.e., 0.15×10–12 cm–2 s–1 at 4.0 ns), indicating preferential confinement of Na+ ions after releasing the pressure, a finding consistent with both experimental spectroscopies and DFT calculations (Fig. 6D, E).

Collectively, MD simulation further corroborates piezoionic characteristics and the underlying synergistic mechanism for PIEgels, demonstrating the pronounced asymmetry in the diffusion kinetics for decoupling the continuous pressure-driven ion migration. Such behavior—where the electromechanical coupling is activated only under sufficient pressure stimulation—stems from the synergistic effects of well-organized ion migration within a hierarchical structure and efficient charge compensation between ion and electron. Finally, we leveraged PIEgels to construct a prototype device that generates piezovoltage under mechanical stimulation, highlighting amenability as a modular component for self-powered devices and monitoring movements (Fig. 6F and Supplementary Note 3).

Methods
Preparation of DES
Glycerol (Gly, J&K Scientific Ltd, 99%) as a hydrogen bond donor and choline chloride (ChCl, J&K Scientific Ltd, 98%) as a hydrogen bond acceptor were mixed in a predetermined molar ratio of 2:1, and followed by stirring for 1 h at 60 °C and sonicating for 30 min (Branson M1800) until achieving homogeneity and transparency.

Preparation of DES-based covalently precursor solution
The predetermined monomer containing acrylamide (AAm, J&K Scientific Ltd, 99%) and acrylic acid (AAc, J&K Scientific Ltd, 98%), covalent cross-linker N,N’-methylenebisacrylamide (MBAA, J&K Scientific Ltd, 98%) and photo-initiator 2-Hydroxy-4′-(2-hydroxyethoxy)−2-methylpropiophenone (Irgacure 2959, Sigma Aldrich, 98%) were mixed with above-described DES by stirring for 3 h at 60 °C, followed by bubble removal with an ultrasonic bath (Branson M1800) for 30 min. The obtained solution was the as-prepared DES-based covalent precursor solutions.

Fabrication of physically single-network PVA/PEDOT:PSS hydrogel
Firstly, PEDOT:PSS aqueous solution (Clevios PH1000, Heraeus) was filtered by a PTFE syringe-driven filter (0.45 μm, Jet Bio-Filtration Co., Ltd.) to make 10 wt% and 20 wt% aqueous solutions under vigorous stirring. Then, polyvinyl alcohol (PVA, Sigma Aldrich, 99+% hydrolyzed) powder was dissolved in PEDOT:PSS aqueous solution under vigorous stirring with an oil bath at 90 °C for 2 h to make a 10 wt% solution. After cooling to room temperature, the obtained solution was poured into a glass mold with a thickness of 2 mm, and was frozen first in a refrigerator at −20 °C for 24 h to synthesize prefabricated PVA/PEDOT:PSS hydrogel. After that, the resultant sample is thawed at 40 °C for 3 h. The thawed sample is refrozen in a refrigerator at −20 °C for 24 h and thawed again at 40 °C for 3 h to repeat six times freeze-thawing process. Finally, the resultant freeze-thawed sample was immersed in was soaked in 2 M NaCl solution for 24 h to obtain PVA/PEDOT:PSS hydrogel.

Fabrication of mechanically trained DNE
The PVA/PEDOT:PSS hydrogel prepared above was immersed in pre-prepared DES at 25 °C at the scheduled time of 6 h to conduct solvent substitution, and formed a single-network PVA/PEDOT:PSS eutectogel. To fabricate the prestreched PVA/PEDOT:PSS eutectogel, the PVA/PEDOT:PSS eutectogel was stretched to controlled strain of 150% and maintained for 10 min. After that, the prestreched PVA/PEDOT:PSS eutectogel was further immersed preprepared covalently precursor DES solutions containing AAm and AAc of 4 M as monomer, 0.01 mol% MBAA, and 0.01 mol% I-2959 at 30 °C for 24 h. The covalent network of eutectogel was formed by UV light-initiated radical polymerization with a wavelength of 365 nm, and completed within 10 min, to obtain mechanically trained DNE.

Fabrication of mechanically trained double-network hydrogel
The mechanically trained DNE prepared above were immersed pre-prepared 2 M NaCl solution and pure water at 30 °C for 24 h to conduct solvent exchange, to obtain a mechanically trained double-network hydrogel.

Characterization of eutectogels
The morphologies and elemental mapping of various gels were characterized on a SEM (FESEM, QUANTA FEG 650, FEI, USA), equipped with an energy-dispersive X-ray analysis system. XPS (K-Alpha X, Thermal Scientific, USA) was used to determine the element composition of the various gels. The chemical components of gels were investigated by FTIR spectra using a Fourier transform infrared spectrometer (FTIR, V70, Brooker, Germany). The chemical structure of PEDOT:PSS was analyzed by Raman spectroscopy (LabRAM HR Evolution, Horiba, Japan).

Temperature-variable IR measurement
For sample preparation, a small quantity of gel was placed between two ZnSe tablets and compressed into an ultrathin film for transmission IR measurement on a Nicolet iS50 FTIR spectrometer. The tablets were sealed with Parafilm and subjected to a temperature gradient from 20 to 200 °C at intervals of 10 °C for the acquisition of temperature-variable IR spectra.

Two-dimensional correlation spectroscopy
The temperature-variable transmission FTIR spectra of various polymer gels, acquired from 20 to 200 °C, were used for performing 2D correlation analysis. 2D correlation analysis was carried out using the software, 2D Shige ver. 1.3 (©Shigeaki Morita, Kwansei Gakuin University, Japan, 2004–2005) and further plotted into contour maps by OriginPro 2021. In the contour maps, red colors are defined as positive intensities, while blue colors as negative ones.

Mechanical properties characterization
The mechanical properties of the polymer gels were mainly evaluated via standard stress-strain experiments by using a testing machine (Shimadzu AGS-X-5000 N). The whole sample is machined into a cylindrical shape for tensile tests. Both ends of the dumbbell-shaped sample were connected to the clamps, with the lower clamp fixed. The testing rate was set at 50 mm min−1. Young’s modulus (E [MPa]) was determined from the initial slope of the stress-strain curves. Fracture strengths (Ef [MPa]) were appointed to represent the stresses at which the ultimate tensile failure occurs in the uniaxial tensile test. Toughness (Γ [MJ m−3]), a mechanical parameter that characterizes the work required to fracture the sample per unit, was obtained by integrating the area below the stress-strain curve until fracture. Each mechanical test was repeated with at least three individual samples.

Electrochemical characterization and fittings
All electrochemical measurements were carried out on a Potentiostat/Galvanostat/Zero resistance ammeter (Interface 1000E, Gamry) at room temperature (25 °C). EIS measurements conducted over a frequency range of 0.1 Hz and 100 kHz and an amplitude of 10 mV, and CV measurements at the potential window of ±0.5 V and scan rate of 100 mV s−1 were performed in coin batteries assembled by PIEgels electrolyte and Zn anode/cathode. To examine the ionic conduction behavior of the PIEgels, the Nyquist plots are then analyzed by means of equivalent circuit fitting using the EIS spectrum analyzer software28,29. In the analysis of ionic conduction, we used the Randle equivalent circuit, with Ri representing ionic resistance and Cdl representing double-layer capacitance. Parallel to the double-layer capacitance, we considered the diffusion impedance due to the faradaic reaction, consisting of the charge transfer resistance Rct and the Warburg impedance Zw. We treated ionic resistance and electronic resistance as independent, leading to Re and Ri arranged in parallel. Ionic conductivity is calculated using the expression:

σ = L/(SRi) (2)

where L represents the electrode distance (cm), S is the cross-sectional area of the sample (cm2), and R is the body resistance (Ω) extracted from the equivalent circuit fitting, i.e., R=ReRi/(Re+Ri). The PIEgels measure ~12 mm in diameter and 2 mm in thickness, with the thickness serving as the electrode distance. Gamry Echem Analyst software (version 6.3) was used for fitting the circuit models to the impedance data.

Electronic conductivity measurements were carried out using a low resistivity meter (LORESTA GP, Model MCP-T610, Mitsubishi Chemical Corporation) based on the 4-terminal 4-pin method. PSP probes with 1.5 mm in interelectrode distance were chosen to measure the electrical conductivity of PIEgels. Specifically, in the case of the 4-pin probe method, 4 needle-type electrodes are placed linearly on a sample surface, a certain current I flows between 2 external pin probes, and a potential difference V formed between 2 inner pin probes is measured to determine the resistance R. Then, multiplying the measured resistance R with the sample thickness t and the resistivity correction factor (RCF) derives the volume resistivity ρv, where RCF was obtained by determining the coordinates of the point to be measured using low resistivity meter. All samples were cut into round pieces (12 mm in diameter and 2 mm in thickness). The conductivity σ is calculated by:

σ = 1/ρv = V × RCF × t−1 (3)

SAXS and WAXS measurement
To quantify the dimension, structure, and evolution of nanocrystalline domains during the fabrication, X-ray scattering measurements were carried out on a modified Xeuss system (Xenocs 2.0, France) equipped with a semiconductor detector (Pilatus 3R 100K, DECTRIS, Switzerland) using Cu Kα radiation. Quantification of 2D SAXS and wide-angle X-ray scattering (WAXS) patterns was performed with scattering vector (q) and azimuthal angle (2θ) as coordinates. The wavelength of the X-ray radiation was 0.154 nm. The inter-crystal spacing (L), crystal dimension (D) of nanocrystalline domains were calculated according to the 1D scattering profiles.

SAXS was used to characterize the inter-crystal spacing and the average crystal dimension. The average distance between adjacent crystalline domains L can be estimated from the scattering maxima corresponding to the peak intensity qmax according to the Bragg expression:

L = 2π/qmax (4)

where scattering vector (q) is defined as:

q = 4π sinθ/λ (5)

where λ is the x-ray wavelength, and 2θ is the scattering angle.

The average crystal dimension was obtained by the radius of gyration (Rg), and calculated by applying the Guinier equation in the Guinier region:

I(q) = I(0) exp(−q2Rg2/3) (6)

qRg ≪ 1

where I(0) is the zero angle scattering intensity and Rg is used to represent the size of PVA crystal structure.

Piezoionic response and electromechanical transduction measurement
The indentation experiment to apply mechanical force stimulations, where the applied pressure and generated piezovoltage were measured instantaneously. A single tested PIEgels unit consists of two separated electrodes, attached to the force sensor (Simbatough, SBT291) on the premise of electrostatic shielding, and applied mechanical forces via the linear motors (LinMot, BF01-37). Mechanical forces were programmed through the time-displacement motion profiles in LinMot-Talk 6 configuration software, and measured by assembling a strain gauge signal conditioning amplifier (Interface, SGA/A) to the force sensor, and transferred to a digital input/output device with high channel isolation (National Instruments, PCI-6251) using the connectors (National Instruments, BNC2110). The time-displacement motion profiles were defined as trapezoidal and sinusoidal perturbations, in which the acting time of the trapezoidal perturbation is longer than that of the sinusoidal perturbation. For characterizing piezoionic coefficients in response to applied pressure, time-displacement motion profiles were employed sinusoidal perturbation to apply force stimulation. Whereas time-displacement motion profiles were utilized with a trapezoidal perturbation to apply pressure for characterizing the pressure-induced ion diffusion kinetics. The piezoionic coefficient was obtained from the time-piezovoltage graph using the following equation:

Piezoionic coefficient = 4V/4P (7)

where 4V is the peak piezovoltage, 4P is the applied pressure. The mechanosensitivity (S) was obtained from the time-piezovoltage graph using the following equation:

S = 4V/t (8)

where t corresponds to the time at which the peak piezovoltage occurs during applying pressure.

DFT simulation
DFT optimizations and calculations were performed using Gaussian 09 software. Becke’s three-parameter hybrid exchange function, the Lee-Yang-Parr correlation function (B3LYP) was employed to investigate binding energies, and 6–31G(d) basis set was chosen for C, H, O, N and Cl atoms. All the molecules were separately constructed, geometrically optimized and energy calculations. The energy difference was obtained by subtracting the total energy of the system from the energy of each component in the complexes, reflecting the intermolecular interactions energy:

4E A−B = Etotal − EA + EB (9)

MD simulation
The PVA chains and PEDOT:PSS chains were constructed using Visual Molecular Dynamics (VMD) software, consisting of 30 and 6 repeating units, respectively. The simulation system containing 10 PVA chains and 10 PEDOT:PSS chains was established using VMD software37, along with 30 NaCl molecules. The DES solvent contents were maintained consistent with the experimental conditions. The size of the simulation box is 16.68 nm (X direction)×5.98 nm (Y direction)×9.00 nm (Z direction). All MD simulations were carried out using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) software package38, employing the OPLS-AA force field applicable to choline chloride-based DESs. And the OPLS-AA force field parameters were adopted from Professor Orlando Acevedo at the University of Miami39.

Prior to the formal simulation, the simulation system underwent a two-stage equilibration process: Firstly, the 1 ns relaxation under the NPT ensemble at 298.15 K; Subsequently, the 2 ns relaxation under the NVT ensemble at the same temperature, to achieve a stable and physically reasonable configuration. In a typical MD simulation procedure, two graphene plates, as a pressure applicator, each 5.5 nm in length, were placed at the upper and lower boundaries along the Z direction of the simulation box. A constant velocity of 1 nm ns−1 was applied to the graphene plates along the Z direction to simulate the compression of the PIEgels, which lasted for 2.5 ns. Afterward, the external pressure was removed, and the simulation system was allowed to evolve freely for an additional 2.5 ns. The integration time step was set to 1 fs throughout the simulation. Of note, periodic boundary conditions (PCBs) were applied in the X and Y directions, while the Z direction employed non-PCBs.

The diffusion coefficient of Na+ ions and Cl– ions could be quantitatively determined using the MSD data derived from MD simulations. The diffusion coefficient was calculated by employing the well-adopted Einstein’s relation:

Di = lim t→∞ MSD(t)/2nt (10)

where D represents the diffusion coefficient, n represents the dimensionality of the system, which is 3 for a three-dimensional system, and t denotes the time over which the MSD was calculated.

MSD is defined by the equation:

MSD = 1/N ∑i 〈|ri(t + t0) − ri(t0)|2〉 (11)

where N is the number of ions, 〈〉 denotes the ensemble average, ri(t + t0) and ri(t0) represent the positions of ions at time 0 and t, respectively.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The manuscript by Xu et al. presents the development and characterization of a novel conductive eutectogel system based on PVA, PEDOT:PSS, and sodium p-styrenesulfonate (SNE) within a eutectic solvent. The authors report that this material exhibits enhanced mechanical robustness, high ionic and electronic conductivity, and, notably, a continuous piezoionic effect, generating electrical signals in response to mechanical deformation. The study demonstrates the potential application of this eutectogel in flexible sensors for monitoring human motion and pressure distribution. The concept of achieving continuous piezoionicity in a robust, conductive eutectogel is interesting and potentially significant for stretchable electronics and human-machine interfaces. However, substantial revisions are required to clarify the underlying mechanisms, strengthen the experimental evidence, and address several critical points regarding the material's properties and performance before it can be considered for publication.\n\nMajor Comments\n1. Novelty and Context: While the eutectogel system is presented, its novelty should be clearly articulated in the context of existing conductive gels (hydrogels, organogels, ionogels) and piezoionic/piezoelectric materials. Please modify the sentence to highlight the specific advantages of the PEDOT:PSS/PVA/SNE eutectogel over prior work in terms of performance (sensitivity, linearity, bandwidth), stability, processability, or the underlying mechanism itself. A more thorough comparison with relevant literature is required.\n2. Elaboration on the Piezoionic Mechanism: The core claim of the manuscript revolves around \"continuous piezoionicity-driven electromechanical coupling.\" While a mechanism involving stress-induced ion redistribution facilitated by PEDOT:PSS conductive pathways is proposed (Fig. 4I), it requires more detailed justification and stronger supporting evidence.\nPlease provide a more in-depth explanation of how mechanical stress specifically leads to the proposed ion gradients and charge separation within the eutectogel structure.\n3. Electrochemical Stability in Ionic Environments: The manuscript highlights a remarkable electrical conductivity (~29.09 S cm⁻¹, Fig. 1G) of the 20 wt% PEDOT:PSS eutectogel, underscoring its promise in bioelectronics. However, crucial data on long-term stability under mechanical strain and in ionic-rich conditions (DES, residual NaCl) are currently missing. PEDOT:PSS is known to suffer conductivity degradation due to ionic interactions, redox processes, or mechanical fatigue. Therefore, performing cyclic compression tests (e.g., over 1,000 cycles) and utilizing XPS to evaluate PEDOT oxidation states after electrochemical cycling would clarify potential degradation mechanisms. Additionally, a discussion addressing potential ionic–electronic conductivity trade-offs and how electronic conduction is sustained despite high ionic content would considerably strengthen the manuscript’s technical rigor and application relevance.\n4. Piezoionic Charge Compensation Mechanism: The claim that Cl⁻ acts as a charge-compensating species for PEDOT holes (Fig. 4I) lacks direct evidence. No data on ionic mobility ratios (D+/D−) or selective ion permeation are provided. Potentiostatic intermittent titration (PITT) should be used to quantify Na⁺/Cl⁻ diffusion coefficients, and ion-selective electrode measurements during compression would clarify Cl⁻’s role in charge compensation. Without this validation, the proposed piezoionic mechanism remains speculative.\n5. Structural Evolution and Crystallinity Correlation: The WAXS/SAXS data (Fig. 2B–E) show increased crystallinity but fail to quantitatively correlate mechanical training with nanocrystalline alignment. The 19.5° peak intensity increase could indicate crystallite alignment rather than size changes. Azimuthal integration of 2D SAXS patterns would quantify nanofibril orientation, while Scherrer analysis of crystallite dimensions could link structural evolution to tensile properties. These analyses are essential to substantiate the hierarchical network’s role in mechanosensitivity.\nThe manuscript presents a potentially valuable contribution by exploring piezoionicity in conductive eutectogels. However, significant revisions are necessary to address the major concerns outlined above, particularly regarding the mechanistic explanations for piezoionicity and modulus enhancement, potential limitations in conductivity, interpretation of structural data, and demonstration of long-term stability. Addressing these points with further experiments, analysis, and clarification will substantially strengthen the manuscript and improve its suitability for publication.", "reviewer_2": "This manuscript reports a mechanically trained strategy to fabricate robust piezoionic eutectogels with hierarchical structure, followed by comprehensive characterization and performance evaluation. The proposed eutectogels exhibit piezoionic output while maintaining excellent mechanical properties. However, the manuscript suffers from a lack of rigorous and supported scientific explanation, with complicated/meaningless assertions throughout. Several key concepts and mechanisms are insufficiently supported by effective data, which significantly weaken the scientific credibility of this work. Compared to previous reports, the piezoionic performance of the eutectogels appears inferior. Given these concerns, the manuscript is not suitable for publication in Nature Communication.\n1. For a scientific paper, it is very necessary to be concise and easy to understand. The Introduction and Results sections contain excessive details, including discussions that are not related to the core concept of this manuscript. In addition, the core challenge is not extracted in the Introduction, and the proposal of this work is too far-fetched. This manuscript focuses on the structural design of eutectogel and the evaluation of piezoionic output, so there is no need for extensive discussions on biological tissues and PIEZO2 protein in the Introduction. In the Discussion section, the authors fully characterized and explained the eutectogels, but most of the detailed explanations seem to be irrelevant to the core mechanism, and the conclusions are too sudden and unconvincing. I strongly suggest the authors to re-edit the manuscript by refining the theoretical framework, strengthening the supporting data, and removing unnecessary descriptions. There is also an excessive amount of self citation.\n2. The development of eutectogels with piezoionic effects is a key highlight of this study. However, the term “eutectiogel” here does not seem to be appropriate. Similar to glycerol, acrylic acid and acrylamide are common hydrogen bond donors, and their inclusion disrupts the hydrogen bond donor-to-acceptor ratio in the system. The authors should critically assess whether the prepared system qualifies as a deep eutectic solvent. The validity of the eutectogel in this system remains uncertain.\n3. While the concept of eutectogel is repeatedly emphasized, the manuscript lacks a clear explanation for its necessity. Furthermore, the authors do not provide explicit reasons for selecting specific materials, such as PEDOT:PSS instead of other conjugated polymers, or choline chloride (ChCl) instead of other quaternary ammonium salts. These choices are crucial for optimizing piezoionic performance, yet they are not justified in the manuscript.\n4. The authors claim that pre-stretching induces the formation of oriented PVA nanocrystals, which serve as channels for directional ion transport. However, the 2DWAXS and SAXS results do not exhibit clear crystal orientation, contradicting the data presented in Figure 1D. Furthermore, the assertion that PVA nanocrystals forms non-porous walls lacks sufficient experimental support. Even if such a non-porous and oriented crystalline structure exists, the mechanism by which it facilitates selective ion diffusion remains unexplored, and no reasonable experimental validation is provided as well.\n5. The study presents an insufficient range of PEDOT:PSS ratios, making it difficult to derive a meaningful correlation between PEDOT:PSS content, mechanical properties, and piezoionic performance. Moreover, the bonding interactions between PEDOT:PSS and PVA during the freeze-thaw and photocuring processes remain unclear, despite being a crucial aspect of the material system. The authors should provide a more systematic investigation into these factors.\n6. The manuscript states that “PEDOT:PSS has an effect on for differential ion flows, with a positive or negative correlation depending on the content, which has been confirmed by conductivity and electrochemcial” and “we primarily attributed the piezoionic behavior to the presence of conducive polymer in PIEgel”. However, those claims are not adequately supported by experimental data. Additionally, it is unclear whether the electronic conductivity of PEDOT:PSS influences piezoionic performance. Further investigation and clarification are necessary.\n7. The authors rely on SEM images to analyze the phase separation, crystallinity, molecular chain network changes, and even bonding within the eutectogels. These imprecise analyses lead to low credibility of the relevant conclusions. In the infrared spectroscopy analysis, no in-situ FTIR data is provided, making statements such as \"during the self-assembly process\" inappropriate. Moreover, the use of 2D correlation spectroscopy (2DCOS) to analyze infrared spectra under temperature fluctuations is unrelated to piezoionic performance under pressure. The authors should provide a more precise and relevant spectroscopic analysis.\n8. The methodology for piezoionic testing is unclear. According to Figures 4a and 4b, it is difficult to establish a pressure gradient between the two electrodes, raising concerns about the source of the anion-cation diffusion difference. Additionally, the applied pressure reaches the MPa range, while the corresponding force is only in the N range, necessitating further clarification of the experimental setup. The observed baseline is unstable, which further weakens the reliability of the results. To prove the stability, I strongly recommend the authors to conduct test at least 1000 cycles.\n9. The conductivity of reported eutectogel (~29 S cm⁻¹) is extraordinarily high, surpassing many inorganic materials. The authors should provide detailed explanations regarding the measurement and calculation methods to justify this exceptional value. Additionally, the measured resistance values appear to be inconsistent with the reported current densities. More comprehensive testing and validation are required.\n10. The manuscript describes a conductive device based on a series configuration. However, this structure does not seem to be suitable for piezoionic applications. Further explanation is needed to justify the device design. In addition, the demonstration of this device in the manuscript is not related to biosensors, and therefore cannot support the bioelectronic application mentioned by the authors.\n11. The manuscript contains numerous confusing terms, such as \"piezoionicity-induced mechanotransduction\", \"piezoionic diffusion\", \"electromechanical coupling\", \"hysteretic intermediate\", \"piezoionicity-induced mechanotransduction\". Overall, readability is low, with certain sections having contradictory statements. The manuscript should be thoroughly revised, and professional language editing is strongly recommended.", "reviewer_3": "In this manuscript, a double crosslinked network of piezoionic eutectogels (PIEgels) with hierarchical nanofiber networks is designed to solve the problem of voltage decay of conventional piezoelectric materials under long-term pressure by enhancing the mechanical properties of the materials and optimizing the ion transport paths. Earlier studies by Madden group and Derek Ho group demonstrated piezoionic hydrogels capable of achieving mechanoelectrical coupling via pressure-driven ion flux. Notably, these hydrogels with high mechanical sensitivity are intrinsically required to produce substantial piezoionic output, yet they are mechanically soft.This work demonstrates that rational molecular and structural design enables the realization of piezoionic effects in mechanically robust gels, while maintaining exceptional piezoionic output performance. Overall, this study innovatively combines mechanical robustness with piezoionicity, a breakthrough likely to attract significant interest in related fields. The comments and suggestions are as follows:\n1. Mechanistically, the superior piezoionic output of PIE gels arises from their hierarchical architecture and charge compensation mechanism. The hierarchical structure restricts the direction of ion flow, so could this phenomenon be demonstrated by in situ characterization techniques or molecular dynamics simulations to visualize the migration path of ions more intuitively? In addition, the molecular-scale charge compensation mechanism, which may be a novel concept to this study, demands further elucidation.\n2. The conductivity and piezoionic output of the material exhibit consistent trends relative to PEDOT:PSS. What underlying mechanistic link exists between these parameters? The authors are advised to elaborate on this correlation.\n3. As shown in Figures 4E and 4G, 10PP-DNE exhibits no enhancement in piezoionic performance compared to 0PP-DNE, while its mechanical sensitivity declines significantly. The underlying mechanism driving this counterintuitive phenomenon warrants detailed elucidation, yet the manuscript currently lacks explicit discussion of this critical observation.\n4. In terms of mechanical properties, materials should be considered for mechanical fatigue testing under long-term cyclic loading. In addition to mechanical stability, does the effect of ion transport degrade at different temperatures?\n5. Does 'S'in Figure 4 stand for mechanical sensitivity? This is not stated. Similar to 'T' and 'V'. In addition, V should be changed to ∆V.\n6. Line 417-423, 'When there is no mechanical energy to sustain these movements, PEDOT:PSS exerts a constraint on Na+ in which Na+ is bound to the SO3– groups on the PSS, increasing the transfer energy barriers and generating the ion inactivation kinetics. Critically, this ion diffusion mechanism in electrical doping have been clearly revealed that the electronic gating occurs via ions inserted or removed from PEDOT:PSS-binding sites in ordered PEDOT-rich regions, in which Na+ ions and Cl− ions are the charge-compensating species at matched ionic and electronic concentrations.' : If there could be further elaboration on this sentence, it would be beneficial."}, "author_response": "Point-by-Point Response to Reviewers' Comments\nDear Reviewers:\nWe deeply appreciate your time and effort in reviewing our manuscript and providing constructive\nfeedback on our manuscript entitled “Continuous piezoionicity-driven electromechanical coupling in\nmechanically robust conductive eutectogels (NCOMMS-25-18534)”. Thank you very much for the\nencouraging comments that help to strengthen the quality of our manuscript. In response to these\nvaluable comments, we provide point-by-point responses along with the modifications made in the\nrevised manuscript and supplementary information, and marked in the red color. We sincerely hope\nthat the revised manuscript now meets the standards for publication.\nThank you very much for your help in improving this research. Thank you for your kind consideration!\nIn this response letter below,\n Response to Reviewer #1: Page 02 – 25\n Response to Reviewer #2: Page 26 – 52\n Response to Reviewer #3: Page 53 – 67\nPlease note that:\n Reviewers' comments are in blue color.\n Authors’ responses are in black color.\n1 / 67\n Reviewer #1:\nThe manuscript by Xu et al. presents the development and characterization of a novel conductive\neutectogel system based on PVA, PEDOT:PSS, and sodium p-styrenesulfonate (SNE) within a\neutectic solvent. The authors report that this material exhibits enhanced mechanical robustness, high\nionic and electronic conductivity, and, notably, a continuous piezoionic effect, generating electrical\nsignals in response to mechanical deformation. The study demonstrates the potential application of\nthis eutectogel in flexible sensors for monitoring human motion and pressure distribution. The\nconcept of achieving continuous piezoionicity in a robust, conductive eutectogel is interesting and\npotentially significant for stretchable electronics and human-machine interfaces. However,\nsubstantial revisions are required to clarify the underlying mechanisms, strengthen the experimental\nevidence, and address several critical points regarding the material's properties and performance\nbefore it can be considered for publication.\nWe greatly appreciate you for meticulous review and intriguing comments, which has helped us to\nfurther improve our manuscript and research value. We have seriously taken the reviewers’\nsuggestions into account and carefully revised our manuscript.\nComment 1A. Novelty and Context: While the eutectogel system is presented, its novelty should be\nclearly articulated in the context of existing conductive gels (hydrogels, organogels, ionogels) and\npiezoionic/piezoelectric materials.\nAuthors’ Response: We sincerely appreciate your valuable suggestions. The comparison of\npiezoionic eutectogels with other polymer gels/piezoelectric materials is crucial. Therefore, we have\nimplemented the following modifications:\nJust as you suggested, this work mainly achieved the piezoionic effect in the eutectogel (PIEgels). In\nterms of mechanical and piezoionic perfoemances, it surpasses the currently reported piezoionic\nhydrogels, which mainly relies on the synergistic design of the structural and the molecular\nengineering. We will explain to you from the following three aspects (why eutectogel?):\n(1) Conductive gels. Ionogels/eutectogels achieve high ionic conductivity via mobile ions in ionic\nliquids/deep eutectic solvents (ILs/DESs), whereas hydrogels/organogels depend on dissolved\nelectrolytes. This inherent ionic conduction in network is more beneficial for piezoionic materials.\nFurthermore, eutectogels bridge the gap between sustainability (DESs) and functionality (ILs-like\nproperties), enabling the broadly adjustable electronic and electrochemical window. For piezoionics,\neutectogels have smaller-radius ions, such as chloride ions (Cl−), which are more sensitive to pressure\ncompared to larger-molecular-weight ionic compounds in ionogels (Table R1).\n(2) Hierarchical structure. In PIEgels, we designed a hierarchical structure to reduce the spatial\nenergy barrier for ion migration, thereby forming pressure-driven oriented ion stemming. We\nconstructed the hierarchical structure using mechanical training, owing to its efficiency, that is, the\nsingle pre-stretching training. Compared with hydrogels or ionogels, eutectogels can achieve more\nefficient mechanical training (Nat. Commun. 2025,16, 2589. https://doi.org/10.1038/s41467-025-\n57800-y; Adv. Mater. 2024, 36, 2304145. https://doi.org/10.1002/adma.202304145) (Table R1).\n3. Thermostability. Deep eutectic solvents (DES), as hydrogen-bonding supramolecular complexes,\nmanipulate the interaction, conformation, and structure of polymer networks, giving mechanical\nproperties such as self-healing (Angew. Chem. Int. Ed. 2023, 62, e202313971), strong and tough and\nother physical properties such as temperature-resistance (Adv. Mater. 2024, 36, 2309576).\nThe reported piezovoltage of piezoionic materials are usually transient, meaning that the generated\nvoltage disappears along with the removal of the pressure. PIEgels possesses continuous pressure-\ninduced electrical generation owing to negligible vapor pressure of DES, lasting for over 200 seconds.\nThis requires that the gel itself possess extremely outstanding mechanical properties and\nthermostability to prevent mechanical failure caused by continuous applied pressure (Table R1).\nTable R1. Comparison of the mechanical training of this work with others strong and tough polymer\ngels reported in the literature.\nPolymer gels Solvents Conductivity Hierarchical structure Thermostability Ion species\nHydrogels HO Not intrinsic Cyclic mechanical training Poor No ions\nIonogels Ionic liquids Intrinsic, ionic Cyclic mechanical training Depends on solvent Larger ions\nEutectogels Deep eutectic solvents Intrinsic, ionic Single mechanical training Outstanding Smaller ions\nWe also made the corresponding changes in the Introduction of Revised manuscript (marked with\nred color) and Supplementary Information (Supplementary Table 1), as follow:\nIntroduction:\n(Line 45) Piezoionic/piezoelectric materials: Piezoelectric materials can convert mechanical forces\ninto electrical signals, whereas piezoionic materials tend to be based on the movement of ions rather\nthan electrons in response to pressure gradients. Consequently, piezoionic materials, like electric\norgans, are regarded as a very good match for biosensings and biointerfaces.\n(Line 59) Obviously, mechanically weak piezoionic mechines, i.e., hydrogels, fail to render the\ncontribution to continuous ionic currents production in response to mechanical forces, along with\nmechanical failure under persistent loading, i.e., crown ether grafted PVA hydrogel as differential\namplifier, zwitterionic hydrogels as piezoionic device with a mobile-ion-free system and piezoionic\nelastomers with ionic plastic crystal.\nComment 1B. Please modify the sentence to highlight the specific advantages of the\nPEDOT:PSS/PVA/SNE eutectogel over prior work in terms of performance (sensitivity, linearity,\nbandwidth), stability, processability, or the underlying mechanism itself. A more thorough\ncomparison with relevant literature is required.\nAuthors’ Response: We sincerely appreciate you for valuable feedback. Below, we provide a detailed\nresponse to the advantages of the PIEgels. We modified the performance and mechanism to highlight\nthe unique features of PIEgels. In short, the PIEgels, capability of seamlessly compatible integration\nof remarkable mechanical properties and outstanding piezovoltage output, is engineered via\nsynergistic methodologies in molecular and structural engineering. Therefore, the advantages of\nPIEgels mainly lie in two aspects: mechanical and piezoionic performances and piezoionic\nmechanism.\n(1) Performance: By integrating conductive polymer and progressive manufacturing procedures, the\nresultant PIEgels exhibit satisfactory mechanical properties and outstanding conductivity,\ncontributing to the orientated, continuous pressure-driven ion steaming for producing piezovoltage\noutput, with peak generated voltage of averaged 40 mV at 3.0 MPa (Mechanosensitity: 1457 mV s–\n1), and with lasting for over 200 seconds. These outstanding piezoionic performances is attributed to\nthe considerable mechanical properties. The Young’s modulus, fracture strength and work of rupture\nof PIEgels are 21.72 ± 1.50 MPa, 23.53 ± 0.78 MPa and 42.39 ± 1.60 MJ m–3, respectively. In short,\nthese comprehensive performances are far superior to that of the currently reported piezoionic gel\nmaterials (Figure R1 and Table R2).\n(2) Piezoionic mechanism: Structurally, PIEgels present hierarchically interpenetrating networks\nengineered via mechanical training, accelerating ionic conduction via directional transport of ion\nsteaming and improving ionic transmission via lower spatial barriers in hierarchical networks.\nMolecularly, conductive polymer poly(3,4-ethylenedioxythiophene) doped with\npoly(styrenesulfonate) (PEDOT:PSS) is regarded as charge-compensated receptor of NaCl to\nimprove mechanosensitivity, contributing to diffusion and inactivation kinetics of Na+ transmission.\nWhen applying pressure, the Cl−-to-hole binding in PEDOT skeletons substantially promotes the\ndiffusion kinetics of Na+, resulting in considerable mechanosensitivity; whereas the Na+-to-(−SO –)\n3\nbinding in PSS chains facilitate inactivation kinetics, leading to the continuous piezovoltage when\nremoving the pressure. Benefiting from the outstanding synergistic effect in molecular and structural\nengineering, i.e., hierarchical structure and charge compensation mechanism, the resulting PIEgels\ncombine remarkable mechanical robustness and piezoionic effects (peak piezovoltage of 40 mV at\n3.0 MPa), and serve as continuous pressure-driven ion migration to generate piezoionic output of\nabout 200s.\n4 / 67\nFigure R1. Piezoionic performances of the PIEgels. (A) Piezovoltage responses under repeated step compressions\nat a pressure of ~ 3.0 MPa. (B) The force‒time curves corresponding to piezovoltage responses in Figure R1A. (C)\nComparison chart in the Ashby plot of Young’s modulus versus peak piezovoltage of PIEgels with other reported\npiezoionic hydrogels. (D) Comparison chart in the Ashby plot of fracture strength versus peak piezovoltage of\nPIEgels with other reported piezoionic hydrogels.\nTable R2. Comparison of the mechanical properties and piezoionic effect of this work with others\npiezoionic gels reported in the literature.\nReferences Mechanical performances Piezoionic effect\nYoung’s Fracture stress Piezovoltage Piezoionic Mechano-\nmodulus coefficient sensitivity\n(MPa) (mV)\n(MPa) (nV Pa–1) (mV s-1)\nThis work 21.72 ± 1.50 23.53 ± 0.78 40 (3.0 MPa) 9.8 1457\nAngew, 2025 1 0.32 ~ 1.2 4 (100 KPa) 5.0 13.7\nScience, 2022 2 N/A N/A 2.8 (360 KPa) 8.0 N/A\nJ. Am. Chem. Soc., 2025 3 ~ 0.1 ~ 0.6 ~ 17.5 N/A N/A\nAdv. Funct. Mater., 2025 4 0.43 ± 0.01 1.55 ± 0.07 44.35 (50 KPa) 0.89 N/A\nNano Energy, 2025 5 ~ 0.05 ~ 0.2 27.3 N/A N/A\nAdv. Funct. Mater., 2023 6 ~ 0.05 1.27 13.08 1780 N/A\n5 / 67\nWe also made the corresponding changes in the Introduction and Results in the Revised manuscript\n(marked with red color) and Supplementary Table 1 in the Revised Supplementary Information, as\nfollow:\nIntroduction:\n(Line 64) Challenges and Processability: Whereas the mechanosensitivity and ionic transmission\nmay be sluggish in mechanically strong piezoionic gels owing to the weak pressure gradient caused\nby stress concentration. Therefore, a persistent challenge lies in balancing the structural requirements\nand molecular designs in soft piezoionics for integrating remarkable mechanosensitivity, ionic\ntransmission, and mechanical robustness, to produce continuous, stabilized pressure-driven ion flux.\nAdvances in strategies for establishing or designing the synergistic methodology from molecular and\nstructural engineering perspectives has contributed to an explosion of personalized polymer gel.14\nDespite the supportive contributions of mechanical performances in realistic application scenarios,\nits synergism with functionality remains largely unknown owing to the incompatibility or mismatch\nbetween accessible performances and functionalities. To this end, we envisioned that the synergistic\ndesigns of molecular and structural engineering is an ideal orthogonal manufacturing technology to\nmake mechanosensitive, mechanically strong piezoionic gels.\n(Line 77) Underlying mechanism: Structurally, PIEgels present hierarchically interpenetrating\nnetworks engineered via mechanical training, accelerating ionic conduction via directional transport\nof ion steaming and improving ionic transmission via lower spatial barriers in hierarchical networks.\nMolecularly, conductive polymer poly(3,4-ethylenedioxythiophene) doped with\npoly(styrenesulfonate) (PEDOT:PSS) is regarded as charge-compensated receptor of NaCl to\nimprove mechanosensitivity, contributing to diffusion and inactivation kinetics of Na+ transmission.\nWhen applying pressure, the Cl−-to-hole binding in PEDOT skeletons substantially promotes the\ndiffusion kinetics of Na+, resulting in considerable mechanosensitivity; whereas the Na+-to-(−SO –)\n3\nbinding in PSS chains facilitate inactivation kinetics, leading to the continuous piezovoltage when\nremoving the pressure. Benefiting from the outstanding synergistic effect in molecular and structural\nengineering, i.e., hierarchical structure and charge compensation mechanism, the resulting PIEgels\ncombine remarkable mechanical robustness and piezoionic effects (peak piezovoltage of 40 mV at\n3.0 MPa), and serve as continuous pressure-driven ion migration to generate piezoionic output of\nabout 200s.\nMolecular and structural design of mechanically robust PIEgels:\n(Line 130) Performance: By integrating conductive polymer and progressive manufacturing\nprocedures, the resultant PIEgels exhibit satisfactory mechanical properties and outstanding\nconductivity, contributing to the orientated, continuous pressure-driven ion steaming for producing\n6 / 67\npiezovoltage output, with peak generated voltage of averaged 40 mV at 3.0 MPa. (Fig. 1G and\nSupplementary Fig. 3). The resultant PIEgels achieve the integration of exceptional mechanical\nperformances and piezovoltages, outperforming some reported piezoionic hydrogels (Fig. 1H, 1I and\nSupplementary Table 1).\nFigure R2. Revised Figure 1 in Manuscript.\nComment 2. Elaboration on the Piezoionic Mechanism: The core claim of the manuscript revolves around \"continuous piezoionicity-driven electromechanical coupling.\" While a mechanism involving stress-induced ion redistribution facilitated by PEDOT:PSS conductive pathways is proposed (Fig. 4I), it requires more detailed justification and stronger supporting evidence. Please provide a more in-depth explanation of how mechanical stress specifically leads to the proposed ion gradients and charge separation within the eutectogel structure.\n7 / 67\nAuthors’ Response: Thank you for your valuable insights. The validation and explanation of the\npiezoionic mechanism were inadequately addressed. To rectify this, we systematically incorporated\ncontrol experiments and DFT optimization to comprehensively elucidate the piezoionic mechanism.\nThe ionic currents generated by piezoionic matrices in response to mechanical force occur either by\nstreaming a single polarity of ions or by one polarity of ions being preferentially carried over the\ncounterions through the polymer matrix, enabling a net charge imbalance (Science 376, 502-507\n(2022).DOI:10.1126/science.aaw1974). As highlighted, hierarchical architecture is indeed critical for\npiezoionic performance—an aspect previously unexplored in our work. To address this gap, we\nengineered a non-hierarchical eutectogel and systematically characterized its piezoelectric properties.\nStructurally, the hierarchically nanofibrous network constructed achieve the confinement of pressure-\ndriven ion flux, producing the uniform orientation of ionic migrations. Compared with isotropic three-\ndimensional networks, this structure potentially reduces the spatial energy barrier for ionic migration,\nthereby facilitating ion gradients.\nFigure R3. The influence of hierarchical structure on the piezoionic performances. (A and B) The piezovoltage\noutput by continuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and\nion inactivation kinetics (B) for trained 20PP–DNE. (C and D) The piezovoltage output by continuously applying\nstep force stimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for\nuntrained 20PP–DNE.\n(1) Ion gradients. Particularly, the mechnosensitivity (S) during applying pressure and inactivation\ntime (T) during removing pressure of 20PP–DNE (No trained) respectively shows 651 mV s–1 and\n0.116s, corresponding to piezoionic coefficient of 2.6 nV Pa–1 and piezovoltage (∆V) of 7.8 mV. The\n8 / 67\nmechnosensitivity (S) during applying pressure and inactivation time (T) during removing pressure\nof 20PP–DNE respectively shows 1457 mV s–1 and 2.569s, corresponding to piezoionic coefficient\nof 9.7 nV Pa–1 and piezovoltage (∆V) of 30 mV. Therefore, 20PP–DNE exhibit a 3.6-fold increase\nin ∆V, a 3.5-fold enhancement in piezoionic coefficient, and a 2.2-fold improvement in S. However,\nthey require a 22-fold longer T. These findings indicate that the hierarchical architecture facilitates\ngreater ion migration, producing the remarkable inactivation kinetics (Figure R3 and Figure R4).\nFigure R4. Comparison of piezoionic performances between trained and untrained 20PP–DNE. (A) Piezovoltage\nand piezoionic coefficient. (B) mechanosensitivity and inactivation time.\n(2) Charge separation.\n(A) Piezoionic experiment. To investigate charge separation mechanisms, we engineered a NaCl-\nfree eutectogel containing exclusively chloride ions (sourced from the choline chloride component of\nthe deep eutectic solvent). We anticipated substantially degraded piezoionic performances in NaCl-\nfree eutectogel due to the absence of sodium-mediated charge compensation between Na+ and PSS\nin PEDOT:PSS.\nThe mechnosensitivity (S) during applying pressure and inactivation time (T) during removing\npressure of 20PP–DNE without NaCl respectively shows 342 mV s–1 and 00.052s, corresponding to\npiezoionic coefficient of 2.5 nV Pa–1 and piezovoltage (∆V) of 7.5 mV. Therefore, 20PP–DNE exhibit\na 4.0-fold increase in ∆V, a 3.9-fold enhancement in piezoionic coefficient, and a 4.3-fold\nimprovement in S. However, they require a 49-fold longer T. These findings indicate that Na+ In the\nNaCl-free eutectogel, mechanosensitivity originates solely from chloride ion migration. Compared to\nNaCl-containing PIEgels, this system exhibits significantly attenuated mechanosensitivity (1457 mV\ns–1) and inactivation time (2.569 s). This strongly indicates that Na+, with their smaller ionic radius,\nserve as the primary charge carriers in PIEgels, enabling enhanced mechanosensitive responses\nthrough efficient charge-compensated migration (Figure R5 and Figure R6).\n9 / 67\nFigure R5. The influence of Na+ on the piezoionic performances. (A and B) The piezovoltage output by\ncontinuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and ion\ninactivation kinetics (B) for 20PP–DNE with NaCl. (C and D) The piezovoltage output by continuously applying\nstep force stimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for\n20PP–DNE without NaCl.\nFigure R6. Comparison of piezoionic performances between 20PP–DNE with NaCl and 20PP–DNE without NaCl.\n(A) Piezovoltage and piezoionic coefficient. (B) mechanosensitivity and inactivation time.\n(B) DFT calculation. To validate the charge separation mechanism, the free energy of ion exchange\nΔG between PEDOT:PSS, Na+ and Cl− is calculated from the standard Gibbs free energy (ΔG0) of\nIE\neach species, using density functional theory (DFT) calculations, before and after the exchange:\nΔG = ΔG0(PEDOT+Cl−) + ΔG0(Na+PSS−) − ΔG0(PEDOT:PSS) − ΔG0(Na+) − ΔG0(Cl−)\nIE\nwhere, Cl− and Na+ function as distinct species rather than NaCl pairs. This distinction arises because\nNa+ originates solely from NaCl pairs, while Cl− derives from both NaCl pairs and the ChCl\n10 / 67\ncomponent of the DES. The strongly negative ΔG (−317.7 kJ mol−1) signifies highly favorable ion\nIE\nexchange kinetics, contributing the charge separation between Na+ and Cl− (Figure R7).\nFigure R7. Schematic illustration of DFTcalculations for the standard Gibbs free energy (ΔG0) of each species, i.e.,\nCl−, Na+, PEDOT:PSS, PEDOT+Cl−, and Na+PSS−.\nFigure R8. The molecular origins of piezoionicity in conductive, hierarchical PIEgels for applying pressure (top)\nand removing pressure (bottom). Na+ ions and Cl– ions are the charge-compensating species of PEDOT:PSS,\nachieving dynamic modulation of piezoionic activation/inactivation kinetics via pressure-responsive switching.\n11 / 67\nWe also made the corresponding changes in the Piezoionic mechanism of structural and molecular\ndeterminant and Figure 5 in the Revised manuscript, and Supplementary Fig. 15 and Supplementary\nFig. 22 in Revised Supplementary Information.\nComment 3A. Electrochemical Stability in Ionic Environments: The manuscript highlights a\nremarkable electrical conductivity (~29.09 S cm-1, Fig. 1G) of the 20 wt% PEDOT:PSS eutectogel,\nunderscoring its promise in bioelectronics. However, crucial data on long-term stability under\nmechanical strain and in ionic-rich conditions (DES, residual NaCl) are currently missing.\nAuthors’ Response: Thank you for your valuable insights. Electrochemical stability plays a decisive\nrole in determining the practical applicability of PIEgels. Following your insightful suggestions, we\nsystematically evaluated their stability in ionic environments through controlled immersion\nexperiments. Specifically, PIEgels were immersed for 24 hours in: (i) pure deep eutectic solvent\n(DES), maintaining their eutectogel state (named as DES–24H), and (ii) 2M NaCl aqueous solution,\ninducing transformation into hydrogel (named as NaCl–24H). Subsequent electrochemical\ncharacterization revealed distinct stability profiles between these two systems (Figure R9).\nThe impedance of DES–24H and NaCl–24H is measured over a frequency range of 10–1 – 10–6 Hz\nand the EIS analysis is represented in the form of Nyquist plots and Bode plots. In the Randles circuit\nmodel, the electronic and ionic resistance of PIEgels (R and R) shows substantially decrease in\ne i\ncomparison with PIEgels. Critically, the hydrogel transition triggers a substantial conductivity decreas,\nunequivocally demonstrating DES's indispensable role in maintaining electrochemical functionality.\nCollectively, these findings reveal fundamental stability limitations of PIEgels in ion-rich\nenvironments: (i) aqueous media induce solvent exchange-driven hydrogel conversion, while (ii)\nDES immersion compromises performance through disruption of ion-exchange kinetics via\ncompetitive interference from extrinsic ions (Figure R10).\nConsequently, PIEgels demonstrate fundamental limitations for implantable bioelectronics due to\nperformance degradation in physiological environments. While their instability precludes reliable in\nvivo operation, these materials remain promising candidates for flexible electronics operating in ex\nvivo settings.\nFigure R9. Optical characterization of PIEgels following 24-hour immersion. (Left) PIEgels in deep eutectic\nsolvent (DES) maintains structural integrity. (Right) Phase transition to hydrogel occurs in 2M NaCl solution,\n12 / 67\ndemonstrating environment-dependent matrix reorganization.\nFigure R10. (A) Nyquist plots of NaCl–24H. These symbols are measured experimentally, and dashed lines are\nobtained by fitting using an equivalent circuit model. (B) Bode plots with impedance and phase angle of NaCl–24H.\n(C) Nyquist plots of DES–24H. These symbols are measured experimentally, and dashed lines are obtained by\nfitting using an equivalent circuit model. (D) Bode plots with impedance and phase angle of DES–24H. (E) The\nconductivity of NaCl–24H, DES–24H, and the original. (F) Ionic conductivity (σ) and electrical conductivity (σ )\ni e\nof NaCl–24H, DES–24H and the original determined from the impedance spectra by equivalent circuit fitting\nanalysis.\nWe also made the corresponding changes in the Electrochemical performances and conductive\nmechanism of PIEgels in the Revised Manuscript and Supplementary Fig. 14 in Revised\nSupplementary Information.\nComment 3B. PEDOT:PSS is known to suffer conductivity degradation due to ionic interactions,\n13 / 67\nredox processes, or mechanical fatigue. Therefore, performing cyclic compression tests (e.g., over\n1,000 cycles) and utilizing XPS to evaluate PEDOT oxidation states after electrochemical cycling\nwould clarify potential degradation mechanisms.\nAuthors’ Response: We value your expert insights, particularly regarding the critical role of long-\nterm operational stability in practical applications. To comprehensively assess the long-term stability\nof PIEgels, we performed extended cycling tests across three critical performance metrics:\nelectrochemical behavior (200 cycles), mechanical performances (＞ 1000 cycles), and piezoionic\nperformances (uninterrupted 700 cycles).\n(1) Electrochemical behavior. Cyclic voltammetry over 1,000 cycles revealed stable charge storage\ncapacity during the initial 200 cycles, followed by a progressive enhancement in subsequent cycles\n(Figure R11). This performance evolution likely stems from dynamic regulation of the ion-exchange\nreaction, where repeated electrochemical stimulation optimizes charge-compensated ion migration\npathways.\nFigure R11. Cyclic voltammograms (CV) profiles of 20PP–DNE during 1000 cycles.\n(2) Mechanical performances. Cyclic compression tests at 50% strain reveal pronounced energy\ndissipation during cycles 2-100, followed by stabilization with negligible dissipation and hysteresis\nsaturation beyond 2 cycles (Figure R12). This demonstrates exceptional mechanical resilience\nthrough 1,000 compression cycles, establishing a robust mechanical foundation for continuous\npressure-induced piezoionic performance.\n14 / 67\nFigure R12. (A) Stress‒strain curves of 1000 consecutive compression -relaxation cycles for 20PP–DNE at strain\nof 50% (B) related hysteresis values. The curves are horizontally shifted for clarity.\n(3) Piezoionic performances. Under continuous 3 Hz cyclic compression at 2 MPa stress, the\npiezovoltage output maintained stable operation for 220 seconds before undergoing significant\nattenuation. Beyond this duration, the output voltage decayed to 50% of its peak piezovoltage\namplitude, with the system enduring > 700 compressive cycles while preserving pressure-induced\npiezovoltage output (Figure R13).\nFigure R13. (A) Piezovoltage response stability of individual PIEgels under successive step acting force with\nsinusoidal perturbations. (B) Typical force‒time curves under repeated step compressions at a pressure of ~ 2.0\nMPa. PIEgels size: 0.7 cm × 0.7 cm × 1.5 mm. (C) Raman spectrum of PIEgels before (top) and after (bottom)\napplying pressure. Raman spectrum demonstrates a structural transition of PEDOT:PSS from benzoid to quionoid\nconformation, indicating the extension of the PEDOT electronic chain.\nWe also made the corresponding changes in the Structural and molecular determinant of piezoionic\nmechanism and Figure 5 in the Revised Manuscript, as well as Supplementary Fig. 17 and Fig. 30 in\nRevised Supplementary Information.\nComment 3C. Additionally, a discussion addressing potential ionic–electronic conductivity trade-\noffs and how electronic conduction is sustained despite high ionic content would considerably\nstrengthen the manuscript’s technical rigor and application relevance.\n15 / 67\nAuthors’ Response: We sincerely appreciate your expert guidance, which rightly identified the\npreviously underexplored electrochemical mechanisms. To address this, we implemented a\ncomprehensive validation strategy integrating experimental characterization and DFT optimization\nfor the evolution process of conductivity.\nThrough systematic comparative experiments, we mapped the evolution of ionic and electronic\nconductivities as functions of PEDOT:PSS content and solvent composition, conclusively\ndemonstrating the ion-electron coupling effect (Figure 14A). Complementarily, DFT-optimized\nstructures revealed a substantial negative Gibbs free energy change (ΔG = −317.7 kJ/mol) for the ion-\nexchange reaction between PEDOT:PSS and Na+/Cl−, confirming its thermodynamic spontaneity and\nhighlighting its critical role in enhancing piezoionic performances (Figure 14B).\nFigure R14. (A) The evolution process of ionic conductivity (σ) and electrical conductivity (σ ) determined from\ni e\nthe impedance spectra by equivalent circuit fitting analysis. (B) Schematic illustration of conductive mechanism of\nPIEgels and the ion exchange reaction between PEDOT:PSS and Na+/Cl− in PIEgels.\nThe principal modifications in the Electrochemical performances and conductive mechanism of\nPIEgels and Figure 3 in the Revised Manuscript, as well as Supplementary Fig. 13 and Supplementary\nFig. 15 in Revised Supplementary Information.\n16 / 67\n(Line 245) As the PEDOT:PSS content increases, the ionic conductivity of the eutectogel exhibits a\nmarkedly stronger upward trend than that of the hydrogel, while the electrical conductivity undergoes\na slight decline before rising. Conversely, upon transformation of the eutectogel into a hydrogel via\nsolvent exchange, its ionic conductivity plummets (Fig. 3I and Supplementary Fig. 14). These\nfindings highlight the predominant influence of the DES on the conductivity. While the intrinsic ionic\nconductivity of DES may contribute marginally, the observed dramatic enhancement is more likely\nattributable to the ion-electron coupling effect, specifically ion exchange between PEDOT:PSS and\nNa+ or Cl−. The PEDOT facilitates Cl− transport through hole-polaron interactions, while the −SO –\n3\non PSS chains electrostatically interact with Na+, synergistically enabling ion exchange that\nsignificantly delivers an order-of-magnitude-improved electrical performances (Fig. 3J).\nThe Revised Figure 3 in the Revised Manuscript:\nComment 4. Piezoionic Charge Compensation Mechanism: The claim that Cl⁻ acts as a charge-\n17 / 67\ncompensating species for PEDOT holes (Fig. 4I) lacks direct evidence. No data on ionic mobility\nratios (D+/D−) or selective ion permeation are provided. Potentiostatic intermittent titration (PITT)\nshould be used to quantify Na⁺/Cl⁻ diffusion coefficients, and ion-selective electrode measurements\nduring compression would clarify Cl⁻’s role in charge compensation. Without this validation, the\nproposed piezoionic mechanism remains speculative.\nAuthors’ Response: As you rightly emphasized, the diffusion coefficient is critically important.\nHowever, unfortunately, our extensive review of prior research revealed a lack of methodologically\nsound approaches for its calculation. Initially, Prof. Madden and colleagues characterized self-\ndiffusion coefficient determination using in situ Nuclear magnetic resonance (Science 376, 502-507\n(2022). DOI:10.1126/science.aaw1974), which presents significant practical challenges for our study.\nFurthermore, diffusion coefficients derived from methods like PITT, GITT, and EIS fitting primarily\nreflect the diffusion of redox-active species within the electrodes (e.g., lithium in lithium-ion\nbatteries), rather than the diffusion of chloride (Cl⁻) and sodium (Na⁺) ions within the PIEgels\nelectrolyte itself. Consequently, to indirectly probe the disparity in diffusion between Na⁺ and Cl⁻\nions within the gel, we employed a combination of corroborative control experiments and DFT\ncalculations. While we have included diffusion coefficient values obtained from electrochemical\nfitting for reference, we explicitly express caution regarding their interpretation. These values do not\nrepresent the intrinsic diffusion of ions within the bulk electrolyte phase.\n(1) Confirmatory experiment. We engineered a NaCl-free eutectogel containing exclusively\nchloride ions (sourced from the choline chloride component of the deep eutectic solvent). The\nmechnosensitivity (S) during applying pressure and inactivation time (T) during removing pressure\nof 20PP–DNE without NaCl respectively shows 342 mV s–1 and 00.052s, corresponding to piezoionic\ncoefficient of 2.5 nV Pa–1 and piezovoltage (∆V) of 7.5 mV. Therefore, 20PP–DNE exhibit a 4.0-fold\nincrease in ∆V, a 3.9-fold enhancement in piezoionic coefficient, and a 4.3-fold improvement in S.\nHowever, they require a 49-fold longer T. These findings indicate that Na+ In the NaCl-free eutectogel,\nmechanosensitivity originates solely from chloride ion migration. Compared to NaCl-containing\nPIEgels, this system exhibits significantly attenuated mechanosensitivity (1457 mV s–1) and\ninactivation time (2.569 s). This strongly indicates that Na+ – with their smaller ionic radius – serve\nas the primary charge carriers in PIEgels, enabling enhanced mechanosensitive responses through\nefficient charge-compensated migration (Figure R15C and Figure R15D).\nAdditionally, PIEgels were immersed for 24 hours in: (i) 2M NaCl aqueous solution and (ii) pure\nwater, inducing transformation into hydrogel (named as NaCl–24H and H\nin NaCl solution, the system transformed into a hydrogel via solvent exchange, thus containing no\nCl− from DES. Similarly, after immersion in pure water, it also transformed into a hydrogel, with no\nNa+ and Cl− present in the system. Significantly, the piezoionic performance of both hydrogels\ndecreased substantially, with the H O–24H sample exhibiting a more pronounced decline (Figure\n2\n18 / 67\nR15C to Figure R15H). This indicates that NaCl is an essential component for generating piezoionic\noutput. Furthermore, in the absence of chloride ions from DES, the diffusion difference between the\ntwo systems becomes negligible, resulting in lower piezovoltage. It also reflects the absence of an\nion-exchange-mediated charge compensation mechanism without DES. These control experiments\ndemonstrate that the Cl⁻ ions in DES, rather than those from NaCl, are the primary species responsible\nfor the charge compensation mechanism.\n19 / 67\nFigure R15. The influence of Na+ on the piezoionic performances. (A and B) The piezovoltage output by\ncontinuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and ion\ninactivation kinetics (B) for 20PP–DNE with NaCl. (C and D) The piezovoltage output by continuously applying\nstep force stimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for\n20PP–DNE without NaCl. (E and F) The piezovoltage output by continuously applying step force stimulation (E)\nand corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (F) for NaCl–24H. (G and H) The\npiezovoltage output by continuously applying step force stimulation (G) and corresponding piezoionic ion diffusion\nkinetics and ion inactivation kinetics (H) for H O–24H.\n2\n(2) DFT calculations. To elucidate the ion-electron coupling effect, we performed DFT calculations\nthat revealed strong bonding interactions between PEDOT and Cl− (‒142.7 kJ mol‒1), as well as\nbetween PSS and Na+ (‒309.1 kJ mol‒1). In contrast, the bonding energies of PEDOT‒Na and PSS‒\nCl are only as low as ‒36.4 kJ mol‒1 and ‒37.9 kJ mol‒1, respectively. These computational results\ndemonstrate the existence of a robust charge compensation mechanism via the ion exchange reaction\nbetween Na+/Cl– and PEDOT:PSS (Figure R16).\nFigure R16. (A) Electrostatic potential distribution of PEDOT and PSS obtained by density functional theory (DFT)\noptimizations. (B) Comparison of interaction energy between conductive polymer PEDOT:PSS and ionic\ncomponents Na/Cl by DFT optimizations. (C) Structure of PEDOT–Cl, PEDOT–Na, PSS–Cl and PSS–Na obtained\nDFT optimizations.\n(3) Diffusion coefficient. Following electrochemical impedance spectroscopy (EIS) protocols, we\n20 / 67\nfitted the low-frequency region to extract the Warburg coefficient; diffusion coefficients were\nsubsequently calculated using the following equation:\n𝑅2𝑇2\n𝐷 =\n2𝐴2𝑛4𝐹4𝑐2𝜎2\n𝑤\nwhere, D (cm2 s−1) is the diffusion coefficient; R is the gas constant (R = 8.314 J mol−1 K−1); T is the\nabsolute temperature (T = 273.15 K); A (cm2) is the electrode surface area; n is the number of\nelectrons transferred per molecule in the reaction; F is the Faraday constant (F = 96485 C mol−1); c\nis the concentration of ions in the electrode material; σ is the Warburg coefficient, which corresponds\nw\nto the real part of the impedance Z , and its value is is determined by the slope in the plot of w−1/2\nre\nversus Z (Figure R17A).\nre\nFigure R17. (A) The plot of w−1/2 versus Z re . (B) Diffusion coefficient of sodium ions and chloride ions.\nWe also made the corresponding changes in the Piezoionic mechanism of structural and molecular\ndeterminant and Figure 5 of Revised manuscript, as well as Supplementary Fig. 22 to Supplementary\nFig. 27 in Revised Supplementary Information.\nThe Revised Figure 5 as follow:\n21 / 67\nComment 5. Structural Evolution and Crystallinity Correlation: The WAXS/SAXS data (Fig. 2B–E)\nshow increased crystallinity but fail to quantitatively correlate mechanical training with\nnanocrystalline alignment. The 19.5° peak intensity increase could indicate crystallite alignment\nrather than size changes. Azimuthal integration of 2D SAXS patterns would quantify nanofibril\norientation, while Scherrer analysis of crystallite dimensions could link structural evolution to tensile\nproperties. These analyses are essential to substantiate the hierarchical network’s role in\nmechanosensitivity.\nAuthors’ Response: Thank you for your professional questions. We deeply appreciate your expert\nsuggestions. As requested, we have conducted SAXS analyses on the nanocrystalline domains.\n22 / 67\nSAXS was used to characterize the inter-crystal spacing and the average crystal dimension. The\naverage crystal dimension was obtained by the radius of gyration (R ), calculated by applying the\ng\nGuinier equation in the Guinier region:\n𝐼(𝑞) = 𝐼(0)𝑒𝑥𝑝[(−𝑞2𝑅2)⁄3] (3)\n𝑔\n𝑞𝑅 ≪ 1\n𝑔\nwhere I(0) was the zero angle scattering intensity and R was used to represent the size of PVA crystal\ng\nstructure (Figure R18A).\nThe average distance between adjacent crystalline domains L can be estimated from the scattering\nmaxima corresponding to the peak intensity q according to the Bragg expression:\nmax\n𝐿 = 2𝜋⁄𝑞 (1)\n𝑚𝑎𝑥\nwhere scattering vector (q) is defined as:\n𝑞 = 4𝜋sin𝜃⁄𝜆 (2)\nwhere λ is the x-ray wavelength, and 2θ is the scattering angle (Figure R18B).\nIn short, these observations of WAXS and SAXS strongly implies that 20PP–DNE had higher degree\nof crystallinity with smaller nanocrystalline domains. We further analyzed the average size of\ncrystalline domains by fitting SAXS profiles using Guinier equation, which affords a radius of\ngyration (R ) of approximately 7.0 nm, that is, a nanocrystalline dimension (D) of about 7.0 nm\ng\n(Figure R18C). Taken together, these observations allow us to draw conclusions about the\nnanocrystalline morphology: solvent substitution significantly facilitates the nucleation and\nrefinement of nanocrystalline domains reformed in salting-out treatment, and mechanical training\norients hierarchical alignment of nanofibrils and constructs long-range ordered nanocrystals under\nthe confined configurations.\nFigure R18. (A) The modelling of the 1D SAXS profiles of 20PP, 20PP–Na, 20PP–SNE, mechanically trained\n20PP–SNE, and 20PP–DNE. (B) The Lorentz-modified 1D SAXS profiles of 20PP, 20PP–Na, 20PP–SNE,\nmechanically trained 20PP–SNE, and 20PP–DNE. (C) Changes in interdomain spacing (L) and nanocrystalline\ndimension (D) of nanofibrils with progressive manufacturing process, indicating that the orientation of the crystal\nlamellae becomes increasingly perpendicular to the fibrils axis from salting out, solvent substituting, mechanical\ntraining to double-network structure.\n23 / 67\nWe also have reorganized the Mechanical properties and strengthening mechanism of PIEgels and\nFigure 2 in the Revised Manuscript (marked in red color), as well as Supplementary Fig. 11 in\nRevised Supplementary Information.\nThe Revised Figure 2 as follow:\nComment 6. The manuscript presents a potentially valuable contribution by exploring piezoionicity\nin conductive eutectogels. However, significant revisions are necessary to address the major concerns\noutlined above, particularly regarding the mechanistic explanations for piezoionicity and modulus\nenhancement, potential limitations in conductivity, interpretation of structural data, and\ndemonstration of long-term stability. Addressing these points with further experiments, analysis, and\nclarification will substantially strengthen the manuscript and improve its suitability for publication.\nAuthors’ Response: We extend our sincere gratitude for your continued support. We are deeply\n24 / 67\nappreciative of your recognition of our work and your professional suggestions. These comments\nhave significantly enhanced our manuscript's logical framework, mechanistic insights (mechanical,\nelectrical, and piezoionic), and the stability analyses of these properties. As suggested, the revisions\nhave substantially improved the readability of our manuscript.\n25 / 67\n Reviewer #2:\nThis manuscript reports a mechanically trained strategy to fabricate robust piezoionic eutectogels\nwith hierarchical structure, followed by comprehensive characterization and performance evaluation.\nThe proposed eutectogels exhibit piezoionic output while maintaining excellent mechanical\nproperties. However, the manuscript suffers from a lack of rigorous and supported scientific\nexplanation, with complicated/meaningless assertions throughout. Several key concepts and\nmechanisms are insufficiently supported by effective data, which significantly weaken the scientific\ncredibility of this work. Compared to previous reports, the piezoionic performance of the eutectogels\nappears inferior. Given these concerns, the manuscript is not suitable for publication in Nature\nCommunication.\nWe greatly appreciate you for positive, valuable and intriguing comments, which has helped us to\nfurther advance our manuscript. We hope that our point-by-point responses can satisfy your concerns.\nComment 1A. 1. For a scientific paper, it is very necessary to be concise and easy to understand. The\nIntroduction and Results sections contain excessive details, including discussions that are not related\nto the core concept of this manuscript. In addition, the core challenge is not extracted in the\nIntroduction, and the proposal of this work is too far-fetched. This manuscript focuses on the\nstructural design of eutectogel and the evaluation of piezoionic output, so there is no need for\nextensive discussions on biological tissues and PIEZO2 protein in the Introduction.\nAuthors’ Response: Thank you for the professional suggestion. we reorganized the logic of the\nmanuscript and made comprehensive revisions to the entire manuscript.\nWe sincerely appreciate your constructive feedback. The Introduction and Results sections are crucial,\nand we acknowledge that our previous versions were overly verbose and contained unnecessary\ndigressions. In response to your suggestions, we reorganized the logic of the manuscript and made\ncomprehensive revisions to the entire manuscript.\nFirstly, we have rewritten the Introduction and Results, removing extraneous explanations and details\nunrelated to piezoionics. Secondly, within the Introduction, we have explicitly identified the core\nchallenge: Piezoionic materials typically require pressure gradients to generate ionic steaming, yet\nthey often suffer from low mechanical strength. Consequently, achieving compatibility between\nmechanical robustness and piezoionic performance in piezoionic materials represents a fundamental\nchallenge. Finally, we have removed the Introduction of PIEZO2 protein from the Introduction\nsection.\nWe carefully revised the Introduction and Results section and made a thorough modification to it in\nthe Revised Manuscript, and marked in the red.\nComment 1B. In the Discussion section, the authors fully characterized and explained the eutectogels,\n26 / 67\nbut most of the detailed explanations seem to be irrelevant to the core mechanism, and the conclusions\nare too sudden and unconvincing. I strongly suggest the authors to re-edit the manuscript by refining\nthe theoretical framework, strengthening the supporting data, and removing unnecessary descriptions.\nThere is also an excessive amount of self citation.\nAuthors’ Response: We sincerely appreciate your constructive suggestions. Our manuscript was\nindeed not clearly structured. To address this, we have reorganized the logical flow and overall\nframework, and have rewritten the manuscript. The Results section has been restructured into six\nsubsections:\n(1) Molecular and structural design of mechanically robust conductive PIEgels.\n(2) Mechanical properties and strengthening mechanism of PIEgels.\n(3) Electrochemical performances and conductive mechanism of PIEgels.\n(4) Piezoionic performances and piezoionic coefficients of PIEgels.\n(5) Structural and molecular determinant of piezoionic mechanism.\n(6) Continuous piezovoltage and instantaneous response of PIEgels.\nComment 2. The development of eutectogels with piezoionic effects is a key highlight of this study.\nHowever, the term “eutectiogel” here does not seem to be appropriate. Similar to glycerol, acrylic\nacid and acrylamide are common hydrogen bond donors, and their inclusion disrupts the hydrogen\nbond donor-to-acceptor ratio in the system. The authors should critically assess whether the prepared\nsystem qualifies as a deep eutectic solvent. The validity of the eutectogel in this system remains\nuncertain.\nAuthors’ Response: We sincerely appreciate your expert feedback. Regarding whether gels\nfabricated via this protocol qualify as genuine eutectogels, we conducted rigorous experimental\nvalidation through: differential scanning calorimetry (DSC), phase diagram analysis, rheological\nprofiling and Fourier-transform infrared spectroscopy (FTIR). These comprehensive analyses\ncollectively confirm that the resultant polymer gels are eutectogels.\nThe deep eutectic solvent (DES) formation, driven by hydrogen-bond interactions, offers exceptional\ndesign versatility for synthetic tailoring. Synthesis progress the PIEgels as following: 1. Solvent\nexchange: Conversion of hydrogel to eutectogel via aqueous phase replacement with DES. 2.\nMonomer infusion: Immersion in DES precursor solution containing polymerizable monomers. 3.\nNetwork engineering: Construction of double network through UV-initiated radical polymerization.\nTherefore, there is the consideration: Monomers within the DES precursor may act as competitive\nhydrogen-bond acceptors, potentially compromising the integrity of the native DES system. However,\nour systematic validation demonstrates that the mixture formed by incorporating monomers into the\n27 / 67\npristine DES maintains its fundamental DES nature—albeit with potential melting point variations—\nand crucially, the subsequent polymerization process incorporating these monomers into polymeric\nnetworks does not alter the intrinsic hydrogen-bonding regime of DES.\n(1) FT-IR: The DN-E is immersed in water for 24 hours and the hydrogel formed becomes DNH\n(Figure R20A). There is no characteristic peak of glycerol in DNH by FT-IR spectroscopy, which\nindicates that Gly/ChCl is a DES and not a solid state attributed to the substitution of glycerol by\nwater molecules.\n(2) DSC: In order to explore the effect of the melting point of DES, we choose PAAc instead of AAc\nin DES, where the molecular weight of PAAc is selected 2000 and 450000, respectively, to perform\nDSC tests. In comparation with GC (Gly/ChCl) as DES, the addition of AAc significantly reduces\nthe melting point of GCA (Gly/ChCl/AAc) as DES, which may be due to the weakening of hydrogen\nbond interaction due to the destruction of some hydrogen bonds by AAc. However, when PAAc exists\nin DES of GC (Gly/ChCl), the melting point increases significantly. Specifically, the greater the\nmolecular weight of PAAc, the higher the melting point (Figure R24C, D and E). Furthermore, the\nlarger the molecular weight of PAAc, the easier it is to form a gel. In other words, the PAAc-2000\ndid not drastically self-assemble to form a supramolecular gel, whereas the PAAC-450000 formed a\nsupramolecular gel (Figure R2C and D). In particular, DSC tests showed the distinct melting points\nand melting of the PAAc, which indicated a gel state rather than a solid state. The resulting polymeric\nnetworks within the DES matrix undergo supramolecular gelation—manifesting as a temperature-\ntriggered, reversible sol-gel transition (gelation at low temperatures vs. sol formation at elevated\ntemperatures)—demonstrating robust preservation of the DES architecture throughout\npolymerization. Thus, this conclusively establishes PIEgels as authentic eutectogels (Figure R20B\nand R20C).\nBy comparing binary phase diagram of the mixture with various components at room temperature,\nwe found that deep eutectic solvent cannot be formed when α : β is or greater than 1 : 5 (Figure R20D\nand R20E). On the other hand, there is little morphological difference between eutectic solvents\nformed with or without AAc as hydrogen bond donors, but the melting point is significantly lower\n(Figure R20B and R20D). This increase in melting point is due to AAc enhancing the hydrogen bond\ninteraction of DES. These findings suggest that the formation of eutectic solvents is highly dependent\non the composition. Furthermore, DSC tests also show that when the ratio of α : β is greater than or\nequal to 1 : 5, there are obviously two phases in the mixture, and the absorption peak of undissolved\nChCl appears (Figure R11E).\nTherefore, the DES we synthesized is before the eutectic point and is a eutectic solvent, resulting in\nthe eutectogels.\n28 / 67\nFigure R20. (A) FT-IR spectra of 20PP, 20PP–DNE and 20PP–DNH. (B) Various optical photographs, including\nGCA (Gly/ChCl /AAc), GC (Gly/ChCl), GCA2000 (Gly/ChCl /PAAc-2000) and GCA45000 (Gly/ChCl /PAAc-\n450000). (C) Differential Scanning Calorimetry (DSC) tests of GCA, GC, GCA2000 and GCA45000. (D)\nDifferential Scanning Calorimetry (DSC) tests of GA, GAC1, GAC2, GAC3, GAC4, GAC5, GAC6, GAC7, GAC8,\nGAC9, and GAC10. Note: α : β = 1 : 0, 1 : 1, 1 : 2, 1 : 3, 1 : 4, 1 : 5, 1 :6, 1 : 7, 1 : 8, 1 : 9, and 1 : 10. (D) The binary\nphase diagram derived from DSC testing (Gly/AAc = 4 : 1 as α component, and ChCl as β component).\nNotably, this methodology aligns with established eutectogel fabrication strategies in the literature,\nwhere solvent exchange followed by in-situ polymerization has been widely adopted—as exemplified\nby: N. Tang, Y. Jiang, K. Wei, Z. Zheng, H. Zhang, J. Hu, Evolutionary Reinforcement of Polymer\nNetworks: A Stepwise-Enhanced Strategy for Ultrarobust Eutectogels. Adv. Mater. 2024, 36,\n2309576. https://doi.org/10.1002/adma.202309576 (Figure R21).\nFigure R21. Schematic showing the stepwise-enhanced strategy for the construction of ultrarobust PVA eutectogel\nand its evolutionary enhancement process of network structure. Reproduced with permission from ref Adv. Mater.\n2024, 36, 2309576. Copyright 2023 Wiley-VCH GmbH.\nComment 3. While the concept of eutectogel is repeatedly emphasized, the manuscript lacks a clear\nexplanation for its necessity. Furthermore, the authors do not provide explicit reasons for selecting\nspecific materials, such as PEDOT:PSS instead of other conjugated polymers, or choline chloride\n29 / 67\n(ChCl) instead of other quaternary ammonium salts. These choices are crucial for optimizing\npiezoionic performance, yet they are not justified in the manuscript.\nAuthors’ Response: We appreciate your constructive suggestions. The choice of eutectogel and the\ncorresponding components is crucial. Therefore, we have highlighted the advantages of the eutectogel\nby comparison with systems such as hydrogels, organogels, and ionogels. Furthermore, we provide a\ndetailed rationale for the selection of PEDOT:PSS and choline chloride, explaining their specific roles\nand suitability within our study. In summary, the use of eutectogels enables the design of mixed ionic-\nelectronic conductors to achieve piezoionic performance.\n(1) Ionogels/eutectogels achieve high ionic conductivity via mobile ions in ionic liquids/deep eutectic\nsolvents (ILs/DESs), whereas hydrogels/organogels depend on dissolved electrolytes. This inherent\nionic conduction in network is more beneficial for piezoionic materials. Furthermore, eutectogels\nbridge the gap between sustainability (DESs) and functionality (ILs-like properties), enabling the\nbroadly adjustable electronic and electrochemical window. For piezoionics, eutectogels have smaller-\nradius ions, such as chloride ions (Cl−), which are more sensitive to pressure compared to larger-\nmolecular-weight ionic compounds in ionogels (Table R1). Furthermore, DESs, as hydrogen-bonding\nsupramolecular complexes, manipulate the interaction, conformation, and structure of polymer\nnetworks, giving mechanical properties such as self-healing (Angew. Chem. Int. Ed. 2023, 62,\ne202313971), strong and tough and other physical properties such as temperature-resistance (Adv.\nMater. 2024, 36, 2309576).\nThe reported piezovoltage of piezoionic materials are usually transient, meaning that the generated\nvoltage disappears along with the removal of the pressure. PIEgels possesses continuous pressure-\ninduced electrical generation owing to negligible vapor pressure of DES, lasting for over 200 seconds.\nThis requires that the gel itself possess extremely outstanding mechanical properties and\nthermostability to prevent mechanical failure caused by continuous applied pressure (Table R1).\nTable R1. Comparison of the mechanical training of this work with others strong and tough polymer\ngels reported in the literature.\nPolymer gels Solvents Conductivity Hierarchical structure Thermostability Ion species\nHydrogels HO Not intrinsic Cyclic mechanical training Poor No ions\nIonogels Ionic liquids Intrinsic, ionic Cyclic mechanical training Depends on solvent Larger ions\nEutectogels Deep eutectic solvents Intrinsic, ionic Single mechanical training Outstanding Smaller ions\n(2) Furthermore, the selection of PEDOT:PSS and choline chloride (ChCl) likely represents the key\nadvantage underlying the exceptional performance of PIE gels (piezo-ionotronic gels). Deep eutectic\nsolvents (DES), serving as ion-rich solvents, inherently function as typical ionic conductors. However,\ntheir application is constrained by limited conductivity. Consequently, numerous prior studies have\n30 / 67\ndemonstrated that incorporating conductive polymers into ionic conductors constitutes an effective\nstrategy for enhancing electrical performance, namely through ion-exchange facilitated ion-electron\ncoupling. Nevertheless, ion-exchange reactions typically require the introduction of conjugated\nconductive polymers. Extensive research has confirmed that PEDOT:PSS can act as an efficient ionic\ncharge reservoir for ion-exchange reactions, thereby significantly improving the electrical and\nelectrochemical properties of ion-electron mixed conductors. Thus, we selected conventional\nPEDOT:PSS as the conductive polymer (Figure R22).\nOn the other hand, piezoionic devices commonly rely on two ions with high polarity differences to\nachieve selective ion migration, with NaCl being the most frequently employed. To this end, we\nselected choline chloride (ChCl) within the DES as a single anion species. This approach facilitates\na clearer understanding of the piezoionic mechanism.\nFigure R22. The compositional structure of PIEgels comprises the conductive polymer PEDOT:PSS, the ionic\ncomponent NaCl, and the solvent DES. An ion-exchange reaction between PEDOT:PSS and Na+/Cl– is facilitated\nby DES.\nWe also made the corresponding revised in the Introduction and Molecular and structural design of\nmechanically robust conductive PIEgels in Revised Manuscript, and marked in red color, as follow:\n(Line 45) Piezoelectric materials can convert mechanical forces into electrical signals, whereas\npiezoionic materials tend to be based on the movement of ions rather than electrons in response to\npressure gradients. Consequently, piezoionic materials, like electric organs, are regarded as a very\ngood match for biosensings and biointerfaces.\n(Line 59) Obviously, mechanically weak piezoionic mechines, i.e., hydrogels, fail to render the\ncontribution to continuous ionic currents production in response to mechanical forces, along with\nmechanical failure under persistent loading, i.e., crown ether grafted PVA hydrogel as differential\namplifier, zwitterionic hydrogels as piezoionic device with a mobile-ion-free system and piezoionic\nelastomers with ionic plastic crystal.\n(Line 995) We utilized conductive polymer PEDOT:PSS-supported conductivity to construct mixed\n31 / 67\nionic–electronic conductors, i.e., PIEgels, which may provide an accessible pathway for facilitating\npressure-driven ion migrations. The mechanically robust PIEgels are fabricated via mechanical\ntraining, which incorporates deep eutectic solvent (DES) as substituted solvent within semicrystalline\nPVA/PEDOT:PSS hydrogel to conduct mechanical training for building hierarchical structure.\nComment 4A. The authors claim that pre-stretching induces the formation of oriented PVA\nnanocrystals, which serve as channels for directional ion transport. However, the 2DWAXS and\nSAXS results do not exhibit clear crystal orientation, contradicting the data presented in Figure 1D.\nAuthors’ Response: We deeply appreciate your expert suggestions. Although small-angle X-ray\nscattering (SAXS) revealed no significant orientation, cross-sectional scanning electron microscopy\n(SEM) of fractured PIEgels reveals a distinct hierarchical structure. We attribute the absence of SAXS\norientation signatures to the weakening of structural alignment within the double network architecture\nformed during mechanical training. In contrast, trained eutectogels exhibit clear orientation. Thus,\nSEM characterization of PIEgel fractures provides direct evidence of their well-defined hierarchical\norganization (Figure R23).\nFigure R23. Cross-sectional scanning electron microscopy (SEM) of PIEgels.\nWe also made the corresponding changes in the Supplementary Fig. 10 in Revised Supplementary\nInformation.\nComment 4B. Furthermore, the assertion that PVA nanocrystals forms non-porous walls lacks\nsufficient experimental support. Even if such a non-porous and oriented crystalline structure exists,\nthe mechanism by which it facilitates selective ion diffusion remains unexplored, and no reasonable\nexperimental validation is provided as well.\nAuthors’ Response: We appreciate your insightful suggestions. We apologize if this point was not\nsufficiently clarified. While freeze-thawed PVA hydrogels exhibit distinct pores, our subsequent\nsalting-out treatment resulted in a virtually non-porous walls structure. These structural features were\ndirectly visualized by SEM (Figure R24). WAXS and SAXS analyses confirm that salting-out\nenhances the crystallinity of PVA. We wish to clarify that we are not attributing the pore-free structure\ndirectly to the formation of PVA crystalline domains. Rather, we propose that this pore elimination\n32 / 67\narises from a salting-out-induced phase separation process—a mechanism extensively documented\nin prior literature (Nature 590, 594–599 (2021). https://doi.org/10.1038/s41586-021-03212-z).\nFigure R24. The scanning electron microscopy (SEM) images during processing for various gels. (A) Freeze-\nthawed 20PP and (B) Freeze-thaw followed by salting-out 20PP–Na.\nSelective ion diffusion is attributed to the following two aspects:\n(1) Hierarchical network. As highlighted, hierarchical architecture is indeed critical for\npiezoionic performance—an aspect previously unexplored in our work. To address this gap, we\nengineered a non-hierarchical eutectogel and systematically characterized its piezoelectric properties.\nStructurally, the hierarchically nanofibrous network constructed achieve the confinement of pressure-\ndriven ion flux, producing the uniform orientation of ionic migrations. Compared with isotropic three-\ndimensional networks, this structure potentially reduces the spatial energy barrier for ionic migration,\nthereby facilitating ion gradients.\nParticularly, the mechnosensitivity (S) during applying pressure and inactivation time (T) during\nremoving pressure of 20PP–DNE (No trained) respectively shows 651 mV s–1 and 0.116s,\ncorresponding to piezoionic coefficient of 2.6 nV Pa–1 and piezovoltage (∆V) of 7.8 mV. The\nmechnosensitivity (S) during applying pressure and inactivation time (T) during removing pressure\nof 20PP–DNE respectively shows 1457 mV s–1 and 2.569s, corresponding to piezoionic coefficient\nof 9.7 nV Pa–1 and piezovoltage (∆V) of 30 mV. Therefore, 20PP–DNE exhibit a 3.6-fold increase\nin ∆V, a 3.5-fold enhancement in piezoionic coefficient, and a 2.2-fold improvement in S. However,\nthey require a 22-fold longer T. These findings indicate that the hierarchical architecture facilitates\ngreater ion migration, producing the remarkable inactivation kinetics (Figure R25).\n(2) Charge compensation mechanism. To investigate charge separation mechanisms, we engineered\nNaCl-free eutectogels containing exclusively chloride ions (sourced from the choline chloride\ncomponent of the deep eutectic solvent) and PEDOT:PSS-free eutectogels containing only NaCl. We\nanticipated substantially degraded piezoionic performances in NaCl-free and PEDOT:PSS-free\neutectogels due to the absence of ion-electron coupling charge compensation between Na+/Cl− and\nPEDOT:PSS.\nWe conducted comparative experiments that revealed significantly inferior piezoionic performances\nin eutectogels containing either NaCl or PEDOT:PSS alone, compared to the integrated PIEgels.\nNotably, NaCl-free eutectogels exhibit dramatically shortened the T, with a 49-fold reduction\ncompared to PIEgels. These compelling evidences establish the pivotal role of ion-electron coupling\nin governing remarkable piezoionic activation and inactivation kinetics, contributing to outstanding,\ncontinuous piezoionic output (Fig. R26).\n33 / 67\nFigure R25. The influence of hierarchical structure on the piezoionic performances. (A and B) The piezovoltage\noutput by continuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and\nion inactivation kinetics (B) for trained 20PP–DNE. (C and D) The piezovoltage output by continuously applying\nstep force stimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for\nuntrained 20PP–DNE. (E and F) Comparison of piezoionic performances between trained and untrained 20PP–\nDNE. (E) Piezovoltage and piezoionic coefficient. (F) mechanosensitivity and inactivation time.\n34 / 67\nFigure R25. The influence of hierarchical structure on the piezoionic performances. (A and B) The piezovoltage\noutput by continuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and\nion inactivation kinetics (B) for 20PP–DNE. (C and D) The piezovoltage output by continuously applying step\nforce stimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for 0PP–\nDNE. (E and F) The piezovoltage output by continuously applying step force stimulation (E) and corresponding\npiezoionic ion diffusion kinetics and ion inactivation kinetics (F) for NaCl-free 20PP–DNE. (G and H) Comparison\n35 / 67\nof piezoionic performances between 20PP–DNE (PP/NaCl), 0PP–DNE (No PP), and NaCl-free 20PP–DNE (No\nNaCl). (G) Piezovoltage and piezoionic coefficient. (H) mechanosensitivity and inactivation time.\nWe also made the corresponding revised in the Mechanical properties and strengthening mechanism\nof PIEgels and Structural and molecular determinant of piezoionic mechanism, as well as Figure 2\nand Figure 5 in Revised Manuscript, and marked in red color. We also made the corresponding\nchanges in the Supplementary Fig. 22 and Supplementary Fig. 24 in Revised Supplementary\nInformation.\nThe Revised Figure 2 as follow:\nThe Revised Figure 5 as follow:\n36 / 67\nComment 5A. The study presents an insufficient range of PEDOT:PSS ratios, making it difficult to\nderive a meaningful correlation between PEDOT:PSS content, mechanical properties, and piezoionic\nperformance.\nAuthors’ Response: We sincerely appreciate your insightful suggestion. Given that PEDOT:PSS\nserves as the major component of PIEgels, its critical roles in mechanical and piezoelectric properties\nwere unfortunately overlooked in our initial analysis. In summary, while the mechanical properties\nscale linearly with PEDOT:PSS content, the electrochemical and piezoelectric performance is\ngoverned by ion-exchange reaction kinetics—consistent with the predominantly ionic conductive\nnature of PIEgels.\n37 / 67\n(1) Mechanical properties. A marked enhancement in the mechanical properties of double network\neutectogels was observed with increasing PEDOT:PSS content. This indicates that the bonding\ninteractions between PVA and PSS chains were further strengthened during double network formation,\nresulting in reinforced mechanical performance. The double network architecture was constructed by\npre-immersing single-network eutectogels in DES precursor solution. This immersion process\npresumably facilitated additional crystallization of PVA and its enhanced bonding with PSS, thereby\ncontributing to the significant mechanical improvement. These structural transitions occur at multiple\nlength scales including hierarchically interpenetrated networks, hierarchical nanofibrils and\nnanocrystalline domains, and intermolecular interactions resulting in energy dissipation\nmultimechanisms from molecular to mesoscopic scales, and contributing to the improved mechanical\nperformance of DNE, in terms of strength, stretchability and toughness (Figure R27).\nFigure R27. (A and B) Typical stress‒strain curves under tension (A) and summarized average results of Young’s\nmoduli, fracture strengths and work of fracture (B) for 0PP–DNE, 10PP–DNE and 20PP–DNE. (I) 2D WAXS\npatterns, 2D SAXS patterns and SEM image of 20PP–DNE. (C) Schematic illustration of the energy dissipation\nmultimechanisms from molecular to mesoscopic scales.\n(2) Piezoionic performances. Contrary to the monotonic trend in mechanical properties, the\npiezoionic performances of PIEgels does not increase with higher PEDOT:PSS loading. Instead,\n10PP–DNE exhibits a reduction compared to 0PP–DNE, followed by a substantial enhancement in\n20PP–DNE. This trend aligns precisely with the conductivity evolution. We attribute the non-\nmonotonic behavior to ion transport kinetics: insufficient PEDOT:PSS content (10 wt%) induces\ncharge-blocking effects, disrupting efficient charge compensation via ion-exchange between\n38 / 67\nPEDOT:PSS and Na+/Cl− (Figure R28).\nFigure R28. (A) Piezovoltage (∆V) and piezoionic coefficient for 0PP–DNE, 10PP–DNE and 20PP–DNE. (B)\nmechnosensitivity (S) and inactivation time (T) for 0PP–DNE, 10PP–DNE and 20PP–DNE. (C) The molecular\norigins of piezoionicity in conductive, hierarchical PIEgels for applying pressure (top) and removing pressure\n(bottom). Na+ ions and Cl– ions are the charge-compensating species of PEDOT:PSS, achieving dynamic\nmodulation of piezoionic activation/inactivation kinetics via pressure-responsive switching.\nWe also made the corresponding revised in the Mechanical properties and strengthening mechanism\nof PIEgels and Piezoionic performances and piezoionic coefficients of PIEgels, as well as Figure 2\nand Figure 4 in Revised Manuscript, and marked in red color. We also made the corresponding\nchanges in the Supplementary Fig. 19 in Revised Supplementary Information.\nComment 5B. Moreover, the bonding interactions between PEDOT:PSS and PVA during the freeze-\nthaw and photocuring processes remain unclear, despite being a crucial aspect of the material system.\nThe authors should provide a more systematic investigation into these factors.\nAuthors’ Response: We deeply appreciate your expert and constructive feedback. Investigating the\nbonding interactions between PEDOT:PSS and PVA is indeed essential for elucidating both\nmechanical reinforcement mechanisms and piezoionic mechanisms. To address this, we have\nconducted a comprehensive multiscale analysis: density functional theory (DFT) calculations,\nindependent gradient model (IGMH) visualization and FTIR spectroscopy.\nDFT calculations reveal a critical bonding hierarchy: The PSS‒PVA interaction exhibits a binding\nenergy (‒135.5 kJ mol‒1) second only to the PEDOT‒PSS bonding (‒173.6 kJ mol‒1), and\napproximately twice that of PVA‒PEDOT (‒63.9 kJ mol‒1). This pronounced energy differential\nestablishes PSS as a preferential interfacial intermediary, bridging PVA chains and PEDOT\nbackbones to form pressure-responsive hierarchal networks (Figure R29A and R29B).\nFor IGMH map, the redder (bluer) the color, the larger (smaller) the contribution of the atom to the\ninteractions (Angew. Chem. Int. Ed. 2025, e202504895. https://doi.org/10.1002/anie.202504895).\nIGMH analysis reveals distinct interfacial bonding regimes: While the binding of PVA‒PEDOT is\nprimarily governed by hydrogen bonding and van der Waals interactions, PSS‒PVA exhibit\nsubstantially stronger bonding characteristics indicative of chemical bonding-consistent with prior\nreports (Figure R29C) (Adv. Mater. 2024, 36, 2304145. https://doi.org/10.1002/adma.202304145).\nSpecifically, sulfonate groups (‒SO ⁻) on PSS form chemical bonds with hydroxyl groups (‒OH) on\nsulfonate S=O stretching vibration emerges with increasing PEDOT:PSS content, demonstrating\nexceptionally strong sulfonate-hydroxyl interactions approaching covalent bond strength (Figure\nR29D).\nFigure R29. (A) Comparison of interaction energy between conductive polymer PEDOT:PSS and polymer PVA by\nDFT optimizations. (B) Structure of PEDOT–PSS, PEDOT–PVA and PSS–PVA btained DFT optimizations. (C)\nIGMH map showing intermolecular interactions of PVA–PEDOT and PVA–PSS, each molecule is defined as a\nfragment in the IGMH analysis. The coloring range is −0.05 to 0.05 a.u. The color bar indicates the sign(λ )ρ values,\n2\nwith blue representing prominent attractive interactions, red indicating prominent repulsive interactions in the\nregions with steric effect, and green exhibiting very weak interactions. (D) FTIR spectra of 20PP–DNH, 20PP–\n40 / 67\nDNE and 20PP.\nWe made the corresponding changes in the Supplementary Fig. 5, Fig. 26 and Fig. 27 in Revised\nSupplementary Information. We also made the corresponding revised in the Mechanical properties\nand strengthening mechanism of PIEgels and Structural and molecular determinant of piezoionic\nmechanism and Figure 5 in Revised Manuscript, and marked in red color, as follow:\n(Line 164) This is attributed to chemical bonding in the SO − group of PEDOT:PSS and the –OH of\n(Supplementary Note 1).\n(Line 192) This immersion process presumably facilitated the enhanced bonding between PVA and\nPSS, thereby contributing to the significant mechanical improvement.\n(Line 368) Furthermore, the PSS‒PVA interaction exhibits a binding energy (‒135.5 kJ mol‒1) second\nonly to the PEDOT‒PSS bonding (‒173.6 kJ mol‒1), and approximately twice that of PVA‒PEDOT\n(‒63.9 kJ mol‒1). This pronounced energy differential establishes PSS as a preferential interfacial\nintermediary, bridging PVA chains and PEDOT backbones to form pressure-responsive hierarchal\nnetworks (Fig. 5D to 5F, Supplementary Fig. 25 to Supplementary Fig. 27).\nComment 6A. The manuscript states that “PEDOT:PSS has an effect on for differential ion flows,\nwith a positive or negative correlation depending on the content, which has been confirmed by\nconductivity and electrochemcial” and “we primarily attributed the piezoionic behavior to the\npresence of conducive polymer in PIEgel”. However, those claims are not adequately supported by\nexperimental data.\nAuthors’ Response: We sincerely appreciate you for valuable feedback. The “PEDOT:PSS has an\neffect on for differential ion flows, with a positive or negative correlation depending on the content,\nwhich has been confirmed by conductivity and electrochemcial” is used because we found that the\nelectrical conductivity and piezoionic properties exhibited similar trends with varying PEDOT:PSS\nconcentrations. Specifically, both properties were lower at 10% PEDOT:PSS than those at 0% and\n20% concentrations. This refinement was made because our initial description may have been\nimprecise: (Line 304) These experimental findings confirms that 20 wt% PEDOT:PSS substantially\npromotes the piezoionic ion diffusion kinetics in applying pressure, accompanied by outstanding ion\ninactivation kinetics after removing pressure, whereas 10 wt% hinders ion diffusion kinetics, in\ncomparison to PIEgels without PEDOT:PSS. This correlation further confirms that PEDOT:PSS is\ncapable of altering ionic conduction via ion-exchange reaction, which is dependent on the\nconcentration (Supplementary Fig. 19). Furthermore, the variation trend of piezoionic performance\nwith the PEDOT:PSS concentration is consistent with the electrochemical properties.\n41 / 67\nTo further validate piezoionic behavior, we conducted an in-depth investigation of the piezoionic\nmechanism via controlled experiments and density functional theory (DFT) calculations.\n1. DFT calculations. To elucidate the ion-electron coupling effect, we performed DFT calculations\nthat revealed strong bonding interactions between PEDOT and Cl− (‒142.7 kJ mol‒1), as well as\nbetween PSS and Na+ (‒309.1 kJ mol‒1). In contrast, the bonding energies of PEDOT‒Na and PSS‒\nCl are only as low as ‒36.4 kJ mol‒1 and ‒37.9 kJ mol‒1, respectively. These computational results\ndemonstrate the existence of a robust charge compensation mechanism via the ion exchange reaction\nbetween Na+/Cl– and PEDOT:PSS (Figure R30).\n2. Ion-electron Coupling. To investigate charge separation mechanisms, we engineered a NaCl-free\neutectogel containing exclusively chloride ions (sourced from the choline chloride component of the\ndeep eutectic solvent). We anticipated substantially degraded piezoionic performances in NaCl-free\neutectogel due to the absence of sodium-mediated charge compensation between Na+ and PSS in\nPEDOT:PSS. Furthermore, the 0PP–DNE control group (containing only NaCl without PEDOT:PSS)\nexhibits a drastic deterioration in piezoionic performances (Figure R31A, R31B and R31C). These\nfindings conclusively demonstrate that the synergistic coupling between PEDOT:PSS and Na+/Cl− is\nessential for enhanced piezoionic performances.\nCollectively, these controlled experiments provide definitive validation of the DFT-predicted ion-\nelectron coupling-mediated charge compensation mechanism between PEDOT:PSS and Na+/Cl−,\nestablishing a robust experimental-theoretical framework for piezoionic mechanism.\n42 / 67\nFigure R30. (A) Electrostatic potential distribution of PEDOT and PSS obtained by density functional theory (DFT)\noptimizations. (B) Comparison of interaction energy between conductive polymer PEDOT:PSS and ionic\ncomponents Na/Cl by DFT optimizations. (C) Structure of PEDOT–Cl, PEDOT–Na, PSS–Cl and PSS–Na obtained\nDFT optimizations.\nWe also made the corresponding revised in the Piezoionic performances and piezoionic coefficients\nof PIEgels and Structural and molecular determinant of piezoionic mechanism and Figure 5 in\nRevised Manuscript, and marked in red color.\nComment 6B. Additionally, it is unclear whether the electronic conductivity of PEDOT:PSS\ninfluences piezoionic performance. Further investigation and clarification are necessary.\nAuthors’ Response: We sincerely appreciate you for valuable feedback. Contrary to the monotonic\ntrend in mechanical properties, the piezoionic performances of PIEgels does not increase with higher\nPEDOT:PSS loading.\n43 / 67\nFigure R31. (A to C) Ion-electron coupling validation: (A) Electronic conductivity (𝜎 ) and ionic conductivity (𝜎)\n𝑒 𝑖\nfor 0PP–DNE (No PEDOT:PSS), NaCl-free 20PP–DNE (No NaCl), and 20PP–DNE (PEDOT:PSS + NaCl). (B)\nPiezovoltage (∆V) and piezoionic coefficient for 0PP–DNE (No PEDOT:PSS), NaCl-free 20PP–DNE (No NaCl),\nand 20PP–DNE (PEDOT:PSS + NaCl). (C) mechnosensitivity (S) and inactivation time (T) for 0PP–DNE (No\nPEDOT:PSS), NaCl-free 20PP–DNE (No NaCl), and 20PP–DNE (PEDOT:PSS + NaCl). (D to E) Conductivity-\nPiezionics correlation. (D) Electronic conductivity (𝜎 ) and ionic conductivity (𝜎) for 0PP–DNE, 10PP–DNE and\n𝑒 𝑖\n20PP–DNE. (E) Piezovoltage (∆V) and piezoionic coefficient for 0PP–DNE, 10PP–DNE and 20PP–DNE. (F)\nmechnosensitivity (S) and inactivation time (T) for 0PP–DNE, 10PP–DNE and 20PP–DNE.\nParticularly, the mechnosensitivity (S) during applying pressure and inactivation time (T) during\nremoving pressure of 20PP–DNE respectively shows 1457 mV s–1 and 2.569s, corresponding to\npiezoionic coefficient of 9.7 nV Pa–1 and piezovoltage (∆V) of 30 mV. The S and T of 10PP–DNE\nrespectively is 9.8 mV s–1 and 0.841s, corresponding to piezoionic coefficient of 1.9 nV Pa–1 and ∆V\nof 5.8 mV. Whereas the S and T of 0PP–DNE respectively is 900 mV s–1 and 0.485s, corresponding\nto piezoionic coefficient of 2.6 nV Pa–1 and ∆ V of 7.9 mV (Figure R31E and R31F). These\nexperimental findings confirm that 20 wt% PEDOT:PSS substantially promotes the piezoionic ion\ndiffusion kinetics in applying pressure, accompanied by outstanding ion inactivation kinetics after\nremoving pressure, whereas 10 wt% hinders ion diffusion kinetics, in comparison to PIEgels without\nPEDOT:PSS. This correlation further confirms that PEDOT:PSS is capable of altering ionic\nconduction via ion-exchange reaction, which is dependent on the concentration.\nIn short, 10PP–DNE exhibits a reduction compared to 0PP–DNE, followed by a substantial\nenhancement in 20PP–DNE. This trend aligns precisely with the conductivity evolution. We attribute\nthe non-monotonic behavior to ion transport kinetics: insufficient PEDOT:PSS content (10 wt%)\ninduces charge-blocking effects, disrupting efficient charge compensation via ion-exchange between\nPEDOT:PSS and Na+/Cl− (Figure R31D).\nWe reorganized the piezoionic mechanism in the Piezoionic performances and piezoionic coefficients\nof PIEgels and Structural and molecular determinant of piezoionic mechanism and Figure 5 in\nRevised Manuscript, and marked in red color.\nComment 7. The authors rely on SEM images to analyze the phase separation, crystallinity,\nmolecular chain network changes, and even bonding within the eutectogels. These imprecise analyses\nlead to low credibility of the relevant conclusions. In the infrared spectroscopy analysis, no in-situ\nFTIR data is provided, making statements such as \"during the self-assembly process\" inappropriate.\nMoreover, the use of 2D correlation spectroscopy (2DCOS) to analyze infrared spectra under\ntemperature fluctuations is unrelated to piezoionic performance under pressure. The authors should\nprovide a more precise and relevant spectroscopic analysis.\nAuthors’ Response: We appreciate your insightful suggestions. We sincerely apologize for the\nmisunderstanding caused by the poor logic of the manuscript. The reinforced mechanical properties\nof PIEgels are derived from the energy dissipation multimechanisms from molecular to mesoscopic\nscales. Therefore, SEM is used to analyze the network structure at the micrometer scale, WAXS and\nSAXS are used to analyze the nanocrystalline domains and PVA crystallinity at the nanometer scale,\nand FTIR and in-situ FTIR are used to analyze the bonding interactions at the molecular scale.\n2DCOS is not used for analyzing piezoionic properties, but to analyze the mechanical reinforcement\nmechanisms at the molecular scale.\nBuilding on these insights, we employed Raman spectroscopy and X-ray photoelectron spectroscopy\n(XPS) to directly validate the piezoionic mechanism.\nWe reorganized the Mechanical properties and strengthening mechanism of PIEgels and Figure 2 in\nRevised Manuscript. The Revised Figure 2 as following:\n45 / 67\nComment 8A. The methodology for piezoionic testing is unclear. According to Figures 4a and 4b, it\nis difficult to establish a pressure gradient between the two electrodes, raising concerns about the\nsource of the anion-cation diffusion difference. Additionally, the applied pressure reaches the MPa\nrange, while the corresponding force is only in the N range, necessitating further clarification of the\nexperimental setup.\nAuthors’ Response: We sincerely appreciate your valuable comments. We have revised this\nambiguous description, which likely originated from the omission of specimen dimensions. For\nclarity: During piezoionic performances coefficients characterization, a pressure of 3 MPa was\nuniformly applied, corresponding to ~ 300 N force on specimens (1 cm² contact area, 1 cm × 1 cm ×\n1.5 mm). In long-term stability tests, 2 MPa pressure was maintained, equating to ~ 150 N force on\nspecimens (0.75 cm² contact area, 0.85 cm × 0.85 cm × 1.5 mm). Figure R31 shows the schematic of\nthe piezoionic measurement system. This device is composed of the force sensor (Simbatough,\nSBT291) and the linear motors (LinMot, BF01-37).\nFigure R32. Schematic illustration of the piezoionic measurement setup.\nWe have made significant revisions to the PIEgels size in Revised Manuscript.\nComment 8B. The observed baseline is unstable, which further weakens the reliability of the results.\nTo prove the stability, I strongly recommend the authors to conduct test at least 1000 cycles.\nAuthors’ Response: We appreciate your insightful suggestions. Regarding baseline instability, we\nprovide the following clarification: To exclude interference from pre-existing charges on\npiezoelectric output, a preconditioning step was implemented for 20PP–DNE specimens. Specifically,\npre-loading pressure was applied to induce initial charging prior to formal testing. Results confirm\nthat piezoelectric voltage generation remains uncompromised by stored charges, demonstrating\ncontinuous pressure-driven electromechanical coupling. However, under pre-charged conditions,\ncontinuous piezoelectric output gradually shifts the baseline toward the intrinsic zero-potential state\nthrough charge dissipation dynamics.\n1000 cycles. Mechanical stability testing revealed that the PIEgels retains considerable stability over\n1000 compression cycles. The hysteresis commences a steady-state phase after the second cycle,\nexhibiting only a gradual decline. Under continuous 3 Hz cyclic compression at 2 MPa stress, the\npiezovoltage output maintained stable operation for 220 seconds before undergoing significant\nattenuation. Beyond this duration, the output voltage decayed to 50% of its peak piezovoltage\namplitude, with the system enduring > 700 compressive cycles while preserving pressure-induced\npiezovoltage output (Figure R33). In short, the piezoionic performances demonstrates endurance\nthrough 700 continuous electromechanical cycles. This significantly exceeds the durability currently\nreported for state-of-the-art piezoionic gel materials (Science 2022, 376, 502-507. DOI:\n10.1126/science.aaw1974; Angew. Chem. Int. Ed. 2025, 64, e202415000.\nhttps://doi.org/10.1002/anie.202415000).\nFigure R33. (A) Piezovoltage response stability of individual PIEgels under successive step acting force with\nsinusoidal perturbations. (B) Typical force‒time curves under repeated step compressions at a pressure of ~ 2.0\nMPa. PIEgels size: 0.7 cm × 0.7 cm × 1.5 mm. (C) Stress‒strain curves of 1000 consecutive compression -relaxation\ncycles for 20PP–DNE at strain of 50% (D) related hysteresis values. The curves are horizontally shifted for clarity.\nWe also made the corresponding changes in the Continuous piezovoltage and instantaneous response\nof PIEgels and Figure 6 in the Revised Manuscript, as well as Supplementary Fig. 17 and Fig. 30 in\nRevised Supplementary Information.\nComment 9. The conductivity of reported eutectogel (~29 S cm⁻¹) is extraordinarily high, surpassing\n47 / 67\nmany inorganic materials. The authors should provide detailed explanations regarding the\nmeasurement and calculation methods to justify this exceptional value. Additionally, the measured\nresistance values appear to be inconsistent with the reported current densities. More comprehensive\ntesting and validation are required.\nAuthors’ Response: We appreciate your insightful suggestions, which rightly identified the\npreviously underexplored electrochemical mechanisms. The observed discrepancy between\nimpedance and current density is well-documented in literature. This divergence primarily stems from\nfundamental methodological differences: current density is measured under direct current (DC)\nconditions probing steady-state behavior, whereas electrochemical impedance spectroscopy (EIS)\noperates under alternating current (AC) excitation characterizing dynamic processes across\nfrequencies.\n(1) Measurement and calculation methods. We fabricated a series of coin batteries assembled by\nPIEgels electrolyte and Zn anode/cathode for electrochemical measurements. In ion-electron mixed\nPIEgels, electronic and ionic charge carriers do not display the same polarization phenomena, neither\nthe same transport kinetics. EIS allows identifying the contributions of those two charge carriers to\nthe electrical conductivity using established equivalent circuit analysis, involving electronic\nconduction pathway and ionic conduction pathway. EIS plots show two semicircles: one depressed\nsemicircle at lower frequency and a segment of a greater semicircle within the higher frequency\nregion, which indicates two kinds of conduction, respectively, electronic and ionic. In the analysis of\nionic conduction, we used the Randle equivalent circuit, with R representing ionic resistance and C\ni dl\nrepresenting double-layer capacitance. Parallel to the double-layer capacitance, we considered the\ndiffusion impedance due to the faradaic reaction, consisting of the charge transfer resistance R and\nct\nthe Warburg impedance Z . The electronic conducting component was represented by pure resistance,\nw\nR . We treated ionic conductivity and electronic conductivity as independent, leading to R and R\ne e i\narranged in parallel. Electronic and ionic conductivities are calculated using the expression:\n𝜎 = 𝐿⁄(𝑆𝑅)\nwhere L represents the electrode distance, S is the cross-sectional area of the sample, and R is the\nresistance extracted from the equivalent circuit fitting. Gamry Echem Analyst software (version 6.3)\nwas used for fitting the circuit models to the impedance data. The total conductivity is calculated\nusing the expression:\n𝜎 = 𝜎 +𝜎\n𝑒 𝑖\n48 / 67\nFigure R34. A comparison of 0PP–DNE, 20PP–DNE and 20PP–DNE without NaCl in terms of (A) ionic\nconductivity and electronic conductivity, as well as (B) the total conductivity. 20PP–DNE exhibits the remarkable\nconductivity owing to the outstanding ion-electron coupling effect. Data were presented as mean ± SD (n = 3\nindependent samples).\nFigure R35. (A) The evolution process of ionic conductivity (σ) and electrical conductivity (σ ) determined from\ni e\nthe impedance spectra by equivalent circuit fitting analysis. (B) Schematic illustration of conductive mechanism of\n49 / 67\nPIEgels and the ion exchange reaction between PEDOT:PSS and Na+/Cl− in PIEgels.\n(2) Enhanced conductivity. In order to accurately verify the ion-electron coupling, we implemented\na comprehensive validation strategy integrating experimental characterization for the evolution\nprocess of conductivity and DFT optimization. Through systematic comparative experiments, we\nmapped the evolution of ionic and electronic conductivities as functions of PEDOT:PSS content and\nsolvent composition, conclusively demonstrating the ion-electron coupling effect (Figure R34).\nComplementarily, DFT-optimized structures revealed a substantial negative Gibbs free energy\nchange (ΔG = −317.7 kJ/mol) for the ion-exchange reaction between PEDOT:PSS and Na+/Cl−,\nconfirming its thermodynamic spontaneity and highlighting its critical role in enhancing piezoionic\nperformances (Figure R35).\nWe have made significant revisions to the Electrochemical performances and conductive mechanism\nof PIEgels and Figure 3 in the Revised Manuscript. The Revised Figure 3 as following:\n50 / 67\nComment 10. The manuscript describes a conductive device based on a series configuration.\nHowever, this structure does not seem to be suitable for piezoionic applications. Further explanation\nis needed to justify the device design. In addition, the demonstration of this device in the manuscript\nis not related to biosensors, and therefore cannot support the bioelectronic application mentioned by\nthe authors.\nAuthors’ Response: We appreciate your reminder and apologize for our presentation. We deeply\nappreciate your invaluable suggestions, which provide critical guidance for advancing the practical\ndeployment of PIEgels, governing real-world applications in energy-autonomous systems using\nPIEgels. Following your insightful suggestions, we systematically evaluated their stability in ionic\nenvironments through controlled immersion experiments. Specifically, PIEgels were immersed for\n24 hours in: (i) 2M NaCl aqueous solution and (ii) pure water, inducing transformation into hydrogel\n(named as NaCl–24H and H\nPIEgel performance in ion-rich physiological environments, precluding their use as implantable\nbiosensors (Figure R36).\nHowever, cascaded PIEgel architectures exhibit exceptional efficacy in non-implantable domains:\nMotion Monitoring and Mechanical Energy Harvesting. In accordance with the identified\nperformance boundaries, the Revised Manuscript has systematically eliminated claims regarding bio-\nimplantation potential, i.e., Biosensor and Flexible Bioelectronics.\nFigure R36. The influence of ionic environments on the piezoionic stability. (A and B) The piezovoltage output by\ncontinuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and ion\ninactivation kinetics (B) for NaCl–24H. (C and D) The piezovoltage output by continuously applying step force\n51 / 67\nstimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for H O–24H.\nPIEgels, Discussion, and Revised Figure 6 in the Revised Manuscript.\nComment 11. The manuscript contains numerous confusing terms, such as \"piezoionicity-induced\nmechanotransduction\", \"piezoionic diffusion\", \"electromechanical coupling\", \"hysteretic\nintermediate\", \"piezoionicity-induced mechanotransduction\". Overall, readability is low, with certain\nsections having contradictory statements. The manuscript should be thoroughly revised, and\nprofessional language editing is strongly recommended.\nAuthors’ Response: We appreciate your insightful suggestions and apologize for our presentation.\nThe manuscript has been comprehensively revised to rigorously refine the terminology. We now\nexclusively employ two scientifically precise descriptors: (1) Pressure-driven ion migration; (2)\nPressure-induced piezovoltage output. Furthermore, the entire manuscript has undergone\ncomprehensive professional language editing by an engaged team of specialists.\n52 / 67\n Reviewer #3:\nIn this manuscript, a double crosslinked network of piezoionic eutectogels (PIEgels) with hierarchical\nnanofiber networks is designed to solve the problem of voltage decay of conventional piezoelectric\nmaterials under long-term pressure by enhancing the mechanical properties of the materials and\noptimizing the ion transport paths. Earlier studies by Madden group and Derek Ho group\ndemonstrated piezoionic hydrogels capable of achieving mechanoelectrical coupling via pressure-\ndriven ion flux. Notably, these hydrogels with high mechanical sensitivity are intrinsically required\nto produce substantial piezoionic output, yet they are mechanically soft.This work demonstrates that\nrational molecular and structural design enables the realization of piezoionic effects in mechanically\nrobust gels, while maintaining exceptional piezoionic output performance. Overall, this study\ninnovatively combines mechanical robustness with piezoionicity, a breakthrough likely to attract\nsignificant interest in related fields. The comments and suggestions are as follows:\nWe greatly appreciate your meticulous review and intriguing comments, which has helped us to\nfurther improve our manuscript and research value. We hope that our point-by-point responses can\nsatisfy your concerns.\nComment 1A. Mechanistically, the superior piezoionic output of PIE gels arises from their\nhierarchical architecture and charge compensation mechanism. The hierarchical structure restricts the\ndirection of ion flow, so could this phenomenon be demonstrated by in situ characterization\ntechniques or molecular dynamics simulations to visualize the migration path of ions more intuitively?\nAuthors’ Response: Thank you for your insightful comment on this aspect and we completely agree,\nand thank you for reminding us. We acknowledge that while the critical role of hierarchical structures\nwas emphasized, direct evidence from molecular dynamics (MD) simulations proved unattainable\ndespite extensive efforts. The inherent challenge lies in the non-spontaneous nature of hierarchical\nstructures, which require explicit maintenance during modeling—precluding successful MD\nvisualization. We sincerely regret this limitation. The non-spontaneous emergence of hierarchical\nstructures in molecular dynamics simulations necessitates manual intervention, which is a potential\nsource of model failure.\nNevertheless, rigorous control experiments provide robust validation for both the hierarchical\norientation and the charge compensation mechanism. As highlighted, hierarchical architecture is\nindeed critical for piezoionic performance—an aspect previously unexplored in our work. To address\nthis gap, we engineered a non-hierarchical eutectogel and systematically characterized its\npiezoelectric properties. Structurally, the hierarchically nanofibrous network constructed achieve the\nconfinement of pressure-driven ion flux, producing the uniform orientation of ionic migrations.\nCompared with isotropic three-dimensional networks, this structure potentially reduces the spatial\nenergy barrier for ionic migration, thereby facilitating ion gradients.\n53 / 67\nParticularly, the mechnosensitivity (S) during applying pressure and inactivation time (T) during\nremoving pressure of 20PP–DNE (No trained) respectively shows 651 mV s–1 and 0.116s,\ncorresponding to piezoionic coefficient of 2.6 nV Pa–1 and piezovoltage (∆V) of 7.8 mV. The\nmechnosensitivity (S) during applying pressure and inactivation time (T) during removing pressure\nof 20PP–DNE respectively shows 1457 mV s–1 and 2.569s, corresponding to piezoionic coefficient\nof 9.7 nV Pa–1 and piezovoltage (∆V) of 30 mV. Therefore, 20PP–DNE exhibit a 3.6-fold increase in\n∆V, a 3.5-fold enhancement in piezoionic coefficient, and a 2.2-fold improvement in S. However,\nthey require a 22-fold longer T. These findings indicate that the hierarchical architecture facilitates\ngreater ion migration, producing the remarkable inactivation kinetics (Figure R37 and Figure R38).\nFigure R37. The influence of hierarchical structure on the piezoionic performances. (A and B) The piezovoltage\noutput by continuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and\nion inactivation kinetics (B) for trained 20PP–DNE. (C and D) The piezovoltage output by continuously applying\nstep force stimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for\nuntrained 20PP–DNE.\n54 / 67\nFigure R38. Comparison of piezoionic performances between trained and untrained 20PP–DNE. (A) Piezovoltage\nand piezoionic coefficient. (B) mechanosensitivity and inactivation time.\nComment 1B. In addition, the molecular-scale charge compensation mechanism, which may be a\nnovel concept to this study, demands further elucidation.\n(1) Charge compensation. To elucidate the ion-electron coupling effect, we performed DFT\ncalculations that revealed strong bonding interactions between PEDOT and Cl− (‒142.7 kJ mol‒1), as\nwell as between PSS and Na+ (‒309.1 kJ mol‒1). In contrast, the bonding energies of PEDOT‒Na and\nPSS‒Cl are only as low as ‒36.4 kJ mol‒1 and ‒37.9 kJ mol‒1, respectively. These computational\nresults demonstrate the existence of a robust charge compensation mechanism via the ion exchange\nreaction between Na+/Cl– and PEDOT:PSS (Figure R39). More importantly, as the charge-\ncompensating species for PEDOT, Cl⁻ preferentially attacks the C+ site rather than the S+ site, thereby\ntriggering the propagation of the electron transport.\nFigure R39. (A) Electrostatic potential distribution of PEDOT and PSS obtained by density functional theory (DFT)\noptimizations. (B) Comparison of interaction energy between conductive polymer PEDOT:PSS and ionic\ncomponents Na/Cl by DFT optimizations. (C) Structure of PEDOT–Cl, PEDOT–Na, PSS–Cl and PSS–Na obtained\nDFT optimizations.\n(2) The binding of PEDOT:PSS and PVA. DFT calculations reveal a critical bonding hierarchy:\nThe PSS‒PVA interaction exhibits a binding energy (‒135.5 kJ mol‒1) second only to the PEDOT‒\nPSS bonding (‒173.6 kJ mol‒1), and approximately twice that of PVA‒PEDOT (‒63.9 kJ mol‒1). This\npronounced energy differential establishes PSS as a preferential interfacial intermediary, bridging\nPVA chains and PEDOT backbones to form pressure-responsive hierarchal networks (Figure R40A\n55 / 67\nand R40B).\nFor IGMH map, the redder (bluer) the color, the larger (smaller) the contribution of the atom to the\ninteractions (Angew. Chem. Int. Ed. 2025, e202504895. https://doi.org/10.1002/anie.202504895).\nIGMH analysis reveals distinct interfacial bonding regimes: While the binding of PVA‒PEDOT is\nprimarily governed by hydrogen bonding and van der Waals interactions, PSS‒PVA exhibit\nsubstantially stronger bonding characteristics indicative of chemical bonding-consistent with prior\nreports (Figure R40C) (Adv. Mater. 2024, 36, 2304145. https://doi.org/10.1002/adma.202304145).\nSpecifically, sulfonate groups (‒SO ⁻) on PSS form chemical bonds with hydroxyl groups (‒OH) on\nsulfonate S=O stretching vibration emerges with increasing PEDOT:PSS content, demonstrating\nexceptionally strong sulfonate-hydroxyl interactions approaching covalent bond strength (Figure\nR40D).\nFigure R40. (A) Comparison of interaction energy between conductive polymer PEDOT:PSS and polymer PVA by\nDFT optimizations. (B) Structure of PEDOT–PSS, PEDOT–PVA and PSS–PVA btained DFT optimizations. (C)\nIGMH map showing intermolecular interactions of PVA–PEDOT and PVA–PSS, each molecule is defined as a\nfragment in the IGMH analysis. The coloring range is −0.05 to 0.05 a.u. The color bar indicates the sign(λ )ρ values,\n2\nwith blue representing prominent attractive interactions, red indicating prominent repulsive interactions in the\nregions with steric effect, and green exhibiting very weak interactions. (D) FTIR spectra of 20PP–DNH, 20PP–\n40 / 67\nDNE and 20PP.\n(3) Charge compensation mechanism. By combining experimental and theoretical findings, we\n56 / 67\nhave provided an in-depth interpretation of the charge compensation mechanism:\nIn short, PSS, acting as an intermediary, is covalently bonded within the PVA hierarchical network,\nthus enabling the hierarchical arrangement of PEDOT. PEDOT:PSS facilitates the diffusivity of Na+,\nand hinders the Cl–-migration via the holes on the PEDOT backbone in response to applying force,\nresulting in the higher mechnosensitivity. When there is no pressure to drive the Na+ migration, PSS\nexerts a constraint on Na+ in which Na+ is bound to the −SO – groups, increasing the diffusion barriers\n3\nof Na+ and facilitating the ion inactivation kinetics.\nSpecifically, this ion diffusion mechanism in electrical doping have been clearly revealed that the\nelectronic gating occurs via Na+/Cl– inserted or removed from PEDOT:PSS-binding site, in which\nNa+ and Cl–are the charge-compensating species of PEDOT:PSS. Notably, this charge compensation\nmechanism proceeds via an ion exchange reaction. Although the ion exchange reaction is\nthermodynamically spontaneous, sufficient concentrations of both ions and electrons are required to\nensure favorable reaction kinetics.\nMechanistically, Cl–, as the main charge-compensating species of the holes on the PEDOT backbone,\nextends the electronic transmission chain, and further accelerates Na+-ion transmission in response to\nan applied pressure. Additionally, nanoconfined Cl– ions struggle to migrate, providing significant\nenhancement in diffusivity difference between Na+ ions and Cl– ions, and contributing to the\nremarkable piezovoltage output. Whereas removing pressure, Na+ binding sites on the −SO – moieties\n3\non the PSS chains is activating to retard Na+-ion reverse migration, thereby amplifying ion\ninactivation kinetics and further guaranteeing the continuous pressure-driven piezovoltage output\n(Figure 41).\n57 / 67\nFigure R41. The molecular origins of piezoionicity in conductive, hierarchical PIEgels for applying pressure (top)\nand removing pressure (bottom). Na+ ions and Cl– ions are the charge-compensating species of PEDOT:PSS,\nachieving dynamic modulation of piezoionic activation/inactivation kinetics via pressure-responsive switching.\nWe also made the corresponding revised in the Structural and molecular determinant of piezoionic\nmechanism and Figure 5 in Revised Manuscript, and marked in red color.\nRevised Figure 5 and Piezoionic mechanism:\n58 / 67\nComment 2. The conductivity and piezoionic output of the material exhibit consistent trends relative\nto PEDOT:PSS. What underlying mechanistic link exists between these parameters? The authors are\nadvised to elaborate on this correlation.\nAuthors’ Response: Thank you for your valuable suggestions and positive feedback. To verify the\ndetermining factors of PEDOT and NaCl on piezoionic performance, we conducted the following\ncomparative experiments:\nWe engineered a NaCl-free eutectogel containing exclusively chloride ions (sourced from the choline\nchloride component of the deep eutectic solvent). We anticipated substantially degraded piezoionic\nperformances in NaCl-free eutectogel due to the absence of sodium-mediated charge compensation\nbetween Na+ and PSS in PEDOT:PSS. Furthermore, the 0PP–DNE control group (containing only\n59 / 67\nNaCl without PEDOT:PSS) exhibits a drastic deterioration in piezoionic performances (Figure R42A,\nR42B and R42C). These findings conclusively demonstrate that the synergistic coupling between\nPEDOT:PSS and Na+/Cl− is essential for enhanced piezoionic performances.\nFigure R42. (A to C) Ion-electron coupling validation: (A) Electronic conductivity (𝜎 ) and ionic conductivity (𝜎)\n𝑒 𝑖\nfor 0PP–DNE (No PEDOT:PSS), NaCl-free 20PP–DNE (No NaCl), and 20PP–DNE (PEDOT:PSS + NaCl). (B)\nPiezovoltage (∆V) and piezoionic coefficient for 0PP–DNE (No PEDOT:PSS), NaCl-free 20PP–DNE (No NaCl),\nand 20PP–DNE (PEDOT:PSS + NaCl). (C) mechnosensitivity (S) and inactivation time (T) for 0PP–DNE (No\nPEDOT:PSS), NaCl-free 20PP–DNE (No NaCl), and 20PP–DNE (PEDOT:PSS + NaCl). (D to E) Conductivity-\nPiezionics correlation. (D) Electronic conductivity (𝜎 ) and ionic conductivity (𝜎) for 0PP–DNE, 10PP–DNE and\n𝑒 𝑖\n20PP–DNE. (E) Piezovoltage (∆V) and piezoionic coefficient for 0PP–DNE, 10PP–DNE and 20PP–DNE. (F)\nmechnosensitivity (S) and inactivation time (T) for 0PP–DNE, 10PP–DNE and 20PP–DNE.\nContrary to the monotonic trend in mechanical properties, the piezoionic performances of PIEgels\n60 / 67\ndoes not increase with higher PEDOT:PSS loading. Instead, 10PP–DNE exhibits a reduction\ncompared to 0PP–DNE, followed by a substantial enhancement in 20PP–DNE. This trend aligns\nprecisely with the conductivity evolution. We attribute the non-monotonic behavior to ion transport\nkinetics: insufficient PEDOT:PSS content (10 wt%) induces charge-blocking effects, disrupting\nefficient charge compensation via ion-exchange between PEDOT:PSS and Na+/Cl− (Figure R42D).\nParticularly, the mechnosensitivity (S) during applying pressure and inactivation time (T) during\nremoving pressure of 20PP–DNE respectively shows 1457 mV s–1 and 2.569s, corresponding to\npiezoionic coefficient of 9.7 nV Pa–1 and piezovoltage (∆V) of 30 mV. The S and T of 10PP–DNE\nrespectively is 9.8 mV s–1 and 0.841s, corresponding to piezoionic coefficient of 1.9 nV Pa–1 and ∆V\nof 5.8 mV. Whereas the S and T of 0PP–DNE respectively is 900 mV s–1 and 0.485s, corresponding\nto piezoionic coefficient of 2.6 nV Pa–1 and ∆ V of 7.9 mV (Figure R42E and R42F). These\nexperimental findings confirm that 20 wt% PEDOT:PSS substantially promotes the piezoionic ion\ndiffusion kinetics in applying pressure, accompanied by outstanding ion inactivation kinetics after\nremoving pressure, whereas 10 wt% hinders ion diffusion kinetics, in comparison to PIEgels without\nPEDOT:PSS. This correlation further confirms that PEDOT:PSS is capable of altering ionic\nconduction via ion-exchange reaction, which is dependent on the concentration.\nWe also made the corresponding changes in the Piezoionic performances and piezoionic coefficients\nof PIEgels and Figure 5 in the Revised Manuscript.\n(Line 304) These experimental findings confirms that 20 wt% PEDOT:PSS substantially promotes\nthe piezoionic ion diffusion kinetics in applying pressure, accompanied by outstanding ion\ninactivation kinetics after removing pressure, whereas 10 wt% hinders ion diffusion kinetics, in\ncomparison to PIEgels without PEDOT:PSS. This correlation further confirms that PEDOT:PSS is\ncapable of altering ionic conduction via ion-exchange reaction, which is dependent on the\nconcentration (Supplementary Fig. 18). Furthermore, the variation trend of piezoionic performance\nwith the PEDOT:PSS concentration is consistent with the electrochemical properties.\nComment 3. As shown in Figures 4E and 4G, 10PP-DNE exhibits no enhancement in piezoionic\nperformance compared to 0PP-DNE, while its mechanical sensitivity declines significantly. The\nunderlying mechanism driving this counterintuitive phenomenon warrants detailed elucidation, yet\nthe manuscript currently lacks explicit discussion of this critical observation.\nAuthors’ Response: We thank you for pointing out this key. We sincerely appreciate your insightful\nsuggestions. This kinetic limitation arises from the ion-exchange reaction dynamics, which may\nbecome hindered when the concentrations of PEDOT:PSS and NaCl are imbalanced.\nPiezoionic experimental findings confirm that 20 wt% PEDOT:PSS (20PP−DNE) substantially\npromotes the piezoionic ion diffusion kinetics in applying pressure, whereas 10 wt% (10PP−DNE)\nhinders ion diffusion kinetics, in comparison to 0PP−DNE (Figure R42E and R42F). This correlation\n61 / 67\nfurther confirms that PEDOT:PSS is capable of altering ionic conduction via ion-exchange reaction,\nwhich is dependent on the concentration. To validate the charge separation mechanism, the free\nenergy of ion exchange ΔG between PEDOT:PSS, Na+ and Cl− is calculated from the standard Gibbs\nIE\nfree energy (ΔG0) of each species, using density functional theory (DFT) calculations, before and\nafter the exchange:\nΔG = ΔG0(PEDOT+Cl−) + ΔG0(Na+PSS−) − ΔG0(PEDOT:PSS) − ΔG0(Na+) − ΔG0(Cl−)\nIE\nwhere, Cl− and Na+ function as distinct species rather than NaCl pairs. This distinction arises because\nNa+ originates solely from NaCl pairs, while Cl− derives from both NaCl pairs and the ChCl\ncomponent of the DES. The strongly negative ΔG (−317.7 kJ mol−1) signifies highly favorable ion\nIE\nexchange kinetics, contributing the charge separation between Na+ and Cl− (Figure R43).\nFigure R43. Schematic illustration of DFTcalculations for the standard Gibbs free energy (ΔG ) of each species, i.e.,\nWe made the corresponding revised in the Electrochemical performances and conductive mechanism\nof PIEgels and Figure 3 in Revised Manuscript, and marked in red color. We made the corresponding\nchanges in the Supplementary Fig. 2 and Supplementary Fig. 15 in Revised Supplementary\nInformation.\nThe Revised Figure 3 as following:\n62 / 67\nComment 4. In terms of mechanical properties, materials should be considered for mechanical\nfatigue testing under long-term cyclic loading. In addition to mechanical stability, does the effect of\nion transport degrade at different temperatures?\nAuthors’ Response: We value your expert insights, particularly regarding the critical role of long-\nterm operational stability in practical applications. To comprehensively assess the long-term stability\nof PIEgels, we performed extended cycling tests in mechanical performances and piezoionic\nperformances.\n(1) Mechanical fatigue. Cyclic compression tests at 50% strain reveal pronounced energy dissipation\nduring cycles 2-100, followed by stabilization with negligible dissipation and hysteresis saturation\nbeyond 2 cycles (Figure R44). This demonstrates exceptional mechanical resilience through 1,000\ncompression cycles, establishing a robust mechanical foundation for continuous pressure-induced\npiezoionic performance.\n63 / 67\nFigure R44. (A) Stress‒strain curves of 1000 consecutive compression -relaxation cycles for 20PP–DNE at strain\nof 50% (B) related hysteresis values. The curves are horizontally shifted for clarity.\n2. Piezoionic performances. Under continuous 3 Hz cyclic compression at 2 MPa stress, the\npiezovoltage output maintained stable operation for 220 seconds before undergoing significant\nattenuation. Beyond this duration, the output voltage decayed to 50% of its peak piezovoltage\namplitude, with the system enduring > 700 compressive cycles while preserving pressure-induced\npiezoionic performance (Figure R45).\nFigure R45. (A) Piezovoltage response stability of individual PIEgels under successive step acting force with\nsinusoidal perturbations. (B) Typical force‒time curves under repeated step compressions at a pressure of ~ 2.0\nMPa. PIEgels size: 0.7 cm × 0.7 cm × 1.5 mm.\n64 / 67\n(2) Different temperatures. To investigate the effect of temperature on piezoionic performance, the\neutectogel was incubated at different temperatures (30°C, 60°C, 90°C, and 120°C) for 1 hour,\nfollowed by immediate testing of its piezoionic properties. Our study revealed that both the peak\npiezovoltage output and the mechanosensitivity increased progressively with rising temperature.\nHowever, a notable decrease in mechanosensitivity was observed at 90°C, followed by a subsequent\nincrease at 120°C. This indicates a fundamental alteration in the piezoionic mechanism.\nWe postulate that this phenomenon likely arises from the competition between the thermodynamics\nand kinetics of ion-exchange reactions during heating, thereby disrupting the charge compensation\nmechanism. When thermodynamics dominates at higher temperature, the mobility difference between\nchloride ions (Cl–) and sodium ions (Na+) may diminish. Consequently, both Na+ and Cl– undergo\nsimultaneous pressure-induced migration, leading to substantially enhanced mechanosensitivity\nwhile the peak piezovoltage remains largely unchanged. Conversely, when kinetics dominates at\nlower temperature, the migration of Na+ primarily mediates the piezovoltage generation.\nWe also made the corresponding changes in the Continuous piezovoltage and instantaneous response\nof PIEgels and Figure 6 in the Revised Manuscript, as well as Supplementary Fig. 17 and Fig. 30 in\nRevised Supplementary Information.\n65 / 67\nFigure R46. The influence of temperature on the piezoionic performances. (A and B) The piezovoltage output by\ncontinuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and ion\ninactivation kinetics (B) for 20PP–DNE under 30 ℃. (C and D) The piezovoltage output by continuously applying\nstep force stimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for\n20PP–DNE under 60 ℃. (E and F) The piezovoltage output by continuously applying step force stimulation (E)\nand corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (F) for20PP–DNE under 90 ℃. (G\n66 / 67\nand H) The piezovoltage output by continuously applying step force stimulation (G) and corresponding piezoionic\nion diffusion kinetics and ion inactivation kinetics (H) for 20PP–DNE under 120 ℃.\nComment 5. Does 'S' in Figure 4 stand for mechanical sensitivity? This is not stated. Similar to 'T'\nand 'V'. In addition, V should be changed to ∆V.\nAuthors’ Response: We appreciate your insightful suggestions and apologize for our presentation.\nWe have corrected this point in Revised Figure 4.\nComment 6. Line 417-423, 'When there is no mechanical energy to sustain these movements,\nPEDOT:PSS exerts a constraint on Na+ in which Na+ is bound to the SO3– groups on the PSS,\nincreasing the transfer energy barriers and generating the ion inactivation kinetics. Critically, this ion\ndiffusion mechanism in electrical doping have been clearly revealed that the electronic gating occurs\nvia ions inserted or removed from PEDOT:PSS-binding sites in ordered PEDOT-rich regions, in\nwhich Na+ ions and Cl− ions are the charge-compensating species at matched ionic and electronic\nconcentrations.' : If there could be further elaboration on this sentence, it would be beneficial.\nAuthors’ Response: Thank you for identifying parts of the manuscript that can benefit from a rewrite,\nas follow:\n(Line 397) Comprehensively, these observations allow us to draw the clear demonstration of the\nmolecular origins of piezoionicity in PIEgels, namely, hierarchical network orientation and charge\ncompensation mechanism (Fig. 5K). On the one hand, hierarchical architecture facilitates greater ion\nmigration by lowering the spatial energy barriers of ion transport. On the other hand, the charge\ncompensation mechanism dynamically modulates ionic diffusion kinetics by leveraging pressure. The\ncharge compensation mechanism operates through ion-exchange reaction. Although the ion-exchange\nreaction is thermodynamically spontaneous, sufficient concentrations of both ions and electrons are\nrequired to ensure favorable reaction kinetics. Mechanistically, Cl–, as the main charge-compensating\nspecies of the holes on the PEDOT backbone, extends the electronic transmission chain, and further\naccelerates Na+-ion transmission in response to an applied pressure. Additionally, nanoconfined Cl–\nions struggle to migrate, providing significant enhancement in diffusivity difference between Na+\nions and Cl– ions, and contributing to the remarkable piezovoltage output. Whereas removing pressure,\nNa+ binding sites on the −SO – moieties on the PSS chains is activating to retard Na+-ion reverse\n3\nmigration, thereby facilitating ion inactivation kinetics and further guaranteeing the continuous\npressure-driven piezovoltage output.\nWe also made the corresponding revised in the Structural and molecular determinant of piezoionic\nmechanism in Revised Manuscript, and marked in red color.\n67 / 67"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have fully addressed our comments. Therefore, the revised manuscript can be published in the Nature Communications journal.", "reviewer_2": "In this revised manuscript, the authors have added some tests and provided more detailed explanations to enhance the overall quality of work, and some of their responses to the previous comments are acceptable. However, several critical concerns remain unresolved, of which two are fundamental and critical:\n(1) Robustness of work: they adequately addressed the reliability and accuracy of their measurements. Certain replies are vague or unconvincing, leaving confusion or even doubts about the robustness/correctness/vigor of the work. Better prioritize correctness than publication speed.\n(2) The authors have not provided convincing evidence to support the structural design rationale of the materials and devices. This is clearly reflected in a significant lack in performance behind published work. Deficiencies in design rationale and performance both suggest limited scientific progress and novelty.\nBelow are detailed comments:\n1. The authors claim that the piezoionic performance of their gel is superior to that of previously reported hydrogels. However, this claim is not convincing. The reported maximum piezoionic coefficient in this work is only 9.8 nV Pa⁻¹, which is clearly not higher than many previous reports (Adv. Funct. Mater. 2023, 33, 2300701; Adv. Mater. 2024, 36, 2309821; Adv. Mater. 2024, 36, 2313127). Even more confusing is the emphasis on an output voltage of 40 mV under a pressure of 3.0 MPa—such a large pressure yielding a relatively modest voltage output raises questions about the actual performance level. This result does not align with the authors’ claim of “outstanding piezoionic performance.” Furthermore, in Figure R1c and R1d, the use of Young’s modulus and fracture strength on the x-axis, rather than the pressure corresponding to peak piezovoltage, further undermines the credibility of their performance comparison. The comparison table (Table R2) also contains questionable data; for example, the reported piezoionic coefficient from Angew. 2025 is listed as 5.0 nV Pa⁻¹, while the actual reported value reaches up to 1490 nV Pa⁻¹. Such misrepresentations significantly compromise the reliability of the comparative analysis.\n2. The authors suggest that Cl⁻ exhibits greater sensitivity than larger ionic complexes. However, this statement lacks both theoretical and experimental support. Ion sensitivity is highly dependent on the structural environment and binding interactions within the system. In fact, the authors themselves mention that Cl⁻ is generally constrained by PEDOT⁺ chains, which directly contradicts the idea that Cl⁻ could actively participate in pressure-sensitive transport in this gel. Therefore, even if Cl⁻ ions are inherently pressure-sensitive, their restricted mobility in this system renders the argument meaningless. Moreover, the authors’ approach of comparing only the advantages of their gel against either hydrogels or ionogels, without acknowledging the respective strengths of those systems, is logically flawed. In particular, the gel in this work does not demonstrate faster ion response than conductive hydrogels, nor does it outperform ionogels in output performance.\n3. Although the authors explained that no significant alignment could be observed in the 2D WAXS and SAXS patterns, relying solely on SEM to demonstrate orientation is not convincing. Alignment is one of the essential physical features of this gel, and SEM cannot provide sufficient evidence in this regard. Furthermore, DSC analysis is necessary to confirm the validity of the DES system. However, this key data is missing from Figure R11E, making the analysis incomplete.\n4. The justification for using PEDOT:PSS and choline chloride (ChCl) remains inadequate. In particular, the choice of ChCl is not well explained. If the proposed mechanism is that PEDOT⁺ cations bind Cl⁻ anions to control their migration, then smaller cations such as Na⁺ would appear more favorable, as choline has a larger ionic radius and forms stronger coordination with PEDOT:PSS. This strong interaction could hinder its mobility under pressure gradients. The authors have not addressed these key mechanistic issues regarding ion mobility in their system.\n5. The section on hierarchical structure is supposed to demonstrate its contribution to enhanced piezoionic performance. However, the supporting data and mechanistic explanation are insufficient. The manuscript fails to show how this structure affects the differential mobility of cations and anions, which is central to piezoionic enhancement. The use of SEM to claim a non-porous wall structure is problematic, as SEM resolution is far lower than the size of ions. It cannot resolve nanometer-scale voids or confirm their absence. Thus, the authors’ conclusion that this structure promotes directional ion transport is premature and lacks experimental support.\n6. The working principle of the test configuration in Figure 4 is still unclear. It remains unexplained how a pressure gradient is established within the conductive gel. In most two-terminal electrode configurations, pressure is applied on one side. Here, however, the pressure is applied at the center between two electrodes, which raises concerns about the actual mechanism responsible for voltage generation. In the 1000-cycle test, the input pressure trace from the test instrument offers limited interpretive value. It would be more meaningful to focus on the piezoionic signal itself. In fact, the reported signal suffers from baseline drift and instability, which casts further doubt on the signal reliability.\n7. Although the authors have described their measurement method, they did not provide specific testing parameters to justify the extremely high ionic conductivity of the gel. Typically, untreated PEDOT:PSS films have conductivities below 1 S cm⁻¹, and PEDOT:PSS hydrogels generally fall below 0.1 S cm⁻¹. In this work, the reported values, when combined with the impedance data, appear abnormally high and are not adequately justified.\n8. The manuscript also fails to clarify the ion conduction path under mechanical stress within the device. The current structure does not appear to constitute a piezoionic device with a proper series electrical configuration. Unfortunately, the authors’ reply does not address the question and leaves the core concern unresolved.", "reviewer_3": "In the manuscript, the authors developed a mechanically robust and mixed ionic-electronic conductive eutectogels for continuous piezoionicity. They balance the trade-off between robust mechanical properties and high piezoionic voltage output through hierarchical structure design and charge compensation mechanism. Some minor points need to be addressed before publication.\nComment 1. According to the \"charge compensation mechanism\" stated in the manuscript, why do the chloride ions bind to PEDOT when pressure is applied, and when the pressure is removed, the sodium ions interact with the PSS to prolong its inactivation time? The authors should provide more explanation about how the pressure influences the ion-chain interactions.\nComment 2. In addition, is the longer inactivation time a good thing for pressure sensing? Can it be used for memory functions similar to synapses?\nComment 3. The ionic conductivity of eutectogel is 29.09 S/cm, which is much higher than the reported ionic conductive gels (below 0.1 S/cm). And this number is calculated from equivalen circuit analysis, is it resonable?\nComment 4. In Figure 1G, why it takes several seconds to reach peak piezovoltage, which is contrary to the fast response time (0.02 s) in Figure 4D?"}, "author_response": "Point-by-Point Response to Reviewers' Comments\nDear Reviewers:\nWe deeply appreciate your time and effort in reviewing our manuscript and providing constructive\nfeedback on our manuscript entitled “Continuous piezoionicity-driven electromechanical coupling in\nmechanically robust conductive eutectogels (NCOMMS-25-18534A)”. Thank you very much for the\nencouraging comments that help to strengthen the quality of our manuscript. In response to these\nvaluable comments, we provide point-by-point responses along with the modifications made in the\nrevised manuscript and supplementary information, and marked in the red color. We sincerely hope\nthat the revised manuscript now meets the standards for publication.\nThank you very much for your help in improving this research. Thank you for your kind consideration!\nIn this response letter below,\n Response to Reviewer #2: Page 2 – 21\n Response to Reviewer #3: Page 22 – 27\nPlease note that:\n Reviewers' comments are in blue color.\n Authors’ responses are in black color.\n1 / 27\n Reviewer #2:\nIn this revised manuscript, the authors have added some tests and provided more detailed explanations\nto enhance the overall quality of work, and some of their responses to the previous comments are\nacceptable. However, several critical concerns remain unresolved, of which two are fundamental and\ncritical:\n(1) Robustness of work: they adequately addressed the reliability and accuracy of their measurements.\nCertain replies are vague or unconvincing, leaving confusion or even doubts about the\nrobustness/correctness/vigor of the work. Better prioritize correctness than publication speed.\n(2) The authors have not provided convincing evidence to support the structural design rationale of\nthe materials and devices. This is clearly reflected in a significant lack in performance behind\npublished work. Deficiencies in design rationale and performance both suggest limited scientific\nprogress and novelty.\nWe greatly appreciate you for meticulous review and intriguing comments, which has helped us to\nfurther improve our manuscript and research value. We have seriously taken your suggestions into\naccount and carefully revised our manuscript. Perhaps the vast amounts of data have caused confusion.\nNow, let's reorganize it for you. The main points of these two revisions are as follows:\n(1) Piezoionic testing methods. In Revision A, additional comparative experiments and assessments\nof piezoionic performance were incorporated to substantiate the charge compensation between ions\nand electrons and to demonstrate the superiority of the hierarchical structural design; thus, the\nnecessity of piezoionic testing is unequivocal. Regarding the testing methodologies, two approaches\nwere evaluated: one involving full coverage of pressure and the other applying pressure locally near\na specific electrode. Both methods were subsequently validated in other piezoionic tests and exhibited\nnegligible differences. For the measurement of the piezoionic coefficient, the latter method—\nlocalized pressure application at the electrode—is typically employed.\n(2) Piezoionic performances. Our work demonstrates a unique integration of mechanical robustness\nand piezoionic performance in PIEgels. While we highlight this advance, we also acknowledge the\nmerits of other reported piezoionic systems. In terms of piezovoltage output, our mechanically robust\nPIEgels perform comparably to existing piezoionic materials. The applied pressure required to\nactivate ion migration in our system is on the megapascal scale (MPa), as lower pressures are\ninsufficient to overcome the energy barrier for ion transport in such stiff materials. In contrast,\npreviously reported soft piezoionic hydrogels readily form pressure gradients under kilopascal-scale\npressures (kPa) due to their mechanical compliant charact. This difference in the operable pressure\nrange represents a fundamental distinction between the two types of piezoionic materials, reflecting\ntheir different response thresholds to applied pressure, which should not be equated with mechanical\n2 / 27\nsensitivity.\nThus, the concern that such high pressures yield relatively low voltages can be understood within this\ncontext. It is worth emphasizing that, for pure piezoionic mechanisms, a piezovoltage output of\nseveral tens of millivolts (mV) is already competitive; further improvements in performance remain\na goal for future research.\n(3) Electrical and Electrochemical Characterization and Fitting. In Revisions A, we expanded\nthe suite of electrochemical tests primarily to demonstrate the ion-exchange reaction and the ion-\nelectron coupling effects. The primary focus was placed on these mechanisms rather than on the\nspecifics of conductivity calculation—we appreciate the reviewer’s reminder on this point. In the\ncurrent revision, we conducted extensive electrochemical measurements across multiple batches to\nvalidate ionic conductivity, and additionally employed a four-probe method to determine the intrinsic\nelectrical conductivity. These two types of conductivity hold distinct scientific significance: the four-\nprobe method measures the intrinsic electrical conductivity (~ 0.164 ± 0.0276 S cm–1), whereas the\nconductivity derived from electrochemical impedance spectroscopy (EIS) fitting reflects the ionic\nconductivity (~ 0.0038  0.00029 S cm–1) within the electrochemical system, specifically\ncharacterizing the impedance of ion transport. We have accordingly corrected the presentation and\ndiscussion of electrical conductivity values in Figure 1F of Revised Manuscript.\nWe have also corrected the electrochemical testing data for the PIEgels in Figure 3G to 3I of Revised\nManuscript. We sincerely apologize for the errors in the electrochemical testing and greatly\nappreciate your professional feedback, which has been invaluable in improving our work.\nAdditionally, this was instrumental in clarifying our understanding and preventing misinterpretation\nregarding conductivity.\n(4) Structure and Device design. The primary focus of our work is to resolve the conflict between\nmechanical properties and piezoionic performance in piezoionic materials.\nTo this end, we employed mechanical training to align the polymer network into a hierarchical\nstructure, which not only ensures mechanical robustness but also confines ion transport pathways,\nthereby reducing the energy barrier for ion migration. In Revision A, this concept was validated\nthrough comparative experiments: PIEgels with and without a hierarchical structure. Compared to\nnon-hierarchical PIEgels, those with hierarchical structures exhibit a 3.6-fold increase in ∆V, a 3.5-\nfold enhancement in piezoionic coefficient, and a 2.2-fold improvement in S. However, they require\na 22-fold longer T. In the current revision, we have supplemented this with molecular dynamics (MD)\nsimulations, whose results—including diffusion coefficients and piezoionic dynamics in hierarchical\nstructure, a finding consistent with both experimental measurements and DFT calculations—fully\ncorroborate the superiority of the designed architecture and confirm the proposed synergistic\nmechanism. Our simulations not only visualize ion migration within the hierarchical structure but\nalso confirm the charge compensation mechanism.\nAdditionally, the cascaded architecture has been reported in numerous bioelectronic devices; in our\napproach, the electrical series connection is achieved through direct conductive pathways.\nCorresponding pressure stimulation tests can be used to validate the rationality of the device design.\nSpecifically, when comparing individual PIEgels and serially connected PIEgels under mechanical\nstimulus, a clear series-connection effect is observed in the piezovoltage output, confirming the\nenhanced performance of the cascaded structure.\n4 / 27\nComment 1A. The authors claim that the piezoionic performance of their gel is superior to that of\npreviously reported hydrogels. However, this claim is not convincing. The reported maximum\npiezoionic coefficient in this work is only 9.8 nV Pa⁻¹, which is clearly not higher than many previous\nreports (Adv. Funct. Mater. 2023, 33, 2300701; Adv. Mater. 2024, 36, 2309821; Adv. Mater. 2024,\n36, 2313127).\nAuthors’ Response: Thanks for your comments. What we are stating is that “The resultant PIEgels\nachieve the integration of exceptional mechanical performances and piezovoltages, outperforming\nsome reported piezoionic hydrogels.” in the manuscript. To avoid any ambiguity, we have rephrased\nthis sentence in Revised Manuscript, as fellow: In contrast to previously reported piezoionic\nhydrogels, the resultant PIEgels achieve a harmonious integration of mechanical robustness and\npiezoionic performance, thereby resolving the inherent conflict between these two properties. Taking\ninto account both mechanical properties and piezoionic properties in Ashby plots, PIEgels\ndemonstrate clear advantages compared to existing piezoionic hydrogels.\nThe piezoionic coefficient solely quantifies the linear pressure-voltage relationship within a specific\npressure range and does not fully capture the comprehensive piezoionic performance. That is, within\ndifferent pressure ranges, the response of the pressure voltage to the pressure is different. This\nphenomenon also has been reported in (Angew. Chem. Int. Ed. 2025, 64, e202415000.\nhttps://doi.org/10.1002/anie.202415000).\nFor our work, under a small pressure input of 0 – 1 MPa, the magnitude of piezovoltage is almost\nclose to zero, indicating that there is no generated voltage. A positive close-to-linear correlation\nbetween ∆P and ∆V under pressure input of 1 – 5 MPa, with the higher degree of pressure was\naccompanied by a rapid increase in the piezovoltage output, from 0 to 47 mV, and piezoionic\ncoefficient of 10.9 nV Pa–1. As the pressure continues to increase, the piezovoltage increases slowly\nwith a low piezoionic coefficient of 1.44 nV Pa–1 (Figure R1).\nFurthermore, the superior piezoionic performance of our PIEgels manifests in two key aspects\ncompared to prior studies:\n(1). Peak piezovoltage magnitude: PIEgels generate peak piezovoltages of ~40 mV. This significantly\nexceeds reported values, such as the ~ 3 mV for mechanoreceptors (Science, 2022) and ~3 mV for\nPVA-CE (Angew. Chem., 2025), constrained by their comparatively weaker mechanical properties.\n(2). Continuous piezovoltage: Owing to exceptional mechanical robustness, PIEgels maintain\ncontinuous piezovoltage output under successive stepping pressure, with peakvoltages persisting for\n~ 200 s. In contrast, existing piezoionic materials typically exhibit only transient piezovoltage\nresponses.\nThe polyvinylidene fluoride-hexafluoropropylene (PVDF)-based ionogels, such as PVDF-co-CTFE\nionogel in Adv. Mater. (2024, 36, 2309821) and PVDF-HFP/EMIMTFSI ionogel in Adv. Mater.\n5 / 27\n(2024, 36, 2313127) are a type of piezoelectric-piezoionic mixed ionogel, not a pure piezoionic gel.\nThe mechanism by which it generates electricity lies in the implantation of the piezoelectric material\nPVDF. Metal ions coordination hydrogel (HG-MI) piezoionics in Adv. Funct. Mater. (2023, 33,\n2300701) generates peak piezovoltages of 44.35 mV under 50 kPa, exhibiting the outstanding\npiezovoltage. Therefore, in our manuscript, a comparison was made. Compared with HG-MI, the\nPIEgels we designed have higher mechanical properties, which may open up new applications for\npiezoionics. Different mechanical properties may support different application scenarios. The soft gel\nmay be suitable for skin bioelectronic and biosensors. The tough gel can be applied to the monitoring\nof intense physical activities.\nComment 1B. Even more confusing is the emphasis on an output voltage of 40 mV under a pressure\nof 3.0 MPa—such a large pressure yielding a relatively modest voltage output raises questions about\nthe actual performance level. This result does not align with the authors’ claim of “outstanding\npiezoionic performance.”\nAuthors’ Response: We acknowledge that the Introduction section may not have sufficiently\nemphasized a key achievement: the PIEgels overcome the traditional trade-off between mechanical\nrobustness and piezoionic performance. As noted, most piezoionic materials generate voltage under\nminimal pressure due to inherent mechanical softness—a design feature enabling responsiveness.\nHowever, achieving high piezoionic output in mechanically robust systems remains a fundamental\nchallenge. To address this, we engineered a hierarchical fibrous architecture coupled with molecular-\nlevel charge compensation mechanisms, thereby reconciling exceptional mechanical toughness with\nhigh piezoionic sensitivity.\nConsequently, the observed peak piezovoltage of 40 mV at 3 MPa may appear modest. Critically,\nhowever, this value represents one of the highest reported outputs among pure piezoionic gels. This\npeak piezovoltage of 40 mV is generated by via successive step acting force (Figure 1G in the\nManuscript). With a single pressure stimulation, it will only produce around 30 mV (Figure 4C and\n4D in the Manuscript). The inherent mechanical robustness of PIEgels necessitates a minimum\npressure threshold (>1 MPa) to activate ion migration and generate piezoionic response. Thus,\nsignificant piezovoltage generation occurs only beyond this critical stress level, aligning with the\nmaterial’s designed compatibility between mechanical strength and ion conduction performance.\nComment 1C. Furthermore, in Figure R1c and R1d, the use of Young’s modulus and fracture\nstrength on the x-axis, rather than the pressure corresponding to peak piezovoltage, further\nundermines the credibility of their performance comparison. The comparison table (Table R2) also\ncontains questionable data; for example, the reported piezoionic coefficient from Angew. 2025 is\nlisted as 5.0 nV Pa⁻¹, while the actual reported value reaches up to 1490 nV Pa⁻¹. Such\nmisrepresentations significantly compromise the reliability of the comparative analysis.\nAuthors’ Response: As established, PIEgels are characterized by the concurrent achievement of\n6 / 27\nmechanical robustness and piezoionic functionality. Consequently, Figures 1H and 1I present Ashby\nplots correlating mechanical properties with piezoionic performance, highlighting the distinctive\nposition of PIEgels within these piezoionic gels.\nThe relationship between applied pressure and piezovoltage response is quantified in Figure 4J in the\nmanuscript, demonstrating the peak piezovoltage output of PIEgels across distinct pressure regimes.\nFigure R1. Piezoionic coefficients of PIEgels with respect to pressure in Figure 4J.\nThe reported piezoionic coefficients in Angew. 2025 are as follows: 1490 nV Pa–1 under 0 ~ 5 kPa,\n63 nV Pa–1 under 5 ~ 10 kPa, and 5 nV Pa–1 under 10 ~ 100 kPa. Therefore, considering the wide\nrange of the pressure, we chose 5 nV Pa–1. Therefore, we have provided annotations and explanations\nin the Table S1.\nFigure R2. Piezoionic coefficients with respect to pressure in Angew. Reproduced with permission from\nAngew. Chem. 2025, 64, e202415000. Copyright 2024 Wiley-VCH GmbH.\nComment 2A. The authors suggest that Cl⁻ exhibits greater sensitivity than larger ionic complexes.\nHowever, this statement lacks both theoretical and experimental support. Ion sensitivity is highly\ndependent on the structural environment and binding interactions within the system. In fact, the\nauthors themselves mention that Cl⁻ is generally constrained by PEDOT⁺ chains, which directly\ncontradicts the idea that Cl⁻ could actively participate in pressure-sensitive transport in this gel.\nTherefore, even if Cl⁻ ions are inherently pressure-sensitive, their restricted mobility in this system\n7 / 27\nrenders the argument meaningless.\nAuthors’ Response: We sincerely regret any confusion arising from our initial description. To clarify:\nthis statement solely emphasized choline chloride (ChCl) selection as a hydrogen-bond acceptor\nwithin the eutectic composition, rather than emphasizing chloride-selective migration as a primary\npiezoionic mechanism. As established by Prof. John Madden in Science 2022, ionic polarity remains\nthe dominant factor governing ion-selective migration in piezoionic gels. Compared to alternative\nsome hydrogen-bond acceptors in DES, ChCl exhibits a smaller ionic radius, thus conferring\nenhanced mechanosensitivity.\nIn PIEgels, the migration of Na+ ions is significantly higher than that of Cl⁻, which can be attributed\nto the confinement of Cl⁻ ions by PEDOT chains through charge compensation. Importantly, this\nionic differential migration is responsible for the generation of the piezoionic effect. These insightsare\nrobustly supported by ion–electron coupling effects via ion-exchange reactions (Figure 3 in the\nRevised Manuscript), DFT calculations and spectroscopic analyses (Figure 5 in the Revised\nManuscript). Furthermore, the present MD simulations comprehensively corroborate the proposed\npiezoionic mechanism (Figure 6 in the Revised Manuscript).\nRegarding the piezionic kinetics, a detailed discussion of MD stimulations is provided in our\nResponses to Comments 4 and 5.\nComment 2B. Moreover, the authors’ approach of comparing only the advantages of their gel against\neither hydrogels or ionogels, without acknowledging the respective strengths of those systems, is\nlogically flawed. In particular, the gel in this work does not demonstrate faster ion response than\nconductive hydrogels, nor does it outperform ionogels in output performance.\nAuthors’ Response: Thank you for your insightful comment on this aspect and we completely agree,\nand thank you for reminding us. We agree that our comparison was not comprehensive and appreciate\nthe opportunity to clarify this point. We acknowledge that a fair comparison should objectively\npresent the advantages and disadvantages of all systems involved.\nA key point to highlight is the outstanding mechanosensitivity (1457 mV s⁻1) demonstrated by our\nPIEgels. Our original intention was to highlight the unique combination of properties offered by our\nPIEgels, particularly in the perfect combination of mechanical performances and piezoionicity. It\nmust be acknowledged that piezoionic hydrogels possess distinctive advantages that have led to their\nwidespread adoption in flexible bioelectronics, particularly for in vivo applications. These benefits\nare largely attributed to their exceptional biocompatibility, mechanical flexibility, and enhanced\nwearing comfort.\nIn comparison to PVDF-based piezoelectric-piezoionic mixed ionogels, the pure piezoionic gels\nexists relatively weak piezo-related properties. Therefore, considering the fundamental differences\nin the mechanism, we did not conduct a comparison with this type of ionogels.\n8 / 27\nRegarding the characteristics of alternative piezoionic gels, we acknowledge that prior discussions\nwere limited. To address this gap, the Introduction section has been revised as follows:\nParticularly, piezoionic hydrogel functions through converting the applied force into ion streams,\nenabling an important role in flexible bioelectronics and biosensor, such as silent-speech recognition\nsystem transforming laryngeal mechanical vibrations into silent speech, and neuromodulation\ninterface eliciting hindlimb movement via tactile-induced current pulses, owing to exceptional\nbiocompatibility, mechanical flexibility. Despite their promising potential, soft piezoionic gels face\nsignificant challenges, including limited mechanosensitivity and short-term pressure-induced\npiezovoltages under prolonged or varying pressure simulation. This phenomenon stems from an\ninherent compromise between mechanical robustness and piezoionic performance: soft materials\nreadily establish a pronounced pressure gradient under stress, whereas stiff materials resist forming a\nsignificant pressure gradient.\nMechanically weak piezoionics fail to render the contribution to continuous ionic currents production\nin response to mechanical forces, along with mechanical failure under persistent loading. Whereas\nthe mechanosensitivity and ionic transmission may be sluggish in mechanically strong piezoionic\ngels owing to the weak pressure gradient caused by stress concentration.\nComment 3A. Although the authors explained that no significant alignment could be observed in the\n2D WAXS and SAXS patterns, relying solely on SEM to demonstrate orientation is not convincing.\nAlignment is one of the essential physical features of this gel, and SEM cannot provide sufficient\nevidence in this regard.\nAuthors’ Response: We acknowledge these concerns. We also agree with your insightful comment\nregarding the importance of atomic-scale ordered structure and the limitation of SEM in resolving\nsuch fine features. We fully agree that direct characterization of ionic ordering at the atomic scale\nremains challenging with currently available techniques.\nOur survey of hierarchical polymer network characterization across relevant literature confirms that\nSEM and SAXS constitute the established methodologies. Given that fiber dimensions intrinsically\nspan submicron to micron scales (100 ~ 1000 nm), these techniques adequately resolve critical\nstructural features. The hierarchical fiber alignment of PIEgels occurs at the micron scale, consistent\nwith the intrinsic dimensions of fiber bundles (typically several micrometers). This structural\norganization is definitively resolved by SEM characterization. Post-mechanical training, nanoscale\nfibers maintain hierarchically oriented configurations—a conclusion directly discernible from SEM\nimages and SAXS scattering anisotropy in Figure 2 of the Revised Manuscript. In our study, the term\n\"hierarchical structure\" primarily refers to the microscale-to-nanoscale alignment of the fiber\nnetwork—not the arrangement of individual ions—as clearly demonstrated in the planar and cross-\nsectional SEM images (Figure R3). We have clarified this point in the revised manuscript to avoid\npotential misunderstanding.\n9 / 27\nOur focus is to clarify that the precise arrangement of ions cannot be directly probed. Instead, we can\nonly propose that pressure induces interlayer migration of ions, as the energy barrier for migration\nbetween layers is comparatively lower than that for disordered motion within a three-dimensional\nnetwork. Ion migration likely occurs preferentially through interfiber channels or interlamellar\nspaces—where reduced steric constraints promote directional transport. While this mechanistic\ninference requires further validation, current experimental measurements face fundamental\nlimitations in resolving such confined ion dynamics in hierarchical structure. Our future work will\ndevelop specialized approaches to quantitatively verify these structure-property relationships.\nFigure R3. Cross-sectional scanning electron microscopy (SEM) of PIEgels.\nComment 3B. Furthermore, DSC analysis is necessary to confirm the validity of the DES system.\nHowever, this key data is missing from Figure R11E, making the analysis incomplete.\nAuthors’ Response: In our prior Revision A, we included comprehensive DSC analysis across\ndiverse DES formulations. We recognize these data may have been obscured by their volume; they\nare presented in Figure R4C and Figure R4D (derived phase diagram). Critically, the phase diagram\nin Figure R4E is directly derived from the phase transition temperatures quantified in Figure R4D.\n10 / 27\nFigure R4. (A) FT-IR spectra of 20PP, 20PP–DNE and 20PP–DNH. (B) Various optical photographs, including\nGCA (Gly/ChCl /AAc), GC (Gly/ChCl), GCA2000 (Gly/ChCl /PAAc-2000) and GCA45000 (Gly/ChCl /PAAc-\n450000). (C) Differential Scanning Calorimetry (DSC) tests of GCA, GC, GCA2000 and GCA45000. (D)\nDifferential Scanning Calorimetry (DSC) tests of GA, GAC1, GAC2, GAC3, GAC4, GAC5, GAC6, GAC7, GAC8,\nGAC9, and GAC10. Note: α : β = 1 : 0, 1 : 1, 1 : 2, 1 : 3, 1 : 4, 1 : 5, 1 :6, 1 : 7, 1 : 8, 1 : 9, and 1 : 10. (D) The binary\nphase diagram derived from DSC testing (Gly/AAc = 4 : 1 as α component, and ChCl as β component).\nComment 4. The justification for using PEDOT:PSS and choline chloride (ChCl) remains inadequate.\nIn particular, the choice of ChCl is not well explained. If the proposed mechanism is that PEDOT⁺\ncations bind Cl⁻ anions to control their migration, then smaller cations such as Na⁺ would appear\nmore favorable, as choline has a larger ionic radius and forms stronger coordination with PEDOT:PSS.\nThis strong interaction could hinder its mobility under pressure gradients. The authors have not\naddressed these key mechanistic issues regarding ion mobility in their system.\nAuthors’ Response: We again appreciate your constructive suggestions. We sincerely apologize for\nany confusion caused by our previous revision. The selection of materials is indeed critical. Our\nchoice of Cl⁻ ions and PEDOT:PSS was primarily motivated by the ion-exchange reaction between\nthem—a key factor thoroughly established in the cited literature. Furthermore, choline chloride (ChCl)\nstands as the most common hydrogen-bond acceptor in deep eutectic solvents (DES). Regarding ion\nmobility, the disparity in ion mobility arises from the constrained migration of Cl⁻ ions, whereas Na⁺\nions migrate more freely under applying pressure. This mechanism has been further corroborated by\nthe newly conducted molecular dynamics (MD) simulations.\n(1) Rationality. The choice of eutectogel and the corresponding components is crucial. We regret\nthat our explanation in the previous revision may have been unclear. The primary advantage over\nconventional hydrogels lies in its ability to facilitate highly efficient ion-electron coupling. Therefore,\nwe have highlighted the advantages of the eutectogel by comparison with hydrogel. Furthermore, we\nprovide a detailed rationale for the selection of PEDOT:PSS and choline chloride, explaining their\nspecific roles and suitability within our study: Through comparisons between hydrogels and\neutectogels using electrochemical impedance spectroscopy analysis, we found that choline chloride\n(ChCl) in the deep eutectic solvent underpins the ion-electron coupling effect, which not only\nenhances electrical conductivity but also reduces ion transport impedance. This can be attributed to\nthe chloride ions from ChCl serving as charge compensation species for PEDOT chains, enabling\nhighly efficient ion-exchange reactions (Figure 3I and 3J in the Revised Manuscript). In summary,\nthe use of eutectogels enables the design of mixed ionic-electronic conductors to achieve piezoionic\nperformance.\nWe also made the corresponding changes in the section Ionic transport resistance and ion-electron\ncoupling of PIEgels and Figure 3 in the Revised manuscript, marked with red color.\n11 / 27\n(2) Ion mobility. We employed molecular dynamics (MD) simulations to investigate the piezoionic\ndiffusion kinetics of PIEgels during the loading and unloading.\nDuring compression, the MSD of both Na+ and Cl− ions was markedly higher than that observed\nduring pressure release, clearly demonstrating accelerated ion migration under applied mechanical\nstress (Fig. 6C). To further elucidate the characteristics of piezionic diffusion kinetics, we quantified\nthe diffusion coefficient through mean squared displacement (MSD) calculations. Specifically, we\ninvestigated the piezoionic kinetics by monitoring the time-dependent diffusion coefficients. During\nthe initial 0 – 1 ns period, the diffusion coefficients of both Na+ and Cl− ions remain near-zero,\nindicating that the applied pressure is insufficient to drive ion differential migration. The absence of\ndiffusivity difference (∆D) between the cationic and anionic diffusion coefficients precludes the\npiezovoltage generation. Subsequently, as the applied pressure increased between 1 – 2 ns, the\nacceleration of ion transmission is accompanied by a rapid increase in diffusion coefficients,\ncontributing to a progressively enlarging ∆D, with 0.38 × 10–12 cm–2 s–1 at 2 ns (i.e., 1.60 × 10–12 cm–\n2 s–1 for Na+ ions and 1.22 × 10–12 cm–2 s–1 for Cl− ions). During the final 2 – 2.5 ns period, ion\ndifferential migration decelerated despite further increases in pressure, accompanied by a\nconcomitant reduction in ∆D with 0.18 × 10–12 cm–2 s–1 at 2.5 ns (i.e., 1.84 × 10–12 cm–2 s–1 for Na+\nions and 1.66 × 10–12 cm–2 s–1 for Cl− ions). In summary, the piezoionic dynamics observed in our\nMD simulations are in remarkable agreement with the experimentally measured piezovoltage and\npiezoionic coefficients across varying pressures, as shown in Fig. 4J. Following the release of\npressure at 2.5 – 5 ns, ion migration decelerated markedly, accompanied by a substantial decrease in\nionic diffusion coefficients. Interestingly, however, the diffusion coefficient of Cl− ions (i.e., 0.19 ×\n10–12 cm–2 s–1 at 4.0 ns) exceeded that of Na+ (i.e., 0.15 × 10–12 cm–2 s–1 at 4.0 ns), indicating\npreferential confinement of Na+ ions after releasing the pressure, a finding consistent with both\nexperimental spectroscopies and DFT calculations (Figure R5).\n12 / 27\nFigure R5. Piezoionic diffusion kinetics via MD simulation for PIEgels with hierarchical structure.\nComment 5. The section on hierarchical structure is supposed to demonstrate its contribution to\nenhanced piezoionic performance. However, the supporting data and mechanistic explanation are\ninsufficient. The manuscript fails to show how this structure affects the differential mobility of cations\nand anions, which is central to piezoionic enhancement. The use of SEM to claim a non-porous wall\nstructure is problematic, as SEM resolution is far lower than the size of ions. It cannot resolve\nnanometer-scale voids or confirm their absence. Thus, the authors’ conclusion that this structure\npromotes directional ion transport is premature and lacks experimental support.\nAuthors’ Response: We deeply appreciate your expert suggestions. The hierarchical architecture is\nparamount for reconciling mechanical and piezoionic properties in PIEgels. Our study substantiates\nthat this hierarchical structure not only enhances mechanical performance but also amplifies\npiezoionic response. Specifically, it augments mechanical sensitivity and modulates inactivation time,\nthereby elevating peak piezovoltage output and piezoionic coefficients.\nWe appreciate your comment regarding the characterization of the hierarchical structure. In response,\nwe would like to clarify that the micron-scale hierarchical organization resulting from the mechanical\nalignment of nanofibers is clearly visible in both planar and cross-sectional SEM images, as shown\nin Figure R3. However, we fully agree that ionic-scale hierarchical phenomena—such as the ordered\ndistribution of ions within the confined nanochannels—are not resolvable via SEM and do indeed\n13 / 27\nrequire more advanced characterization techniques. We have revised the manuscript to focus more\nexplicitly on ion transport behaviors using MD stimulations that indirectly reflect the sub-microscopic\nordering, and have also included a discussion on the current limitations in probing atomic-scale ionic\narrangements (see the Comment 3).\n(1) Structure effect. In Revision A, this concept was validated through comparative experiments:\nPIEgels with and without a hierarchical structure. Compared to non-hierarchical PIEgels, those with\nhierarchical structures exhibit a 3.6-fold increase in ∆V, a 3.5-fold enhancement in piezoionic\ncoefficient, and a 2.2-fold improvement in S. However, they require a 22-fold longer T (Figure R6).\nFigure R6. The influence of hierarchical structure on the piezoionic performances. (A and B) The piezovoltage\noutput by continuously applying step force stimulation (A) and corresponding piezoionic ion diffusion kinetics and\nion inactivation kinetics (B) for trained 20PP–DNE. (C and D) The piezovoltage output by continuously applying\nstep force stimulation (C) and corresponding piezoionic ion diffusion kinetics and ion inactivation kinetics (D) for\n14 / 27\nuntrained 20PP–DNE. (E and F) Comparison of piezoionic performances between trained and untrained 20PP–\nDNE. (E) Piezovoltage and piezoionic coefficient. (F) mechanosensitivity and inactivation time.\nQuantifying differential mobility remains technically prohibitive at present. Prof. Madden and\ncolleagues characterized self-diffusion coefficient determination using in situ Nuclear magnetic\nresonance (Science 376, 502-507 (2022). DOI:10.1126/science.aaw1974), which presents significant\npractical challenges for our study. And Prof. Derek Ho (Angew. Chem. 2025, 64, e202415000)\nutilized MD simulations to quantify mobility differences. Therefore, we also conducted molecular\ndynamics simulations to visualize the ion migration at the hierarchical structure, in order to obtain\nthe ionic diffusion coefficient during loading and unloading processes.\n(2) MD stimulations. In this revision, we employed molecular dynamics (MD) simulations to\ninvestigate the piezoionic diffusion kinetics in hierarchical structure (Figure R5). The simulation\nsystems in our work contain sufficient DES molecules, 10 PVA chains, 10 PEDOT:PSS chains and\ncollaboration between hierarchical structure and charge compensation—we computationally\ndesigned and realized a simulation system featuring such a hierarchical architecture. Indeed,\ncompared to the system reported in Angew. Chem. (2025, 64, e202415000), the presence of a\nhierarchical structure in PIEgels requires significantly higher pressures to induce ion migration. The\nsimulated force required here is approximately 67000 kJ mol–1 nm–1, markedly higher than the value\nof 1000 kJ mol–1 nm–1 reported in Angew. Chem. (2025, 64, e202415000). This underscores a\nstructural advantage of PIEgels: the applied force effectively generates a substantial pressure gradient,\nwhich not only ensures mechanical robustness but also reduces the spatial energy barrier for ion\nmigration.\nAnother critical contribution is charge compensation arising from ion-exchange reactions, therefore,\nwe performed MD simulations with varying numbers of NaCl to probe reaction kinetics. As NaCl\nincreased from 30 to 60, the diffusivity difference becomes negligible, suggesting kinetically\nunfavorable ion-exchange reactions (Supplementary Fig. 37 and Supplementary Fig. 38 in\nSupplementary Information).\nCollectively, MD simulation further corroborates piezoionic characteristics and underlying\nsynergistic mechanism for PIEgels, demonstrating the pronounced asymmetry in the diffusion\nkinetics for decoupling the continuous pressure-driven ion migration. Such behavior—where the\nelectromechanical coupling is activated only under sufficient pressure stimulation—stems from the\nsynergistic effects of well-organized ion migration within hierarchical structure and efficient charge\ncompensation between ion and electron.\nWe also made the corresponding changes in the section Piezoionic diffusion kinetics via molecular\ndynamics simulation, Discussion and Figure 6 in the Revised manuscript, as well as Supplementary\nFig. 36 to 38, marked with red color.\n15 / 27\n(3) EIS fitting. Experimentally, Reviewer 1 proposed electrochemical methods to probe cation/anion\nmobility disparities. We implemented these tests but found the resulting data inadequate for\nquantitative mobility determination due to confounding multi-physical couplings. This limitation was\ncommunicated to Reviewer 1, who acknowledged the interpretational constraints. Qualitatively,\nhowever, the measurements indicated markedly higher diffusivity for Na⁺ than Cl⁻. Following\nelectrochemical impedance spectroscopy (EIS) protocols, we fitted the low-frequency region to\nextract the Warburg coefficient; diffusion coefficients were subsequently calculated using the\nfollowing equation:\n𝑅2𝑇2\n𝐷 =\n2𝐴2𝑛4𝐹4𝑐2𝜎2\n𝑤\nwhere, D (cm2 s−1) is the diffusion coefficient; R is the gas constant (R = 8.314 J mol−1 K−1); T is the\nabsolute temperature (T = 273.15 K); A (cm2) is the electrode surface area; n is the number of\nelectrons transferred per molecule in the reaction; F is the Faraday constant (F = 96485 C mol−1); c\nis the concentration of ions in the electrode material; σ is the Warburg coefficient, which corresponds\nw\nto the real part of the impedance Z , and its value is is determined by the slope in the plot of w−1/2\nre\nversus Z (Figure R7).\nre\nFigure R7. (A) The plot of w−1/2 versus Z . (B) Diffusion coefficient of sodium ions and chloride ions.\nre\nComment 6A. The working principle of the test configuration in Figure 4 is still unclear. It remains\nunexplained how a pressure gradient is established within the conductive gel. In most two-terminal\nelectrode configurations, pressure is applied on one side. Here, however, the pressure is applied at the\ncenter between two electrodes, which raises concerns about the actual mechanism responsible for\nvoltage generation.\nAuthors’ Response: We sincerely appreciate your rigorous and expert critique. The perceived\nambiguity likely stems from indirect graphical representation. Two distinct indentation protocols\nwere designed:\n1. Localized Electrode Loading (Figure 4J to 4K, and Supplementary Figure 20): Pressure applied\nnear one electrode to precisely quantify piezoelectric coefficients.\n16 / 27\n2. Global Uniform Loading (Fig. 4C to 4H): Mimics real-world conditions where pressure distributes\nacross the entire sample.\nCritically, both methods yield marginal differences in piezovoltage output—validating the robustness\nof PIEgels under operational stress configurations.\nComment 6B. In the 1000-cycle test, the input pressure trace from the test instrument offers limited\ninterpretive value. It would be more meaningful to focus on the piezoionic signal itself. In fact, the\nreported signal suffers from baseline drift and instability, which casts further doubt on the signal\nreliability.\nAuthors’ Response: We deeply appreciate your expert and constructive feedback. Pressure values\nwere directly recorded from the load cell supporting the test specimen. Given the ultrathin sample\ngeometry (≤2 mm), specimens were mounted flush against the sensor interface. Concurrently, we are\nfinalizing a dedicated piezoionic test platform enabling multi-parametric control—including pressure\nmagnitude and loading rate modulation—for enhanced mechanistic studies. Future work will\nestablish integrated operando characterization platforms, enabling real-time correlation of pressure\ndynamics with piezoionic output under programmable stimuli.\nWe appreciate this insightful observation. Baseline potential fluctuations are inherent to piezoionic\nsystems due to their self-powered nature, generating intrinsic electrochemical potentials that preclude\nperfect signal stability. Critically, raw piezovoltage data were intentionally preserved without\nnormalization to reflect true operational states, as verified by the consistent piezovoltage profiles\nunder sustained pressure in Figures 4C to 4H. This approach notably diverges from the normalization\nprotocols, which may obscure absolute piezovoltage magnitudes.\nWhile baseline instability is inherent (attributable to spontaneous electrochemical potentials in self-\npowered piezoionic systems), our unprocessed data robustly demonstrate stable piezovoltage (∆V)\ngeneration under applied pressure, that is, ∆V is determined value.\nComment 7. Although the authors have described their measurement method, they did not provide\nspecific testing parameters to justify the extremely high ionic conductivity of the gel. Typically,\nuntreated PEDOT:PSS films have conductivities below 1 S cm⁻1, and PEDOT:PSS hydrogels\ngenerally fall below 0.1 S cm⁻¹. In this work, the reported values, when combined with the impedance\ndata, appear abnormally high and are not adequately justified.\nAuthors’ Response: We sincerely appreciate you for valuable feedback.\nThis matter has drawn our serious attention. Initially, we had no reason to doubt the reported\nconductivity of PIEgels, as many gels with excellent conductivity—often in the range of tens to\nhundreds of S cm‒1—have been documented in the literature. However, upon recognizing the ion-\ndominated nature of the conduction mechanism, we carried out further verification. Multiple\n17 / 27\nindependent batches of samples were prepared and tested, which consistently showed conductivity\nvalues significantly lower than those initially reported. We identified that the first batch of samples\nhad been compromised due to suboptimal storage conditions. To ensure accuracy, we conducted\nlarge-scale validation using both the four-point probe method and electrochemical impedance\nspectroscopy.\n(1) EIS measurements. As demonstrated in Figure R8, representative replicate electrochemical\nimpedance spectroscopy (EIS) measurements were conducted on 20PP-DNE.\nFigure R8. (A, C and E) Representative Nyquist plots of 20PP–DNE. These symbols are measured experimentally,\nand dashed lines are obtained by fitting using an equivalent circuit model. (B, D and F) Representative Bode plots\nwith impedance and phase angle of 20PP–DNE.\n(2) Four-point probe method. The four-terminal four-pin measurements indicated a bulk electrical\nconductivity of approximately 0.1639 S cm‒1 for PIEgels, while the electrochemical impedance\nsimulations also yielded an ionic conductivity of around 0.0038 S cm‒1. Based on these results, we\n18 / 27\nhave corrected the reported electrical conductivity in Figure 1F.\nAlthough the electrochemical impedance method remains a valid approach for estimating ionic\nconductivity, it is important to note that the values it provides differ in nature from those obtained via\nfour-point probe measurements, which reflect electronic conduction characteristics. These two are\nnot equivalent, as follow Table R1.\nTable R1. Electrical conductivity measured using the four-point probe method and ionic conductivity\nderived from Equivalent circuit fitting.\nConductivity\nMethod Mean  SD Explanation\n(S cm‒1)\n0.1933\n0.1909\n0.1704\nIntrinsic\nFour-terminal\n0.1639  0.0276\nfour-pin method\nElectrical conduction\n0.1566\n0.1527\n0.1193\n0.003758\nEquivalent circuit\nElectrochemical systems\nfitting\n0.004116 0.0038  0.00029\nIonic conduction\n(σ = L/SR)\n0.0035326\nEquivalent circuit fitting of electrochemical impedance spectroscopy (EIS) data was utilized for\nconductivity analysis—a well-established methodology extensively validated across diverse ionic\nmaterials. This technique was selected for its efficacy in decoupling the relative contributions of ionic\nand electronic resistances within mixed ionic-electronic conductors. Analysis revealed that the\neutectogel exhibits lower ionic resistance, a characteristic likely underpinning its superior piezoionic\nperformance.\nWe also made the corresponding changes in the section Molecular and structural design of\nmechanically robust conductive PIEgels, Ionic transport resistance and ion-electron coupling of\nPIEgels, Figure 1 and Figure 3 in the Revised manuscript, marked with red color.\n19 / 27\nComment 8. The manuscript also fails to clarify the ion conduction path under mechanical stress\nwithin the device. The current structure does not appear to constitute a piezoionic device with a proper\nseries electrical configuration. Unfortunately, the authors’ reply does not address the question and\nleaves the core concern unresolved.\nAuthors’ Response: We appreciate your insightful suggestions. The cascaded PIEgels device was\nconstructed by encapsulating six individual PIEgel units within a PDMS mold. Electrical\ninterconnection was achieved by attaching wires to the backside of each unit using conductive copper\ntape, ensuring reliable signal collection. As shown in Figures R9 and R10, the series effect was\nunequivocally demonstrated through piezovoltage measurements. Whereas a single PIEgel unit\ngenerated a peak piezovoltage of 40 mV, the cascaded device produced a peak output ranging from\n200 to 300 mV, demonstrating a clear cumulative effect consistent with voltage summation.\nFigure R9. The cascaded PIEgels device services a self-powered machine for monitoring force stimulations and\ngenerating power.\n20 / 27\nFigure R10. Piezovoltage transient output responding to instantaneous stimulation for the dropping of (A) 10N,\n(B) 20N and (C) 30N in the cascaded PIEgels. Pressure region covers the cascaded PIEgels, with generated\npiezovoltage of approximately 200 mV, 300 mV and 300mV, respectively, confirming the successful series\nconnection of the cascaded PIEgels.\n21 / 27\n Reviewer #3:\nIn the manuscript, the authors developed a mechanically robust and mixed ionic-electronic conductive\neutectogels for continuous piezoionicity. They balance the trade-off between robust mechanical\nproperties and high piezoionic voltage output through hierarchical structure design and charge\ncompensation mechanism. Some minor points need to be addressed before publication.\nWe greatly appreciate your meticulous review and intriguing comments, which has helped us to\nfurther improve our manuscript and research value.\nComment 1. According to the \"charge compensation mechanism\" stated in the manuscript, why do\nthe chloride ions bind to PEDOT when pressure is applied, and when the pressure is removed, the\nsodium ions interact with the PSS to prolong its inactivation time? The authors should provide more\nexplanation about how the pressure influences the ion-chain interactions.\nAuthors’ Response: Thank you for your insightful comment on this aspect and we completely agree,\nand thank you for reminding us. In previous studies, charge compensation between PEDOT:PSS and\ninorganic salt ions has been documented. As follow: Lyu D, et al. Operando NMR electrochemical\ngating studies of ion dynamics in PEDOT:PSS. Nat. Mater. 22, 746-753 (2023). In this work, we\nfurther validate the charge compensation mechanism through molecular and structural perspectives.\nMolecularly, we performed DFT calculations that revealed strong bonding interactions between\nPEDOT and Cl− (‒142.7 kJ mol‒1), as well as between PSS and Na+ (‒309.1 kJ mol‒1). In contrast,\nthe bonding energies of PEDOT‒Na and PSS‒Cl are only as low as ‒36.4 kJ mol‒1 and ‒37.9 kJ mol‒\n1, respectively. These computational results demonstrate the existence of a robust charge\ncompensation via the ion-exchange reaction between NaCl and PEDOT:PSS (Figure 5D to 5F in\nRevised Manuscript).\nFurther explorations of structure transitions using Raman spectroscopy provide solid evidence for\ninvestigating the conformational transitions of PEDOT from a benzenoid structure (disordered coil\nconformation) to a quinoid structure (ordered linear conformation) before and after applying pressure\n(Figure 5G and 5H in Revised Manuscript). Additionally, XPS analysis reveals a significant increase\nin the binding energy of Na+ and Cl− ions under applied pressure, demonstrating the electron transport\nchain propagation via ion-exchange reactions. Collectively, these findings indicate that the ion-\nelectron coupling effect enables dynamic charge compensation via ion exchange between\nPEDOT:PSS and Na+/Cl−, while simultaneously boosting the pressure-driven ion activation and\ninactivation kinetics (Figure 5I and 5G in Revised Manuscript).\nImportantly, we have successfully performed molecular dynamics (MD) simulations to investigate\nthe dynamic migration of Na+ and Cl− during both the application and release of pressure. The\nsimulations reveal that applied pressure induces differential ion migration, during which Na+ exhibits\na higher diffusion coefficient than Cl−, and Cl− is notably confined by the polymer chains. In contrast,\n22 / 27\nupon pressure release, Cl− demonstrates a higher diffusion coefficient compared to Na+, suggesting\nthat Na⁺ becomes further constrained by the polymer matrix. Another critical contribution is charge\ncompensation arising from ion-exchange reactions, therefore, we performed MD simulations with\nvarying numbers of NaCl to probe reaction kinetics. As the number of NaCl molecules increased from\n30 to 60, Na+ and Cl− ions migrate simultaneously, yet temporally alternating mobility, resulting in a\npartial offset of their opposing contributions. These simulation results indicate a kinetically\nunfavorable ion-exchange reactions due to the increased ion number, thereby disrupting the charge\ncompensation mechanism. Based on the above findings, we therefore propose that chloride ions are\nretained by the PEDOT domains upon applied pressure, whereas upon pressure release, sodium ions\ninteract with the PSS-rich regions, thereby prolonging the recovery time.\nWe also made the corresponding changes in the section Piezoionic diffusion kinetics via molecular\ndynamics simulation, Discussion and Figure 6 in the Revised manuscript, as well as Supplementary\nFig. 36 to 38, marked with red color. Figure 6 is as follows:\n23 / 27\nComment 2. In addition, is the longer inactivation time a good thing for pressure sensing? Can it be\nused for memory functions similar to synapses?\nAuthors’ Response: Thank you for your valuable suggestions and positive feedback.\nThis comment represents an insightful perspective. This study provides a valuable perspective on the\nregulation of inactivation time in piezoionic sensing. We argue that tailoring the inactivation time\nmust be closely aligned with the intended application scenario. Specifically, whereas piezoionic\nmaterials generally require high mechanical responsiveness—manifested as a short response time to\nenable real-time conversion of pressure into ionic current—the control of inactivation time follows a\ndifferent principle: a longer inactivation time supports sustained piezovoltage output over brief\nperiods, corresponding to persistent stimulus response; conversely, a shorter inactivation time results\nin transient signals that decay rapidly upon pressure removal. Such sustained output may be\nparticularly beneficial in neuromodulation applications, whereas transient electrical signals may be\nbetter suited for applications such as pressure sensing or synaptic memory, where accurate tracking\nof stimulus dynamics is critical. Therefore, the optimal inactivation profile should be application‐\nspecifically designed, balancing between persistence and transient response based on functional\nrequirements.\nComment 3. The ionic conductivity of eutectogel is 29.09 S/cm, which is much higher than the\nreported ionic conductive gels (below 0.1 S/cm). And this number is calculated from equivalent\ncircuit analysis, is it reasonable?\nAuthors’ Response: Thank you for your valuable suggestions and positive feedback.\nThis matter has drawn our serious attention. Initially, we had no reason to doubt the reported\nconductivity of PIEgels, as many gels with excellent conductivity—often in the range of tens to\nhundreds of S cm‒1—have been documented in the literature. However, upon recognizing the ion-\ndominated nature of the conduction mechanism, we carried out further verification. Multiple\nindependent batches of samples were prepared and tested, which consistently showed conductivity\nvalues significantly lower than those initially reported. We identified that the first batch of samples\nhad been compromised due to suboptimal storage conditions.\nAs demonstrated in Figure R8, representative replicate electrochemical impedance spectroscopy (EIS)\nmeasurements were conducted on 20PP-DNE.\n24 / 27\nFigure R8. (A, C and E) Representative Nyquist plots of 20PP–DNE. These symbols are measured experimentally,\nand dashed lines are obtained by fitting using an equivalent circuit model. (B, D and F) Representative Bode plots\nwith impedance and phase angle of 20PP–DNE.\nTo ensure accuracy, we conducted large-scale validation using both the four-point probe method and\nelectrochemical impedance spectroscopy. The four-terminal four-pin measurements indicated a bulk\nelectrical conductivity of approximately 0.1639 S cm‒1 for PIEgels, while the electrochemical\nimpedance simulations also yielded an ionic conductivity of around 0.0038 S cm‒1. Based on these\nresults, we have corrected the reported electrical conductivity in Figure 1F.\nAlthough the electrochemical impedance method remains a valid approach for estimating ionic\nconductivity, it is important to note that the values it provides differ in nature from those obtained via\nfour-point probe measurements, which reflect electronic conduction characteristics. These two are\nnot equivalent, as follow Table R1.\nTable R1. Electrical conductivity measured using the four-point probe method and ionic conductivity\n25 / 27\nderived from Equivalent circuit fitting.\nConductivity\nMethod Mean  SD Explanation\n(S cm‒1)\n0.1933\n0.1909\n0.1704\nIntrinsic\nFour-terminal\n0.1639  0.0276\nfour-pin method\nElectrical conduction\n0.1566\n0.1527\n0.1193\n0.003758\nEquivalent circuit\nElectrochemical systems\nfitting\n0.004116 0.0038  0.00029\nIonic conduction\n(σ = L/SR)\n0.0035326\nEquivalent circuit fitting of electrochemical impedance spectroscopy (EIS) data was utilized for\nconductivity analysis—a well-established methodology extensively validated across diverse ionic\nmaterials. This technique was selected for its efficacy in decoupling the relative contributions of ionic\nand electronic resistances within mixed ionic-electronic conductors. Analysis revealed that the\neutectogel exhibits lower ionic resistance, a characteristic likely underpinning its superior piezoionic\nperformance. Here are some works related to electrochemical fitting:\n(Ref. 1) Li, T., Qi, H., Zhao, C. et al. Robust skin-integrated conductive biogel for high-fidelity\ndetection under mechanical stress. Nat. Commun. 2025, 16, 88. https://doi.org/10.1038/s41467-024-\n55417-1.\n(Ref. 2) X. Liu, X. Ji, R. Zhu, J. Gu, J. Liang, A Microphase-Separated Design toward an All-Round\nIonic Hydrogel with Discriminable and Anti-Disturbance Multisensory Functions. Adv. Mater. 2024,\n36, 2309508. https://doi.org/10.1002/adma.202309508.\n(Ref. 3) Tian Li, Haobo Qi, Yijing Zhao et al., Robust and sensitive conductive nanocomposite\nhydrogel with bridge cross-linking–dominated hierarchical structural design. Sci. Adv. 2024, 10,\neadk6643. https://www.science.org/doi/10.1126/sciadv.adk6643.\n26 / 27\nWe also made the corresponding changes in the section Molecular and structural design of\nmechanically robust conductive PIEgels, Ionic transport resistance and ion-electron coupling of\nPIEgels, Figure 1 and Figure 3 in the Revised manuscript, marked with red color.\nComment 4. In Figure 1G, why it takes several seconds to reach peak piezovoltage, which is contrary\nto the fast response time (0.02 s) in Figure 4D?\nAuthors’ Response: We appreciate your insightful suggestions. This discrepancy arises from\ndifferences in the frequency and duration of the applied force stimuli.\nIn Fig. 1G, mechanical force was applied three times within one second (Supplementary Fig. 3 in the\nrevised Supplementary Information). Conversely, in Fig. 4, force was applied once every three\nseconds (Supplementary Fig. 18 in the revised Supplementary Information). Fig. 1G characterizes\nthe continuous piezoionic response, hence employing a higher stimulation frequency. Critically, this\nprotocol ensured that subsequent stimuli were applied before the piezovoltage from the preceding\nstimulus had fully decayed. In contrast, Fig. 4 was designed to analyze the response profile and\ninactivation time of individual transient peaks, necessitating a lower stimulation frequency.\nConsequently, stimuli were applied only after the piezovoltage from the previous stimulus had\ncompletely subsided.\n27 / 27"}, {"round": 3, "reviewer_comments": {"reviewer_2": "The authors have addressed my previous comments adquately.", "reviewer_3": "In my view, the innovation of this paper reflects in its investigation of the mechanism of piezoionic materials and the conferral of robust mechanical properties to this material. Through hierarchical structural design, the system enables sustained ion flow under compression. The authors provide an in-depth explanation of the ion steaming and charge compensation mechanism within this ionic-electronic conductive eutectogels through experimental observation and theoretical analysis, offering a strategy for regulating the mechanical properties of piezoionic materials. While the practical application advantages of this material warrant further discussion, the field holds significant potential. Overall, the revised manuscript fully incorporates the reviewers' suggestions. Therefore, the reviewer believes that this manuscript is qualified enough to be published in Nature Communications."}, "author_response": "Point-by-Point Response to Reviewers' Comments\nDear Reviewers:\nWe deeply appreciate your time and effort in reviewing our manuscript and providing constructive\nfeedback on our manuscript entitled “Continuous piezoionicity-driven electromechanical coupling in\nmechanically robust conductive eutectogels (NCOMMS-25-18534B)”. Thank you very much for the\nencouraging comments that help to strengthen the quality of our manuscript. We sincerely hope that\nthe revised manuscript now meets the standards for publication.\nThank you very much for your help in improving this research. Thank you for your kind consideration!\nIn this response letter below,\n Response to Reviewer #2: Page 2\n Response to Reviewer #3: Page 3\nPlease note that:\n Reviewers' comments are in blue color.\n Authors’ responses are in black color.\n1 / 3\n Reviewer #2:\nComment 1A. The authors have addressed my previous comments adquately.\nAuthors’ Response: We greatly appreciate your meticulous review and intriguing comments, which\nhas helped us to further improve our manuscript and research value.\n2 / 3\n Reviewer #3:\nComment 1. In my view, the innovation of this paper reflects in its investigation of the mechanism\nof piezoionic materials and the conferral of robust mechanical properties to this material. Through\nhierarchical structural design, the system enables sustained ion flow under compression. The authors\nprovide an in-depth explanation of the ion steaming and charge compensation mechanism within this\nionic-electronic conductive eutectogels through experimental observation and theoretical analysis,\noffering a strategy for regulating the mechanical properties of piezoionic materials. While the\npractical application advantages of this material warrant further discussion, the field holds significant\npotential. Overall, the revised manuscript fully incorporates the reviewers' suggestions. Therefore,\nthe reviewer believes that this manuscript is qualified enough to be published in Nature\nCommunications.\nAuthors’ Response: We are deeply grateful for the constructive input you provided on our research.\nYour insights have greatly elevated the quality of the manuscript. As you rightly pointed out, we aim\nfor this work to be inspirational, hoping to contribute perspectives and approaches to the future design\nparadigms of flexible bioelectronic devices.\n3 / 3"}]

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