Strain-enhanced stretchable molecular ferroelectric acoustic fibers

Domain: physics
Published: 2026-04-09
Editorial outcome: major_revision

Abstract
Molecular ferroelectrics—hybrid organic-inorga nic architectures that exhibit piezoelectric
coefficients comparable to classic oxide ceramics while offering rich compositional and structural
tunability—have emerged as promising materials for human-interfaced high-frequency acoustic
sensing. Nevertheless, the inherent brittleness and relatively high modulus hinder their practical
deployment on dynamically deformable interfaces. Here, we report stretchable molecular
ferroelectric acoustic fibers fabricated by incorporating molecular ferroelectric
trimethylchloromethyl ammTonium trichlorocadmium (TMCM-CdCl
3
) crystals into flexible
thermoplastic polyurethaRne (TPU) via electrospinning. Intermolecular interactions between
TMCM-CdCl and TPAU, along with the interlocked layered architecture between electrodes and
3
fibers, endow the fiber acoustic sensor with high stretchability (tensile strain >100%), high force
sensing sensitivity (4.36 V/kPa), and wide-frequency acoustic sensing (30–5000 Hz). Crucially, a
strain-induced sensitivity enhancement effect is proposed and verified, where the acoustic
sensitivity of the sensor increases from 15.03 mV/dB to 30.16 mV/dB under strain. Furthermore,
we demonstrate that the acoustic fiber can maintain a high speech recognition accuracy (97.05%)
even for mixed speech data obtained using the acoustic fiber in original and 20% tensile strain
states. This work establishes a route for acoustic sensing at dynamic deformable interface and
advances human-interfaced acoustic applications such as robotic interaction, biomedical
engineering, and virtual reality.

Introduction
Sound is ubiquitous in both natural phenomena and human activities, serving as a fundamental
medium for human perception and environmental interaction. Flexible acoustic sensors emulate
this biological function by converting ambient acoustic information into quantifiable electrical
signals (1-3). Compared with conventional rigid devices, their intrinsic flexibility enables both
conformal skin attachment and adaptability to dynamically curved surfaces (4). These devices have
emerged as a focal point of research due to their transformative potential in robotic interaction (5,
6), biomedicine (7, 8), and virtual reality applications (9, 10).

With advances in material science and sensing technologies, various flexible acoustic sensors,
based on the mechanisms of electromagnetic (11), piezoresistive (12), piezocapacitive (13), optical
(14), triboelectric (5), and piezoelectric (15), have been explored for acoustic perception and
intelligent applications. For instance, Yan et al. utilized barium titanate (BTO)/poly(vinylidene
fluoride-co-trifluoroethylene) piezoelectric fibers woven into a conformable acoustic fabric (16).
This smart fabric enables acoustic pulse direction detection and bidirectional acoustic
communication. As applications evolve from requiring simple, flexible scenarios to those
demanding integration with complex, dynamically deforming surfaces or environments (e.g.,
human body interfaces, typically exhibiting >10N% strain), the development of stretchable acoustic
sensors has therefore become imperative (17)I. However, due to fundamental limitations in device
architecture and working principles, Eexisting acoustic sensors (such as piezoresistive and
piezocapacitive types) often require Lcomplex structural designs to achieve real-time acoustic
sensing under dynamic strain. ICn contrast, piezoelectric acoustic sensors rely on thin-film
vibrations induced by acousticI waves for sound detection. This simple yet efficient working
mechanism provides a feasible route toward stretchable acoustic devices (18).

Conventional piezoelectric materials often suffer from a trade-off between electrical performance
and mechanical properties. Inorganic piezoelectric ceramics, represented by PZT and BTO, exhibit
relatively high piezoelectric coefficients (d ) but are limited by excessive rigidity and complicated
33
fabrication processes (19). On the other hand, organic piezoelectric polymers such as PVDF offer
good flexibility, yet their d remain relatively low (20). Molecular ferroelectrics, as a novel class
33
of piezoelectric materials, have garnered significant attention in recent years owing to their
attractive merits, including structurally tunable frameworks, light weight, low acoustic impedance,
and facile crystallization and film formation (21-23). Taking hybrid organic-inorganic perovskite
molecular ferroelectrics as an example, their piezoelectric behavior originates from the ordered
arrangement and interactions of molecular components (e.g., organic cations and inorganic
frameworks) within the crystal lattice (24). These materials combine the advantageous
characteristics of both organic molecules and inorganic frameworks. It is noteworthy that the d
33
values of certain molecular ferroelectric materials have already surpassed those of traditional
inorganic ceramics (25). For example, our group previously reported the hybrid perovskite
organic-inorganic perovskite molecular ferroelectric TMCM-CdCl (TMCM =
3
trimethylchloromethyl ammonium [Me NCH Cl]+) which exhibits a remarkably high d value of
3 2 33
220 pC/N (26). However, it also faces intrinsic brittleness, typically requiring doping strategies to
enable its application in flexible sensors. Compared with inorganic piezoelectric ceramics,
TMCM-CdCl can be mutually dissolved with polymer matrices in solvents. Furthermore, its
3
abundant organic components allow for the formation of strong intermolecular interactions, such
as hydrogen bonds, ionic bonds, halogen interactions and other van der Waals forces, with the
polymer matrix (27, 28). Consequently, uniformly dispersed TMCM-CdCl crystallites can form
3
robust interfacial bonding with the polymer matrix, making them less prone to fatigue fracture
under strain while enabling efficient stress transmission for electromechanical transduction. Based
on this composite strategy, significant progress has been made in existing research. For example,
the use of a porous TPU framework loaded with TMCM-CdCl crystals has yielded piezoelectric
3
composite materials with high power output (29). Additionally, TMCM-CdCl /PVP composite
3
fibers prepared via the electrospinning process have been successfully applied in low-frequency
sound recognition (30). These studies have confirmed the application potential of the TMCM-
CdCl and polymer composite system. However, the electromechanical coupling behavior of
3
molecular ferroelectric crystals and polymer matrices under dynamic tensile deformation remains
unexplored, and its underlying mechanisms are still unclear. Furthermore, the interface contact
issues between the composite material and elecNtrodes during dynamic deformation have not yet
been considered.

Herein, we designed stretchable TMECM-CdCl
3
/TPU (TCCT) composite fibers by uniformly
dispersing high-d TMCM-CdCl crLystals into a TPU matrix via electrospinning technology,
33 3
which serves as the piezoelectricC active layer. Utilizing the robust intermolecular interactions
between the crystals and the maItrix effectively improved the mechanical tensile stability of the
fibers. In the sensor architecture, we constructed a dense intermediate layer (interlocked layered
architecture) at the interface between the liquid metal (LM)/TPU electrode and the TCCT fibers
through rational process design. This structure not only ensures a robust connection between the
piezoelectric active layer and the electrodes but also effectively enhances the charge coupling
efficiency of the electrodes. The resulting TCCT sensor demonstrated a pressure sensitivity (4.36
V/kPa) and strain performance (109%). For acoustic sensing, the sound sensitivity of the sensor
under stretched conditions increased to 30.16 mV/dB, twice that in the unstretched state. This
improvement primarily originates from the synergistic effect between the strain-induced intrinsic
piezoelectric enhancement of the crystals and the increased stress transfer efficiency resulting from
the densified fiber network. Notably, stretching enhances the sensor’s ability to recognize
information features within the raw speech signal. Overall, the TCCT sensor with strain-enhanced
perception capability provides a viable strategy for developing next-generation flexible acoustic
sensing devices. These devices can adapt to dynamic and complex environments while maintaining
high sensitivity and stability.

Results
To address the brittleness and inflexibility of molecular ferroelectrics and thereby render the
resulting devices compatible with a broad range of complex working scenarios, we incorporated
TMCM-CdCl crystals into a TPU matrix and fabricated TMCM-CdCl /TPU (TCCT) composite
3 3
fibers as the piezoelectric active layer via electrospinning (Fig. 1a). Multiple molecular
interactions formed between the TMCM-CdCl crystals and TPU, including monopolar
3
interactions and van der Waals forces between the -CH groups, -C=O groups in TPU chains and
3
Cl atoms in [CdCl ]− (27), and halogen bonds and abundant van der Waals forces between Cl atoms
3
in [TMCM]+ ([Me NCH Cl]+) and Cl atoms in [CdCl ]− (31). Moreover, the electrospinning
3 2 3
process simultaneously induces a directional poling alignment between TMCM-CdCl and TPU
3
via the applied high-voltage electric field. These molecular interactions promote strong interfacial
adhesion between TMCM-CdCl and the TPU matrix, ensuring the overall tensile stability of the
3
TCCT fibers.

The electrodes employed stretchable LM/TPU composite polymer as the material. The electrode
solution was spread onto a flat-plate collector, enabling the simultaneous one-side electrode
assembly during the fabrication of the piezoelectric active layer. The assembled bilayer structure
was then placed onto the electrode solution, following slow curing, ultimately formed the complete
sensor with top and bottom electrodes (Fig. 1b). Detailed fabrication procedures are provided in
the Methods. The assembled TCCT sensor features a five-layer architecture, comprising
symmetrically arranged upper and lower porouNs layers, dense intermediate layers and a central
nanofiber layer. During electrode curing anId electrospinning formation, a tightly interlocked
structure develops between the piezoeleEctric nanofiber layer and the porous electrode layer. This
architecture significantly enhances inLterfacial bonding between these layers, ensuring reliable
electrical contact during device strCetching (32).

The pressure-sensing capabilityI of the TCCT sensor is enabled by its core filler, TMCM-CdCl
3
crystals. Under external stress, deformation of the TPU matrix effectively couples to that of the
TMCM-CdCl crystallites, and the compressive deformation of the inorganic [CdCl ]− anionic
3 3
framework induces polarization rotation in the organic [TMCM]+ cations, generating a pronounced
piezoelectric response (Fig. 1c) (33). The authentic crystal structure of the paraelectric phase and
configurations of different polarization orientations are shown in Supplementary Fig. 1b.
Synergistically combining the high d coefficient molecular ferroelectric material with a
33
stretchable polymer matrix confers exceptional electromechanical response capability and
stretchability to the TCCT sensor. Remarkably, applied strain significantly enhances the sensor’s
acoustic-vibrational sensitivity, demonstrating pronounced advantages for voice recognition
applications (Fig. 1d).

Fabrication and characterization of TCCT fibers
To achieve stretchable piezoelectric active layer with high performance, we selected the hybrid
perovskite organic-inorganic molecular ferroelectric TMCM-CdCl crystals as the functional filler,
3
which exhibit a large d value of 220 pC/N (Supplementary note 1). Its crystal structure is shown
33
in Fig. 2a. The structure comprises organic cations [TMCM]+ and an inorganic anionic framework
[CdCl ]− formed by CdCl octahedral units (26). Alternating stacking of the [TMCM]+ cations and
3 6
[CdCl ]− anions forms a typical hexagonal hybrid organic-inorganic ABX -type perovskite
3 3
structure. The synthesized TMCM-CdCl crystals and TPU were co-dissolved in N, N-
3
dimethylformamide (DMF) under magnetic stirring for 6 h to obtain a homogeneous
electrospinning solution. During electrospinning, a 20 kV DC electric field was applied between
the needle tip and the flat-plate collector. To characterize the elastic properties of the resulting
composite fibers, atomic force microscopy (AFM) was employed to analyze fiber morphology and
modulus variations before and after doping (Fig. 2b, c and Supplementary Fig. 2). Compared with
pure TPU fibers, the TCCT nanofibers exhibited relatively rough surfaces, with Young’s modulus
increasing from 235 MPa to 290 MPa. Scanning electron microscopy (SEM) observations of fiber
morphology revealed uniform surfaces with embedded white crystalline grains, indicating well-
defined fibrous structures (Fig. 2d). Energy-dispersive spectroscopy (EDS) confirmed the
homogeneous distribution of elements C and Cl throughout the fiber matrix, which represents a
characteristic signature of the TMCM-CdCl crystals. The TCCT fibers exhibited diameters of
3
406.3 ± 30 nm with fibers’ thickness as low as 70 μm (Fig. 2e, f and Supplementary Fig. 3). X-ray
diffraction (XRD) analysis confirmed matching diffraction peaks between the TMCM-CdCl /TPU
3
composite fibers and pure TMCM-CdCl crystals, indicating successful integration of the crystals
3
into the TPU nanofibers (Fig. 2g). Furthermore, Ncomparative analysis of the Raman spectra of TPU
fibers, TCCT fibers, and TMCM-CdCl crysItals reveals that Cl‑related vibrational features are
3
present only in the pure crystal and the TECCT composite fibers, as shown in Supplementary Fig.
4 and its expanded view of the 760–8L60 cm-1 region (Fig. 2h). Fourier transform infrared (FTIR)
spectroscopy demonstrated an enChanced characteristic peak in the 700–800 cm-1 range, which
further confirmed the introductioIn of the C-Cl structure (Supplementary Fig. 5). Given the second-
harmonic generation (SHG)-inactive nature of the TPU matrix and the noncentrosymmetric
structure of TMCM-CdCl , we performed SHG experiments to examine the polarization
A3
characteristics of the composite fibers. A femtosecond laser source at 800 nm was used to excite
the TCCT fibers, the output SHG signals with a peak wavelength at 400 nm were collected (inset,
Fig. 2i). As shown in Fig. 2i, significant SHG response was observed in the TCCT fibers compared
to TPU fibers, attributable to the presence of TMCM-CdCl ’s noncentrosymmetric crystalline
3
structure. The ferroelectric piezoelectric properties of the TCCT fibers were characterized by
Piezoresponse Force Microscopy (PFM). The selected fiber morphology is shown in
Supplementary Fig. 6. The typical in-plane and out-of-plane PFM amplitude and phase images
showed distinct domain structure distributions in the two modes, confirming the presence of
spontaneous polarization in the fibers. The differences between in-plane and out-of-plane
components corresponded to the multipolar axis characteristics of TMCM-CdCl (Supplementary
3
Fig. 7). Meanwhile, the difference in phase imaging before and after the application of voltage also
confirmed the presence of ferroelectricity. Under the electric field, the dependence of amplitude
and phase on voltage displayed typical butterfly and hysteresis loops, respectively, offering
compelling quantitative evidence for polarization switching and hysteresis behaviors of
ferroelectric polarization (Supplementary Fig. 8). Although bulk TMCM-CdCl crystals exhibit
3
limited flexibility that restricts their practical applications in flexible, soft, and implantable devices,
embedding these crystals within a soft TPU matrix significantly enhanced mechanical compliance
while imparting stretchability. Fig. 2j demonstrates the TCCT fibers undergoing intentional
repeated bending, stretching, folding, and twisting, highlighting its exceptional flexibility and
mechanical robustness. The electrospun TCCT fibers exhibited exceptional stretchability and
maintain mechanical durability even after 1000 stretch- release cycles at 70% strain
(Supplementary Fig. 9). Higher TMCM-CdCl crystals loading occupied space within the TPU
3
elastic nanofibers and disrupts inter-fiber connections, decreasing the maximum strain from 141%
at 1% content to 53% at 15% content (Fig. 2k).

Fabrication and characterization of TCCT sensor
To achieve full sensor stretchability, we engineered stretchable electrodes by blending LM
conductive fillers with a polymer matrix. The LM/TPU electrodes exhibit negligible resistance
change under 200% strain (Supplementary Fig. 10). The TCCT sensor features a sandwich
structure (Fig. 3a, b), comprising two LM/TPU electrodes encapsulating a TCCT fibers. The
porous LM/TPU layers function dually as both conductive electrodes and flexible supporting
substrates. The cross-section EDS mapping (SuNpplementary Fig. 11) identified the middle layer as
TCCT fibers, and the main element is Cl. CrIoss-sectional SEM and optical images revealed the
device architecture (Fig. 3c and SupplemEentary Fig. 12), where an interlocked intermediate layer
formed between the electrodes and pLiezoelectric active layer. This integrated structure ensures
effective electrode-to-active-layerC contact under tensile strain. The mechanical properties of the
TCCT sensor were evidenced bIy cyclic stretch-release curves at varying strains and repeated
stretch-release testing at 50% strain (Fig. 3d and Supplementary Fig. 13). Compared with the 1wt%
TCCT fibers, the TCCT fibers with LM/TPU electrodes exhibited higher tensile fracture strain. To
further investigate the strain behavior of TCCT fibers, we fabricated sensor with only a single-
sided electrode. Under progressively increasing strain, the white TCCT fibers maintained
conformal contact with the gray LM/TPU electrode. Upon reaching the fracture limit, the fibers
ruptured while the remaining segments retained strong adhesion to the electrode surface
(Supplementary Fig. 14). Simultaneously, real-time visualization under optical microscopy
confirmed intact interfacial bonding in TCCT sensor during stretching (0–40% strain), with no
observable interfacial delamination (Fig. 3e and Supplementary movie 1). We then established a
mechano-electrical measurement system and implemented multi-layer encapsulation to minimize
interference from triboelectric on piezoelectric voltage during testing (Supplementary Fig. 15) (34).
The role of TMCM-CdCl crystals in the mechano-electrical response characteristics of sensor was
3
systematically studied. At a pressure of 1 kPa, the TCCT fibers showed obvious piezoelectric
response, while the pure TPU fibers produced no voltage output (Supplementary Fig. 16). This
confirms the piezoelectricity is solely attributed to the molecular ferroelectrics. Upon altering the
content of TMCM-CdCl crystals, it was observed that the trend of changes in the output voltage
3
and current of the TCCT sensor exhibits an initial increase followed by a decrease. The output
voltage of the TCCT sensor reaches its maximum at a 5% content (Fig. 3g, Supplementary Fig.
17). The d of the TCCT fibers was also measured by linear fitting of charge the charge versus
33
force data. As calculated, 5% TCCT fibers exhibited the maximum d of approximately 32.00
33
pC/N (Supplementary Fig. 18a–e). To achieve a balance between satisfactory electrical output and
mechanical strain capability, we determined the optimal content of TMCM-CdCl to be 5%. At
3
this level, the TCCT fibers exhibited a maximum strain of approximately 109%. We hypothesize
that the initial increase is caused by the gradual increase in TMCM-CdCl content. However, as
3
the content continues to increase, the enhanced conductivity of the precursor solution exacerbates
the instability of the jet (35). Therefore, at concentrations of 10% and 15%, the beads formed due
to jet instability create spot-like dense regions on the fibers surface (10% and 15%)
(Supplementary Fig. 19). EDS analysis indicated a tendency for Cl elements to aggregate at these
defect sites (Supplementary Fig. 20). Such microstructural inhomogeneities caused a non-uniform
distribution of the polarization field, thereby compromising the macroscopic piezoelectric output.
In contrast, the 5 wt% TCCT fibers not only maintained a homogeneous dispersion of Cl elements
but also possessed a significantly higher effective content compared to the 1 wt% and 3 wt%,
ultimately demonstrating the best piezoelectric performance. As shown in Fig. 3g, the TCCT fibers
with LM/TPU electrodes exhibited significanNtly higher output voltages than those with Al
electrodes across different TMCM-CdCl crysItal doping levels. Supplementary Fig. 21 provided a
3
comparative analysis of the voltage andE current output curves for 5 wt% TCCT fibers under the
two electrode configurations. This peLrformance enhancement stems from the tightly interlocked
intermediate layer, which effectiCvely eliminates air gaps between the electrodes layer and
piezoelectric active layer, while iIncreasing the functionally effective contact area (36). Electrospun
membranes, due to their porous nature, are highly prone to air gap formation when laminated with
conventional Al electrodes. Based on kirchhoff laws, we formulate the charge distribution model:
𝑄
△𝑄 = (1)
2
𝐶𝑃(
𝐶𝑎+𝐶𝑝
)
Where C and C denote the air capacitance and piezoelectric active layer capacitance, respectively.
a P
The resulting air gaps introduce additional parasitic capacitance, which consequently reduces
induced charge at the electrodes. In contrast, the LM/TPU electrode design in TCCT sensor
effectively enhances charge collection efficiency by both eliminating interlayer air gaps and
enlarging contact area through its interlocked architecture—thereby significantly improving the
sensor’s electromechanical conversion efficiency (Fig. 3f, Supplementary Fig. 22). Pressure
sensitivity constitutes a critical performance metric for TCCT sensor, defined as the ratio of output
voltage variation (ΔU) to applied pressure change (ΔP) under stable operating conditions. The
sensitivity formula is expressed as S = ΔU/ΔP. As shown in Fig. 3h, within the 0-6 kPa pressure
range, the LM/TPU electrodes configuration achieved a voltage sensitivity of 4.36 V/kPa,
demonstrating significant superiority over conventional Al electrode configuration (see
Supplementary information for calculation details and the data listed in Table 2). Under distinct
pressures (0.5, 1 and 4 kPa), the TCCT sensor generated voltage waveforms with progressively
increasing amplitude while maintaining signal stability (Supplementary Fig. 23). We evaluated the
frequency stability of the TCCT sensor at 1–3 Hz, and the experimental results showed that its
output voltage could maintain stability (Fig. 3i). The TCCT sensor exhibits a response time of
0.03 s, which corresponds to the duration required for the voltage to rise from 10% to 90%
(Supplementary Fig. 24). Durability testing at 0.5 kPa demonstrates preserved waveform integrity
through 7,500 cycles, confirming long-term operational reliability (Supplementary Fig. 25). When
benchmarked against previously reported flexible ferroelectric sensors incorporating inorganic(37),
organic(38-42), and hybrid molecular ferroelectric materials (43, 44) (Fig. 3j, Supplementary
Table 1), the TCCT sensor exhibits exceptional performance in both sensitivity and tensile strain
tolerance. This dual advantage enables precise detection of low-pressure vibrations (e.g., acoustic
signals) and seamless adaptability to stretchable scenarios.

Responses to acoustic forces
Acoustic waves belong to low-pressure vibrational stimuli. To verify the low-pressure detection
capability of the TCCT sensor, we constructed an acoustic testing system (Fig. 4a). In this system,
a sound controller generated sound waves with specific frequency and amplitude, a loudspeaker
served as the sound source, and the data storagNe unit recorded the response voltage generated by
the TCCT sensor. One end of the TCCT sensIor and its lead wire were fixed to a support fixture,
constituting a rigid constraint, while the Eother end was connected to PI tape secured to a fixture on
the opposite side, forming an elasticL constraint (Supplementary Fig. 26). The rigid constraint
suppressed interference from lead Cvibrations during acoustic wave acquisition, whereas the elastic
constraint permited micro-deforImation of the sensor under sound pressure, preserving acoustic
response sensitivity. The sound wave is a sine wave with a defined frequency and decibel level.
Under constant 80 dB pure-tone excitation, the TCCT sensor demonstrated good acoustic response
characteristics across the 30–5000 Hz frequency range (Fig. 4b). Subsequently, we investigated
the influence of strain on the sensor’s acousto-electric conversion capability under an 80 dB and
100 Hz acoustic field (Supplementary Fig. 27). The results showed that the output voltage of the
TCCT sensor continued to increase with strain (0–40% strain), but the rate of voltage rise slowed
significantly once strain exceeded 20%. Therefore, to clearly demonstrate the improvement
resulting from stretching, subsequent experiments focused on the 0–20% strain range. Across
varying acoustic frequencies (30–5000 Hz) and decibel levels (70–100 dB), the TCCT sensor
under 20% strain exhibits significantly superior acoustoelectric conversion capability and acoustic
pressure sensitivity compared with those at 0% and 10% strain (Fig. 4c, d). Original voltage
waveforms are documented in Supplementary Fig. 28 and Fig. 29. Stretching enhances the
sensitivity of the TCCT sensor, which exhibited stable linearity with strain-dependent
enhancement of acoustic sensitivity. Compared with its state before stretching, the acoustic wave
sensitivity of the stretched TCCT sensor increases to 30.16 mV/dB. Fig. 4e elucidates the
mechanism of strain-enhanced piezoelectric response. Under the same acoustic excitation, lateral
stretching induces a certain strain in the TMCM-CdCl crystals within the fibers (Supplementary
3
Fig. 30, with material parameters provided in Table 3), which directly enhances the intrinsic
piezoelectric response of the crystals (45). Simultaneously, it promotes a denser internal structure
of the TCCT fibers (Supplementary Fig. 31). The compact structure improves the mechanical
coupling and stress transfer efficiency between the fibers (46), ensuring that external loads are
more effectively transmitted to the crystals embedded in the TPU matrix. The synergistic effect of
strain-induced enhancement of the intrinsic piezoelectric response of the crystals and improved
stress transfer efficiency resulting from the optimized fiber network structure enhances the
electromechanical conversion efficiency of the TCCT sensor, resulting in a significant increase in
surface charge density and output voltage. Signal-to-noise ratio (SNR), a critical parameter for
assessing output signal quality, is defined as the ratio of useful signal power to background noise
power under specified operating conditions, expressed as SNR = 20log(V /V ). Within the
output noise
0–1.3 Pa sound pressure range, the strained TCCT sensor demonstrated higher SNR values
compared to its unstrained state (Fig. 4f). Benchmarked against state-of-the-art flexible
piezoelectric acoustic sensors (Fig. 4g) (2, 15, 16, 47-51), the TCCT sensor achieves a broader
dynamic detection range (30–5000 Hz) that fully encompasses the human voice frequency
spectrum (300–3400 Hz). Although comparison results indicate that some flexible piezoelectric
acoustic sensors do outperform the current TCCNT sensor in terms of frequency response range, the
TCCT sensor possesses a strain-enhancedI acoustic sensing capability, which validates its
significant advantages for dynamic and dEifferent voice detection applications.

Applications and demonstrationCs
Voice information represents a pIrimary means of human interaction. We simulated the complete
human auditory perception and recognition process by integrating TCCT sensor with deep learning
algorithms (Fig. 5a). The TCCT sensor mimics the human auditory mechanism by converting
external acoustic stimuli into electrical signals. Deep learning algorithms then process the sensor
data, emulating the brain’s capacity to analyze, process, and recognize acoustic signals.
Comparative analysis of the piezoelectric signals acquired by the commercial sensor (LDT0-028K)
and the TCCT sensor during continuous audio playback demonstrated that the TCCT sensor
achieves high fidelity in reconstructing the original waveform (Fig. 5b and Supplementary movie
2). Further time-frequency analysis via short-time Fourier transform (STFT) revealed that the
TCCT sensor completely preserved the complex time-varying frequency characteristics of the
original speech within the 0–2000 Hz range, whereas the commercial sensor exhibited severe
information loss (Fig. 5c). Furthermore, a comparison of the piezoelectric signals collected by the
TCCT sensor before and after stretching revealed a significant increase in output voltage, along
with an improvement in its high-frequency response capability (Supplementary Fig. 32). Fast
Fourier transform (FFT) analysis revealed that the TCCT sensor outperformed commercial sensor
in capturing and reconstructing key frequency components across the 0-1000 Hz spectrum
(Supplementary Fig. 33). Under 20% strain, the sensor enabled partial reconstruction of frequency
components within the 1000–2000 Hz band, albeit with variations in the amplitude ratios of certain
subtle spectral peaks owing to the intrinsic damping of the device. Concurrently, a shift of the peak
response toward higher frequencies was observed. This phenomenon originated from strain-
induced changes in the elastic stiffness of the TCCT sensor, leading to an increase in high-
frequency components (Supplementary note 2). Although the change in stiffness caused by
stretching introduces slight resonance peak shifts, the enhancement in sensitivity plays a decisive
role in improving the spectral consistency with the original signal. Specifically, under 20% strain,
the acoustic response characteristics of the TCCT sensor are enhanced. Compared with the
unstretched state, the stretched sensor can more effectively capture the high-frequency details of
the original sound signal. This strain-enabled rapid frequency response tuning allows
customization of sensitivity ranges for targeted applications, demonstrating exceptional versatility
in acoustic detection.

To evaluate the impact of strain on speech signal feature acquisition by TCCT sensor, we captured
acoustic signals from sensors under before-stretching and after-stretching conditions (Fig. 5d and
Supplementary Fig. 34). We tested words such as Science and Nature, and the TCCT sensor was
able to accurately reconstruct the speech signals without degradation even under stretching
deformation. The strained state exhibited significantly amplified voltage amplitudes while
preserving waveform characteristics with onlyN minor deviations. Simultaneously, we employed
deep learning techniques to classify and reIcognize basic speech elements, utilizing a hybrid
architecture of convolutional neural neEtworks (CNN) and long short-term memory (LSTM)
networks to process the test data (FigL. 5e). Here, the CNN extracts local features of the speech
signal, filters out noise, and capturCes key acoustic patterns effectively. The LSTM is designed for
processing sequential data and cIan model the temporal dependencies in speech. The combination
of CNN and LSTM enhances the robustness of the model in recognizing speech under different
strain conditions. The network employs three one-dimensional convolutional modules (channel
configuration: 128-256-512, kernel size: 5) for local acoustic feature extraction. A bidirectional
LSTM layer (128→64 units) captures temporal dependencies, where the initial 128-unit layer
preserves sequence states and the subsequent 64-unit layer outputs global contextual features. Final
classification is performed through a fully connected layer. Using t-distributed stochastic neighbor
embedding (t-SNE), we visualized TCCT sensor data under varying stretching conditions in a low-
dimensional space. Distinct clustering was observed for signals acquired in the unstretched state
and stretched state (Fig. 5f, Supplementary Fig. 35a). Clear clustering persists when combining
before-stretching and after-stretching data (Fig. 5g). The confusion matrix synthesizes the
classification accuracy, and the recognition accuracy of the mixed data can reach 97.05% (Fig. 5h).
Although the prediction accuracy for the mixed data decreased compared to that in unstretched
and stretched states alone (Fig. 5i and Supplementary Fig. 35b-c), it maintained distinct clustering
and high recognition accuracy. This demonstrates the TCCT sensor’s capability to precisely
reconstruct speech signal features under mechanical stretching.

Methods
Synthesis of TMCM-CdCl crystals
3
All reagents were purchased from commercial suppliers and used without further purification.
Equimolar amounts of trimethylamine (30 wt% in water) and dichloromethane were added to
acetonitrile with stirring for 72 h at ambient temperature. Subsequently, the solvent was removed
under reduced pressure to yield TMCM-Cl. 50 mmol TMCM-Cl and 50 mmol CdCl were
2
dissolved in deionized water, followed by slow evaporation at ambient conditions to form white
single crystals of TMCM-CdCl .
3

Electrospinning TCCT fibers
A TMCM-CdCl solution was prepared by dissolving a measured quantity of TMCM-CdCl
3 3
crystals in 10 mL of DMF (Aladdin, GC grade >99.9%) under continuous heating and stirring at
60°C for 1 h. Subsequently, 1.2 g of TPU was added to the TMCM-CdCl solution. After heating
3
and continuous stirring at 60 °C for 5 h to obtain a transparent spinning solution. The prepared
spinning solution was loaded into a syringe with a metallic needle (Size: No. 19). A voltage of 20
kV was applied to the needle tip with a syringe feed rate of 0.65 mL h-1. The syringe underwent
horizontal reciprocating motion with a travel diNstance of 120 mm at a traverse speed of 10 mm/s.
A flat-plate collector was positioned approximIately 120 mm from the needle to collect deposited
TMCM-CdCl
3
/TPU composite nanofEibers. Fibers’ thickness was tailored by varying
electrospinning duration.

Device fabrication of TCCT seInsor
A TPU solution was prepared by dissolving 3 g TPU in 30 mL of DMF with continuous heating
and stirring at 60 °C for 5 h. Subsequently, 3 g of liquid metal (LM, 75% Ga, 25% In) was added
to the TPU solution. The mixture underwent probe sonication (KC-600W, 75%) in a room-
temperature water bath for 0.5 h to yield a uniformly dispersed LM/TPU electrode composite
solution. Prior to electrospinning the TCCT fibers, a certain amount of (1.0–1.5 mL) the electrode
composite solution was transferred into a pre-fabricated rectangular Excoflex mold (length × width:
60 mm × 30 mm) positioned on the flat-plate collector. The mold was maintained at 40 °C and 50%
relative humidity for 0.25 h to allow surface DMF evaporation. Subsequently, environmental
conditions were adjusted to 40 °C and 20% humidity to initiate the electrospinning process
(parameters as previously described), enabling direct deposition of the TCCT nanofiber membrane
onto the pre-cured electrode layer. Following electrospinning, TCCT fibers with unilateral
LM/TPU electrodes were obtained. The resulting fibers underwent vacuum drying at 40 °C for 12
h. Subsequently, under identical environmental conditions (40 °C, 20% humidity), the electrode
composite solution was maintained for 0.25 h. The TCCT fibers with a unilateral electrode was
overlaid onto the LM/TPU electrode solution and immediately transferred to a fume hood for
ambient drying (2 h). Subsequently, the assembly was sandwiched between parallel plates under
uniform pressure and vacuum-dried at 40°C for 12 h, yielding the final TCCT sensor with bilateral
electrodes.

Measurements and characterization
The phase purities and identification of TMCM-CdCl crystals, TPU fibers, and TCCT fibers were
3
characterized by X-ray diffraction (XRD; Bruker D2 Phaser). Internal microstructure of TCCT
fibers was analyzed using second-harmonic generation (SHG; WITec alpha300R). The
ferroelectricity of the TCCT fibers was characterized using an atomic force microscope (AFM,
Asylum Research MFP‑3D) with an AC drive voltage applied to the conductive tip. Conductive
Pt/Ir-coated silicon probes (EFM-50, Nanoworld) were used for domain imaging and polarization
switching studies, with a nominal spring constant of ~2.8 nN/nm and a free-air resonance
frequency of ~75 kHz. Fiber morphology, fibers thickness, and elemental composition of TCCT
fibers were assessed by scanning electron microscopy (SEM; ZEISS Sigma 360) coupled and
energy-dispersive X-ray spectroscopy (EDS). Topography of individual fibers and Young’s
modulus were determined via atomic force microscopy (AFM; Oxford Asylum Research MFP-
3D). Tensile properties of fibers were evaluated with a universal testing machine (Pubtester TST-
01H). Piezoelectric response signals under varying pressure conditions were acquired using a
digital oscilloscope (Keysight DSOX3024T) aNnd electrometer (Keithley 6514). Sound pressure
levels were measured using a sound level mIeter (AR814) coupled with a reference loudspeaker
(R1080BT).

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "General commeents:\nThe manuscript reports a composite strategy by combining molecular ferroelectric fibers with low-modulus polymer fibers\nthrough electrospinning to overcome brittleness. However, both the strategy and the fabrication technique are rather\nconventional and do not provide a clear breakthrough. Moreover, the work lacks in-depth characterization to elucidate the\ncore mechanism of sensitivity enhancement, leaving key claims insufficiently substantiated. In addition, there are\ninconsistencies in data reporting, contradictions in interpretation, and issues with data presentation that reduce the overall\nclarity and rigor of the study. Taken together, these issues seriously undermine the novelty and reliability of the work, and in\nits current form, the manuscript is not suitable for publication.\nMy specific concerns are outlined below:\n1. There is an inconsistency in the reported sensitivity. The Abstract and the last paragraph of the Introduction state 4.69 V\nkPa⁻¹, whereas the main text and the Conclusion cite 4.36 V kPa⁻¹. This inconsistency reduces clarity and should be\ncorrected and justified.\n2. The claim that TMCM-CdCl3 preserves its molecular ferroelectricity in the TPU composite is unconvincing. While the\nauthors emphasize multiple intermolecular interactions with TPU, such interactions could also disrupt the crystalline\nstructure required for ferroelectricity. This is reflected in Figure 2g, where the original split diffraction peaks merge after\nembedding. Moreover, the SHG signal in Figure 2i is insufficient, as it can result from interfacial polarization or partial dipole\nalignment rather than intrinsic ferroelectricity. Without corroborating evidence (e.g., P-E loops or domain imaging), the\nconclusion is unsupported.\n3. In Figure 2g, the XRD patterns of the TCCT composite clearly show the characteristic diffraction peaks of TMCM-CdCl3,\nconfirming its crystalline presence. However, in Figure 2h, the corresponding FTIR spectrum displays the Cl-related\nvibrational features only very weakly, despite the nominally identical filler content. This inconsistency raises questions about\nthe actual structural and chemical state of TMCM-CdCl₃ in the TPU matrix. The authors should clarify this discrepancy and\nprovide further evidence (e.g., deconvoluted FTIR spectra, Raman analysis).\n4. In Figure 2k, the stress-strain curves show unexpected trends: the modulus at 1 wt% appears higher than at 3 wt%, and\nthe ultimate stress at 10 wt% is similar to 5 wt%. These inconsistencies are counterintuitive, and the authors should clarify\nthe reasons for this behavior.\n5. In Page 8, line 256-257, the authors attribute reduced output at 10 wt% to aggregation and uneven polarization. However,\nthey previously emphasized that strong interactions with TPU ensure uniform dispersion, which is contradictory. At such a\nlow loading, severe aggregation is unlikely, raising doubts about the stability of the ferroelectric polarization within the\ncomposite. The authors should clarify this inconsistency.\n6. In Figure 3g, LM/TPU is the main system, yet the authors provide full loading-dependent data only for Al/TPU, while\nLM/TPU is represented by a single 5 wt% point. Since Al is merely a reference, one dataset would suffice; the\ncomprehensive trend should have been shown for LM/TPU. Please clarify this data selection.\n7. In Figure 3h, the pressure-dependent voltage responses already encompass the information that is later repeated in\nFigure 3i. The latter appears redundant, as it does not add new insights beyond the linear plots. The authors should justify\nthe necessity of Figure 3i or consider moving it to the Supporting Information.\n8. In Figure 4e, the underlying mechanism is explained in Note 2, which attributes the sensitivity enhancement solely to\ncross-sectional reduction and stress increase. This explanation appears highly idealized for an electrospun fibrous mat,\nwhich is porous and anisotropic. The definition of an “effective cross-section” is not straightforward, and stress distribution is\nlikely non-uniform due to fiber orientation and interfacial constraints. Moreover, potential variations in the piezoelectric\ncoefficient (d₃₁) under strain, as well as the trade-off between sensitivity enhancement and frequency shift, are not\naddressed. The authors should provide experimental evidence (e.g., cross-sectional imaging, finite-element simulations, or\npolarization analysis) to support the assumptions behind equations (S5–S8).\n9. In Figures 5b and 5c, the original sound signal and the sensor outputs are visibly different. Supplementary Fig. 19 further\nshows that the original signal has a clear feature at 600-700 Hz, while the TCCT sensor, with or without strain, exhibits only\nweak response in this range. This indicates significant distortion and undermines the claim of faithful sound reproduction.\nThe authors should address this limitation directly.", "reviewer_2": "The scope of the paper entitled \"Strain-Enhanced Stretchable Molecular Ferroelectric Acoustic Fiber\" presents an acoustic\nsensor fabricated through electrospinning technology by integrating molecular ferroelectric crystal TMCM-CdCl3 with\nthermoplastic polyurethane (TPU), demonstrating high stretchability (>100% strain) and piezoelectric response (4.69 V/kPa).\nHowever, the novelty of the material system (TMCM-CdCl3/TPU) and the electrospinning fabrication process should be\nmore clearly stated. The proposed strain-enhancement mechanism needs sufficient experimental evidence and rigorous\nvalidation. The following comments should be addressed by major revision before this paper is suitable for publication in\nNature Communications.\n1. The authors emphasize that the molecular ferroelectric material TMCM-CdCl3 exhibits a high piezoelectric coefficient and\nrich tunability, positioning it as a key solution to the application bottlenecks of traditional piezoelectric materials in flexible\nacoustic sensing. However, composite systems of TMCM-CdCl3 with polymer matrices, including TPU, have been\npreviously reported (Nat. Commun. 2024, 15, 8636), and the device performance has no significant improvements.\nFurthermore, electrospun fibers integrating TMCM-CdCl3 with polymers have been utilized in acoustic sensors (Adv. Mater.\n2025, 37, 24092). The authors must therefore more clearly and forcefully articulate the novelty and distinctiveness of their\nwork relative to these prior studies.\n2. The authors' claim that \"This improvement primarily originates from the strain-induced stress concentration effect\" is\ncurrently supported only by the macroscopic electrical output of the device and a theoretical formulation. To strengthen this\nconclusion, additional experimental evidence is recommended.\n3. The presented cyclic tensile stability tests yield excellent results. However, for practical deployment, the sensor must\nwithstand environmental challenges such as varying temperature and humidity. Specifically, the stability of the water-soluble\nTMCM-CdCl3 component requires thorough investigation, particularly regarding potential dissolution and recrystallization\nunder cyclic humidity conditions and overall performance retention in high-humidity environments.\n4. The authors compare the sensor performance of Al electrodes with LM/TPU electrodes, attributing the inferior\nperformance of the Al electrodes to the formation of an air gap at the interface with the TCCT electrospun film. The rationale\nfor selecting Al as the benchmark for comparison should be explicitly stated. Additionally, to more directly address the air-\ngap issue, a control experiment involving the deposition of Al or other metal electrodes directly onto the TCCT film should be\nconducted, and how about its performance.\n5. The authors repeatedly emphasize the critical role of the interlocked intermediate layer. However, the formation\nmechanism of this layer and its specific interaction with the piezoelectric layer remain unclear. Experimental evidence and\ncharacterization detailing the layer's formation process and interface properties are required to support these claims.\n6. The molecular ferroelectric material TMCM-CdCl3, which possesses a high piezoelectric coefficient (d33 = 220 pC/N),\nwas incorporated into a TPU matrix to fabricate composite fibers. It is crucial to investigate whether this fabrication process\ncompromises its piezoelectric coefficient.\n7. The authors state in both the Introduction and Conclusion that the TCCT fiber exhibits excellent tensile properties, citing a\nmaximum strain of 102%. However, the corresponding tensile data and analysis appear to be absent from the Results and\nDiscussion section.\n8. The authors claim in Figure 4g that the TCCT sensor achieves a wider frequency detection range compared to the current\nstate-of-the-art piezoelectric acoustic sensors. However, the literature survey appears incomplete. Several recent reports on\npiezoelectric acoustic sensors with broad frequency detection ranges appear to have been overlooked (e.g., Nano Energy\n2025, 143, 111312; Adv. Funct. Mater. 2024, 34, 2312699; Nature 2022, 603, 616; Nano Energy 2022, 101, 107610).\n9. The authors investigate the effect of strain on the sensor's acoustoelectric conversion capability, concluding that 20%\nstrain yields the maximum voltage output. This conclusion, however, is based on data from only three strain states (0%,\n10%, and 20%). Whether a higher strain could yield a greater response\n10. The macroscopic deformation of the piezoelectric fiber during stretching will inevitably generate a significant strain-\ninduced electrical signal. Will there be any interaction or interference between this strain-induced signal and the target\nacoustic signal?\n11. The claim that \"under 20% strain, the TCCT sensor exhibits amplified response characteristics at higher frequencies\"\nrequires substantiation. This claim is not convincingly supported by the data presented in Figure 4c, which shows negligible\ndifferences in the high-frequency voltage output across the different strain states. To robustly support this conclusion,\nadditional data characterizing the frequency response under various strain states is essential (e.g., modal analysis).\n12. Visual inspection of Figures 5b and 5c suggests that the piezoelectric signal captured before straining aligns more\nclosely with the original audio waveform and exhibits finer acoustic details compared to the signal after straining. This\nobservation appears to contradict the central claim that strain enhances sensing performance.\n13. Figure 5f and 5g present the data before straining and a mixture of pre- and post-straining data, respectively. However,\nthe dataset corresponding solely to the post-straining state is missing, which is crucial for a direct evaluation of the strain's\neffect. Furthermore, the observed decline in accuracy for the mixed dataset requires a clear explanation.", "reviewer_3": "The manuscript presents stretchable molecular ferroelectric acoustic fibers with strain-enhanced sound perception\ncapabilities. The fibers exhibit exceptional speech recognition capabilities, with enhanced sensitivity as strain increases.\nThis study could be interesting for the audience working on molecular ferroelectrics. I recommend the publication of the\nmanuscript in Nature Communications, while there are some issues have to be addressed first.\n1. The authors used a class of hybrid organic-inorganic molecular perovskite ferroelectrics. Considering the broad\nreadership of Nature Communications, the authors are suggested to add a description in the appropriate place within the\nmain text about the advantages of molecular ferroelectrics when compared to traditional piezoelectric materials like PZT,\nBTO, and PVDF.\n2. The manuscript introduces a molecular ferroelectric composite material prepared by incorporating TMCM-CdCl3 into a\nthermoplastic polyurethane (TPU) matrix. During the spinning process, the electrode layer is assembled to achieve the\nfabrication of a stretchable ferroelectric acoustic device. What are the differences and advantages of the molecular\nferroelectric composite materials and device fabrication method proposed in the manuscript compared to previously reported\npiezoelectric acoustic devices?\n3. The d33 of TMCM-CdCl3 is 220 pC/N. What is the d33 of TPU/TMCM-CdCl3 (TCCT) composite fibers at different\ncontents of TMCM-CdCl3? Are the piezoelectric coefficients measured by electrical resonance method which is\nrecommended by IEEE Standard on Piezoelectricity.\n4. Response time is an important parameter in molecular ferroelectric acoustic fibers. How is the response time of the\npiezoelectric output of the molecular ferroelectric fibers?\n5. Under constant pressure, what is the response trend of the ferroelectric acoustic fibers across different frequencies?\n6. Please explain why this neural network model was chosen to be used over others. Considering the broad multi-\ndisciplinary readers, the author should give the brief necessary background.\n7. Some spelling and format mistakes should be corrected. For example, Line 181 on Page 6, and Line 564 on Page 19. The\nauthors have to carefully check the English throughout the manuscript."}, "author_response": "For your convenience of reading,\nAnswers to the reviewers in blue\nModifications of the manuscript in red\nReview round: 1\nReviewer: 1 The manuscript reports a composite strategy by combining molecular\nferroelectric fibers with low-modulus polymer fibers through electrospinning to\novercome brittleness. However, both the strategy and the fabrication technique are\nrather conventional and do not provide a clear breakthrough. Moreover, the work lacks\nin-depth characterization to elucidate the core mechanism of sensitivity enhancement,\nleaving key claims insufficiently substantiated. In addition, there are inconsistencies in\ndata reporting, contradictions in interpretation, and issues with data presentation that\nreduce the overall clarity and rigor of the study. Taken together, these issues seriously\nundermine the novelty and reliability of the work, and in its current form, the\nmanuscript is not suitable for publication.\nResponse: We would like to thank the reviewer for their insights. We have made the\nfollowing changes that we hope will provide an adequate amount of detail to\ndemonstrate rigor, innovation, and impact:\n1. We conducted a comprehensive review of all data in the manuscript and optimized\nthe presentation of some data to ensure overall clarity and scientific rigor.\n2. We have added a substantial number of supplementary figures to provide deeper\ncharacterization of the material properties and to thoroughly clarify the underlying\nphysical mechanisms.\n3. We have further strengthened the discussion on the innovativeness of the TCCT\nsensor in the manuscript, highlighting the excellent tensile stability achieved through\nrobust interfacial bonding, as well as the strain-enhanced sensitivity performance\ndemonstrated by the sensor.\nIn the detailed responses that follow, we will address each of the reviewer’s concerns\npoint by point, with reference to the specific revisions made in the manuscript.\n1. There is an inconsistency in the reported sensitivity. The Abstract and the last\nparagraph of the Introduction state 4.69 V kPa⁻¹, whereas the main text and the\nConclusion cite 4.36 V kPa⁻¹. This inconsistency reduces clarity and should be\ncorrected and justified.\nResponse: Thank you very much for pointing out this issue. The error was caused by a\nclerical mistake during our repeated testing of the sensor sensitivity. We have carefully\nreviewed the sensitivity data of the sensor in the manuscript, corrected the relevant\nwritten errors, and supplemented the voltage data under different pressures (Table 2).\nModification:\nIn Abstract part\nLine 27\n“…high force sensing sensitivity (4.36 V/kPa),…”\nIn Introduction part\nLine 116\n“…outstanding pressure sensitivity (4.36 V/kPa)…”\nIn Fabrication and characterization of TCCT sensor part\nLine 319-320\n“…Al electrode configuration (see supplementary material for calculation details and\nthe data listed in Table 2).…”\nIn Supplementary materials part\nTable 2\nTable 2 | Piezoelectric voltage (peak-to-peak) as a function of pressure.\nPressure (kPa) LM/TPU electrodes (V) Al electrodes (V)\n0.14 1.32 0.54\n0.32 1.78 0.92\n0.50 2.48 1.30\n0.94 4.87 2.29\n1.49 6.21 3.74\n2.24 8.10 4.66\n2.86 12.37 6.17\n4.48 14.70 8.10\n4.10 17.49 11.20\n5.43 23.15 15.22\n2. The claim that TMCM-CdCl preserves its molecular ferroelectricity in the TPU\n3\ncomposite is unconvincing. While the authors emphasize multiple intermolecular\ninteractions with TPU, such interactions could also disrupt the crystalline structure\nrequired for ferroelectricity. This is reflected in Figure 2g, where the original split\ndiffraction peaks merge after embedding. Moreover, the SHG signal in Figure 2i is\ninsufficient, as it can result from interfacial polarization or partial dipole alignment\nrather than intrinsic ferroelectricity. Without corroborating evidence (e.g., P-E loops or\ndomain imaging), the conclusion is unsupported.\nResponse: To confirm that TMCM-CdCl preserves its molecular ferroelectricity in\ncommercial atomic force microscope (AFM, Asylum Research MFP-3D) and\npiezoresponse force microscopy (PFM) which is based on the AFM with an AC drive\nvoltage applied to the conductive tip. Conductive Pt/Ir-coated silicon probes (EFM-50,\nNanoworld) were used for domain imaging and polarization switching studies, with a\nnominal spring constant of ~2.8 nN/nm and a free-air resonance frequency of ~75 kHz.\nPFM testing was conducted on the 5 wt% TMCM-CdCl /TPU fibers to qualitatively\n3\nexamine the ferroelectric domain structure and piezoelectric properties. Fig. R1 or\nSupplementary Fig. 6 shows the surface topography of the composite fibers, with a\nselected segment of the composite fibers highlighted. Fig. R2 or Supplementary Fig. 7\npresents the corresponding topographic and phase images of the selected fiber region.\nThe response of PFM demonstrates the presence of piezoelectricity in the fibers. After\napplying voltage to a single fiber through the conductive probe, by comparing the phase\nimages before and after voltage application (middle/right columns in Fig. R2), a\nsignificant rearrangement and polarization reversal of the domain structures within the\nfibers can be observed, providing direct evidence of ferroelectricity. The typical in-\nplane and out-of-plane PFM amplitude and phase images show distinct domain\nstructure distributions in the two modes, indicating that TMCM-CdCl on the fibers\n3\nexhibits different in-plane and out-of-plane polarization components, which\ncorresponds to its multipolar axis characteristics. Then we characterized the local\npolarization switching behavior on the fiber through switching spectroscopy PFM\n(SSPFM) measurement. The reversal of polarization was recorded off-field by PFM\nphase and amplitude signals when the V , a triangular pulse square wave, and\ndc\nsuperimposed Vac were applied to the fiber through the conductive tip. The PFM phase\ncurve shows a square-shaped hysteresis loop with a 180° contrast under the electric\nfield, and the PFM amplitude curve shows a typical butterfly shape. These curves offer\ncompelling quantitative evidence for the switching and hysteresis behaviors of\nferroelectric polarization (Fig. R3 or Supplementary Fig. 8).\nModification:\nIn Fabrication and characterization of TCCT fibers part\nLine 211-222\n“…The ferroelectric piezoelectric properties of the TCCT fibers were characterized by\nPiezoresponse Force Microscopy (PFM). The selected fiber morphology is shown in\nSupplementary Fig. 6. The typical in-plane and out-of-plane PFM amplitude and phase\nimages show distinct domain structure distributions in the two modes, confirming the\npresence of spontaneous polarization in the fibers and the differences between in-plane\nand out-of-plane components also corresponds to the multipolar axis characteristics of\nTMCM-CdCl (Supplementary Fig. 7). Meanwhile, the difference in phase imaging\n3\nbefore and after the application of voltage also confirms the presence of ferroelectricity.\nUnder the electric field, the dependence of amplitude and phase on voltage displays\ntypical butterfly and hysteresis loops, respectively, offering compelling quantitative\nevidence for polarization switching and hysteresis behaviors of ferroelectric\npolarization (Supplementary Fig. 8).…”\nIn Measurements and characterization part\nLine 701-705\n“…The ferroelectricity of the TCCT fibers was characterized using an atomic force\nmicroscope (AFM, Asylum Research MFP‑3D) with an AC drive voltage applied to the\nconductive tip. Conductive Pt/Ir-coated silicon probes (EFM-50, Nanoworld) were used\nfor domain imaging and polarization switching studies, with a nominal spring constant\nof ~2.8 nN/nm and a free-air resonance frequency of ~75 kHz.…”\nWe have added Supplementary Fig. 6 (Fig. R1), Supplementary Fig. 7 (Fig. R2), and\nSupplementary Fig. 8 (Fig. R3), along with corresponding descriptions.\nFig. R1. (Supplementary Fig. 6) Surface topography of TMCM-CdCl /TPU fibers.\n3\na, 20 μm scale. b, 2 μm scale (red box indicates the test part).\nFig. R2. (Supplementary Fig. 7) The ferroelectricity of TMCM-CdCl /TPU fibers.\n3\na, PFM topography and in-plane phase images before and after the voltage of 5 wt%\nTMCM-CdCl /TPU fibers. b, Out-of-plane PFM phase images before and after the\n3\nvoltage of the same region, respectively.\nFig. R3. (Supplementary Fig. 8) Phase and amplitude signal curves of TMCM-\nCdCl /TPU fibers under electric field. a, Amplitude−voltage butterfly loop. b,\n3. In Figure 2g, the XRD patterns of the TCCT composite clearly show the\ncharacteristic diffraction peaks of TMCM-CdCl , confirming its crystalline presence.\nvibrational features only very weakly, despite the nominally identical filler content.\nThis inconsistency raises questions about the actual structural and chemical state of TMCM-CdCl in the TPU matrix. The authors should clarify this discrepancy and\n3\nprovide further evidence (e.g., deconvoluted FTIR spectra, Raman analysis).\nResponse: As you pointed out, the Cl related vibrational features appear relatively weak\nin the original FTIR spectra, mainly due to the low content of TMCM‑CdCl and the\n3\nshielding effect of the TPU polymer matrix. To clarify this discrepancy, we utilized\nRaman spectroscopy to analyze the Cl‑related vibrational features around 810 cm-1 in\nTPU fibers, TCCT fibers, and TMCM‑CdCl crystals (Chem. Res. Chinese Universities,\n3\n2022, 38, 1394-1399). Both Fig. R4 or Supplementary Fig. 4 and its enlarged view in\nthe 760-860 cm-1 region (Fig. R5 or Fig. 2h) demonstrate the presence of C‑Cl\nvibrations in TCCT fibers, confirming the successful incorporation of TMCM‑CdCl\n3\ninto the TPU fibers. In addition, we performed deconvolution analysis on the FTIR\nspectral region of 800-700 cm-1 (Science, 2019, 363, 1206-1210). Quantitative fitting\nresults (Fig. R6 or Supplementary Fig. 5) show that the relative integrated area of the\ncharacteristic peak in this region significantly increased from 16.57% for TPU fibers to\n20.01%. This net increase in intensity is also an important indication of the introduction\nof C‑Cl structures, further confirming the successful incorporation of TMCM‑CdCl\n3\ninto the TPU fibers.\nModification:\nIn Fabrication and characterization of TCCT fibers part\nLine 198-204\n“…Furthermore, comparative analysis of the Raman spectra of TPU fibers, TCCT\nfibers, and TMCM-CdCl crystals reveals that Cl‑related vibrational features are\n3\npresent only in the pure crystal and the TCCT composite fibers, as shown in\nSupplementary Fig. 4 and its expanded view of the 760-860 cm-1 region (Fig. 2h).\nFourier transform infrared (FTIR) spectroscopy demonstrates an enhanced\ncharacteristic peak in the 700-800 cm-1 range, which further confirms the introduction\nof the C-Cl structure (Supplementary Fig. 5).…”\nWe have updated Fig. 2h (Fig. R5) and added new Supplementary Fig. 4 (Fig. R4) and\nSupplementary Fig. 5 (Fig. R6).\nFig. R4. (Supplementary Fig. 4) Raman spectra of TPU fibers, TCCT fibers, and\nTMCM-CdCl crystals.\n3\ncrystals in the 760-860 cm-1 region, with the blue area indicating the vibrational\nmodes associated with C-Cl bonds.\nFig. R6. (Supplementary Fig. 5) FTIR spectra. a, TPU fibers, TCCT fibers, and\nTMCM-CdCl crystals. b, Deconvolution analysis in the 700-800 cm⁻¹ spectral region.\n3\n4. In Figure 2k, the stress-strain curves show unexpected trends: the modulus at 1 wt%\nappears higher than at 3 wt%, and the ultimate stress at 10 wt% is similar to 5 wt%.\nThese inconsistencies are counterintuitive, and the authors should clarify the reasons\nfor this behavior.\nResponse: In response to the counterintuitive stress-strain curves noted earlier, we\nhypothesized that micro-defects at the edges of the initial samples might have skewed\nthe results. To rule out these artifacts, we repeated the tensile tests using standard\ndumbbell-shaped specimens prepared by a high-precision ultraviolet laser processing\nsystem (MHX-10-006) (Fig. R7). The updated results (Fig. R8 or Fig. 2k) reveal a clear\ntrend. With increasing TMCM-CdCl crystal content, both the strength and Young’s\n3\nmodulus of the TCCT fibers gradually improved, while the elongation at break\nprogressively decreased. This behavior can be attributed to the higher density of stress\nconcentration points introduced in the flexible matrix as filler concentration rises.\nEspecially under high loading, the crystals tend to agglomerate, forming structural\ndefects that further intensify the modulus mismatch between the rigid fillers and the\nTPU matrix, ultimately leading to a reduction in fiber ductility.\nThese revised data correct the earlier discrepancies and confirm a consistent correlation\nbetween the composite’s mechanical properties and the filler concentration.\nFig. R7. Dumbbell-shaped tensile specimen (unit: mm).\nModification:\nIn Introduction part\nLine 116\n“…strain performance (109%)…”\nIn Fabrication and characterization of TCCT fibers part\nLine 233\n“…the maximum strain from 141% at 1% content to 53% at 15% content (Fig. 2k).…”\nIn Conclusions part\nLine 488\n“(109% maximum strain)”\nWe have updated Fig. 2k (Fig. R8) and Supplementary Fig. 13b (Fig. R9), and revised\nthe description of the tensile data in the manuscript accordingly.\nFig. R8. (Fig. 2k) Ductility of TCCT fibers at different contents (1-15 wt%).\nFig. R9. (Supplementary Fig. 13b) Comparative tensile fracture curves of 1 wt%\nTCCT fibers versus integrated TCCT sensor.\n5. In Page 8, line 256-257, the authors attribute reduced output at 10 wt% to aggregation\nand uneven polarization. However, they previously emphasized that strong interactions\nwith TPU ensure uniform dispersion, which is contradictory. At such a low loading,\nsevere aggregation is unlikely, raising doubts about the stability of the ferroelectric\npolarization within the composite. The authors should clarify this inconsistency.\nResponse: Our previous explanation regarding the relationship between concentration\nvariations and output performance was indeed not precise enough. TCCT fibers were\nprepared by electrospinning a precursor solution containing TMCM-CdCl crystals and\nindeed achieve uniform dispersion during the solution stage. The local aggregation\nobserved at high concentrations mainly stems from the instability of the electrospinning\nprocess, rather than inherent compatibility issues between the materials. With\nincreasing concentration of TMCM-CdCl crystals, the conductivity of the precursor\n3\nsolution significantly improves, leading to an increase in the surface charge density of\nthe jet. This not only reduces the fiber diameter but also intensifies the instability of the\njet—a phenomenon consistent with previous literature reports (RSC appl. polym., 2024,\n2, 634). As shown in Fig. R10 or Supplementary Fig. 19, the beads formed due to jet\ninstability create spot-like dense regions on the fiber surface (10% and 15%). EDS\nmapping (Fig. R11 or Supplementary Fig. 20) further reveals the aggregation of Cl\nelements within these spot-like dense regions (yellow areas). Such uneven aggregation\nresults in a decline in output performance (Angew. Chem. Int. Ed., 2020, 59, 10368-\n10373). Therefore, the TCCT fibers exhibit optimal output performance at a 5%\nconcentration.\nModification:\nIn Fabrication and characterization of TCCT sensor part\nLine 286-296\n“…However, as the content continues to increase, the enhanced conductivity of the\nprecursor solution exacerbates the instability of the jet (35). Therefore, at\nconcentrations of 10% and 15%, the beads formed due to jet instability create spot-like\ndense regions on the fibers surface (10% and 15%) (Supplementary Fig. 19). EDS\nanalysis indicated a tendency for Cl elements to aggregate at these defect sites\n(Supplementary Fig. 20). Such microstructural inhomogeneities caused a non-uniform\ndistribution of the polarization field, thereby compromising the macroscopic\npiezoelectric output. In contrast, the 5 wt% TCCT fibers not only maintained a\nhomogeneous dispersion of Cl elements but also possessed a significantly higher\neffective content compared to the 1 wt% and 3 wt%, ultimately demonstrating the best\npiezoelectric performance.…”\nWe added new Supplementary Fig. 19 (Fig. R10) and Supplementary Fig. 20 (Fig. R11).\nFig. R10. (Supplementary Fig. 19) Morphological of TCCT fibers with different\nTMCM-CdCl crystal contents.\ndifferent TMCM-CdCl crystal contents.\n3\n6. In Figure 3g, LM/TPU is the main system, yet the authors provide full loading-\ndependent data only for Al/TPU, while LM/TPU is represented by a single 5 wt% point.\nSince Al is merely a reference, one dataset would suffice; the comprehensive trend\nshould have been shown for LM/TPU. Please clarify this data selection.\nResponse: The previous data selection focused on the optimal content of TMCM-CdCl\n3\ncrystals in the TCCT fibers with Al electrodes. This was intended to establish a baseline\nfor comparing electrode performance under identical fiber conditions, thereby\nhighlighting the superiority of the LM/TPU electrodes. Your suggestion to supplement\nthe comprehensive trend of LM/TPU electrodes is highly valuable. We have added the\noverall performance trend for the LM/TPU electrodes.\nModification:\nIn Fabrication and characterization of TCCT sensor part\nLine 296-300\n“…As shown in Fig. 3g, the TCCT fibers with LM/TPU electrodes exhibited\nsignificantly higher output voltages than those with Al electrodes across different\nTMCM-CdCl crystal doping levels. Supplementary Fig. 21 provides a comparative\n3\nanalysis of the voltage and current output curves for 5 wt% TCCT fibers under the two\nelectrode configurations.…”\nLine 340\n“…and electrode configurations…”\nWe have revised Fig. 3g (Fig. R12) by adding the voltage variation trends of TCCT\nfibers with LM/TPU electrodes under different contents.\nFig. R12. (Fig. 3g) Piezoelectric response of TCCT sensor with different TMCM-\nCdCl crystals contents (1-15 wt%) and electrode configurations under the\n3\npressure of 1 kPa.\n7. In Figure 3h, the pressure-dependent voltage responses already encompass the\ninformation that is later repeated in Figure 3i. The latter appears redundant, as it does\nnot add new insights beyond the linear plots. The authors should justify the necessity\nof Figure 3i or consider moving it to the Supporting Information.\nResponse: We have moved Fig. 3i to the Supplementary materials as suggested. The\nnewly modified Fig. 3i demonstrates the voltage output stability of the TCCT sensor\nunder a mechanical loading of 1-3 Hz.\nModification:\nIn Fabrication and characterization of TCCT sensor part\nLine 322-324\n“…Under distinct pressures (0.5, 1, and 4 kPa), the TCCT sensor generated voltage\nwaveforms with progressively increasing amplitude while maintaining signal stability\n(Supplementary Fig. 23). We evaluated the frequency stability of the TCCT sensor at\n1-3 Hz, and the experimental results showed that its output voltage could maintain\nstability (Fig. 3i).…”\nWe have updated Fig. 3i (Fig. R13) and changed the original Fig. 3i to the current\nSupplementary Fig. 23 (Fig. R14).\nFig. R13. (Fig. 3i) Piezoelectric response of TCCT sensor across 1-3 Hz frequency\nrange.\nFig. R14. (Supplementary Fig. 23) Voltage curves of TCCT sensors at pressures of\n0.5, 1, and 4 kPa.\n8. In Figure 4e, the underlying mechanism is explained in Note 2, which attributes the\nsensitivity enhancement solely to cross-sectional reduction and stress increase. This\nexplanation appears highly idealized for an electrospun fibrous mat, which is porous\nand anisotropic. The definition of an “effective cross-section” is not straightforward,\nand stress distribution is likely non-uniform due to fiber orientation and interfacial\nconstraints. Moreover, potential variations in the piezoelectric coefficient (d ) under\n31\nstrain, as well as the trade-off between sensitivity enhancement and frequency shift, are\nnot addressed. The authors should provide experimental evidence (e.g., cross-sectional\nimaging, finite-element simulations, or polarization analysis) to support the\nassumptions behind equations (S5–S8).\nResponse: We sincerely appreciate the reviewer’s insightful reflection on our proposed\nmechanism. We fully agree with the view that attributing the improvement in sensitivity\nsolely to “increased stress due to the reduction of the effective cross-sectional area” is\nan oversimplification. The changes in the piezoelectric properties of the TMCM-CdCl\n3\ncrystal during the stretching process also contribute significantly to the enhancement in\nsensitivity, and the current theoretical model cannot adequately explain this\nimprovement mechanism. Through a combination of finite-element simulations (FEA)\nand SEM characterization, we have confirmed that this phenomenon arises from a dual\nmechanism: intrinsic piezoelectric enhancement of the crystal and synergistic\noptimization of the macroscopic structure.\nOur team has previously demonstrated that strain can significantly enhance the\npiezoelectric response of TMCM-CdCl crystals (Adv. Mater. 2023, 35, 2211584).\ninvestigated. To address this, we established a mechanical simulation model (material\nparameters are listed in Table 3). The simulation results for TCCT fiber indicate that\nthe TPU matrix effectively transfers stress (Fig. R16 or Supplementary Fig. 30). Under\na macroscopic strain of 10%, noticeable stress concentration occurs around the\nembedded TMCM-CdCl crystals. More critically, owing to the relatively soft nature of\n3\nthe crystals, an axial tensile strain of approximately 0.78% is generated within them.\nThis strain value can induce the emergence of metastable phases within the crystal\nmaterial, which directly leads to an enhancement of the intrinsic piezoelectric response\nof the crystal.\nTo precisely reveal the microstructural evolution of the TCCT fiber network during\nstretching and eliminate individual variations between samples, we employed high-\nprecision laser cutting technology to extract two samples from adjacent regions of the\nsame TCCT fiber: one maintained in its original state (untreated), and the other\npre-stretched with 60% tensile strain for comparative characterization (Fig. R17 or\nSupplementary Fig. 31). Using the intersection method, we compared changes in pore\ncompactness of the fibers before and after stretching (Fig. R17b and d), and found that\nat the 5-micrometer scale, the stretched fiber network exhibited a significantly\nincreased number of intersections with lines 1-5 (Fig. R17e). This quantitatively\nconfirms the mechanical stretching-induced film densification effect. High-density\nfiber distribution is crucial for enhancing the performance of piezoelectric fiber devices\n(Nat. Commun., 2013, 4, 1633; Small, 2026, 22, e09387). The compact arrangement\nimproves mechanical coupling and stress transfer efficiency between fibers, ensuring\nthat external loads are more effectively transmitted to the TMCM-CdCl crystals\n3\nembedded in the TPU matrix. Therefore, the enhanced sensitivity of the TCCT sensor\ndoes not stem from a single factor but rather from the synergistic effects of strain-\ninduced enhancement of the intrinsic piezoelectric response of the crystals and\nimproved stress transfer efficiency resulting from the optimized fiber network structure.\nAnalysis of sensitivity enhancement and frequency shift: Indeed, the increase in\nstructural stiffness caused by pre-stretching leads to a shift in the resonant frequency of\nthe device toward higher frequencies (Supplementary note 2). As shown in Fig. R20 or\nSupplementary Fig. 33 (The details of the improvements to this spectrum analysis plot\nin our response to question 9), FFT analysis demonstrate that the maximum amplitude\nof the stretched TCCT sensor shifts toward higher frequencies. This physical-level\nmodulation of frequency response does not negatively affect speech recognition\ncapability; instead, it plays a positive role. Specifically, the unstretched TCCT sensor,\ndue to its limited sensitivity, suffers from baseline noise that drowns out weak high-\nfrequency components present in the original digital signal, resulting in missing\ninformation in the spectrum. In contrast, the 20% TCCT sensor significantly enhanced\npiezoelectric response, successfully captures and reconstructs some of the high-\nfrequency characteristic peaks. Thus, while the change in stiffness introduces slight\nshifts in resonance peaks, the enhancement in sensitivity plays a decisive role in\nimproving the spectral consistency with the source signal. This effectively addresses\nthe issue of high-frequency information loss in the unstretched state, making its\nspectrogram closer to that of the original digital signal.\nModification:\nIn Introduction part\nLine 118-121\n“…This improvement primarily originates from the synergistic effect between the\nstrain-induced intrinsic piezoelectric enhancement of the crystals and the increased\nstress transfer efficiency resulting from the densified fiber network.…”\nIn Responses to acoustic forces part\nLine 374-386\n“…Fig. 4e elucidates the mechanism of strain-enhanced piezoelectric response. Under\nthe same acoustic excitation, lateral stretching induces a certain strain in the TMCM-\nCdCl crystals within the fibers (Supplementary Fig. 30, with material parameters\n3\nprovided in Table 3), which directly enhances the intrinsic piezoelectric response of the\ncrystals (45). Simultaneously, it promotes a denser internal structure of the TCCT fibers\n(Supplementary Fig. 31). The compact structure improves the mechanical coupling and\nstress transfer efficiency between the fibers (46), ensuring that external loads are more\neffectively transmitted to the crystals embedded in the TPU matrix. The synergistic\neffect of strain-induced enhancement of the intrinsic piezoelectric response of the\ncrystals and improved stress transfer efficiency resulting from the optimized fiber\nnetwork structure enhances the electromechanical conversion efficiency of the TCCT\nsensor, resulting in a significant increase in surface charge density and output\nvoltage.…”\nIn Applications and demonstrations part\nLine 433-435\n“…Although the change in stiffness caused by stretching introduces slight resonance\npeak shifts, the enhancement in sensitivity plays a decisive role in improving the\nspectral consistency with the original signal.…”\nIn Conclusions part\nLine 498-503\n“…Notably, while mechanical strain enhances the intrinsic piezoelectric response of\nthe TMCM-CdCl crystals embedded in the polymer matrix, it also induces significant\n3\ndensification of the fiber network. This compact network structure greatly optimizes\nmechanical coupling efficiency, enabling the minute vibrations generated by acoustic\nwaves to be more effectively captured by the internal crystals, thereby achieving an\noverall enhancement in piezoelectric output.…”\nIn Supplementary materials part\nTable 3\nTable 3 | Material properties used in finite element analysis.\nYoung's Modulus Poisson’s Ratio\nMaterial Density (ρ) Ref.\n(E) (v)\nTMCM-CdCl 17.5 GPa 0.3 2.15 g/cm3 (9)\nTPU 0.25 GPa 0.4 1.23 g/cm3\nand (10)\nBased on the results from FEA and SEM experiments, we have updated the mechanism\nschematic illustrating strain-enhanced piezoelectric response in the manuscript (Fig. 4e\nor Fig. R15) and removed the original note 2. Additionally, Fig. R16 or\nSupplementary Fig. 30 and Fig. R17 or Supplementary Fig. 31 have been added for\nfurther support.\nFig. R15. (Fig. 4e) Mechanism schematic for strain-enhanced piezoelectric\nresponse.\nFig. R16. (Supplementary Fig. 30) Internal mechanical evolution of the TCCT\nfiber under tensile strain. a, Stress distribution cloud diagram. b, Strain evolution\ntrend (crystal strain approximately 0.78%).\nFig. R17. (Supplementary Fig. 31) Microstructural evolution of the TCCT fiber\nnetwork before and after stretching. a, b, SEM images of the fiber network in the\nunstretched state (loose and porous structure). c, d, Fiber morphology after applying\n60% pre-stretch strain (densification). e, Compare the number of intersection points\non five lines (lines 1-5) of the fiber network before and after stretching.\n9. In Figures 5b and 5c, the original sound signal and the sensor outputs are visibly\ndifferent. Supplementary Fig. 19 further shows that the original signal has a clear\nfeature at 600-700 Hz, while the TCCT sensor, with or without strain, exhibits only\nweak response in this range. This indicates significant distortion and undermines the\nclaim of faithful sound reproduction. The authors should address this limitation directly.\nResponse: Thank you for your insightful observations regarding signal fidelity and\nfrequency response characteristics. The discrepancy between the original speech signal\nand the sensor output signal does indeed exist. This is primarily attributed to mechanical\ndamping caused by environmental background noise as well as the sensor’s own\nthickness and mounting method. Similar signal attenuation phenomena have also been\nfrequently reported in comparable studies (Nature, 2022, 603, 616-623; Sci. Adv., 2025,\n11, eadv2801). To demonstrate the performance advantages of the TCCT sensor, we\ncompared the original signal, the signal from a commercial sensor (LDT0-028K), and\nthe signal from the TCCT sensor. As the most widely used flexible piezoelectric sensor,\nthe LDT0-028K features mature technology and is frequently employed in vibration\ndetection and acoustic monitoring (IEEE Trans. Instrum. Meas., 2022, 71, 8502312;\nAdv. Funct. Mater., 2025, 35, 2415501). Using it as a control group clearly highlights\nthe advantages of the device developed in this work in terms of sensitivity and response\ncharacteristics. The results show that although the commercial piezoelectric sensor\nexhibits a slightly higher output voltage, its fidelity to the original sound is lower (Fig.\nR18b or Fig. 5b). The STFT spectrogram clearly demonstrates the superiority of the\nTCCT sensor in sound recognition tasks, as its response characteristics in the 1000-\nR18c or Fig. 5c).\nTo enhance the response capability of the TCCT sensor in the 600–700 Hz frequency\nband, we optimized the device structure by reducing the volume of the electrode\nprecursor solution from 1.5 mL to 1.0 mL, effectively decreasing the thickness of the\nelectrode layer. The optimized sensor demonstrates excellent restoration capability for\nthe original speech signal. Experimental results indicate that the TCCT sensor under a\nstretched state exhibits a higher output voltage compared to its unstretched state (Fig.\nR19a or Supplementary Fig. 32a). The STFT spectrogram (Fig. R19b or Supplementary\nFig. 32b) further confirms that the stretched sensor can more faithfully capture the\ncharacteristics of the original sound signal. In addition, FFT analysis (Fig. R20 or\nSupplementary Fig. 33) reveals that, compared with commercial sensors, the TCCT\nsensor captures richer frequency components across the broad frequency range of 0-\nband is significantly enhanced, effectively addressing the previously observed\ninadequate response in this frequency range.\nModification:\nIn Applications and demonstrations part\nLine 414-431\n“…Comparative analysis of the piezoelectric signals acquired by the commercial sensor\n(LDT0-028K) and the TCCT sensor during continuous audio playback demonstrates\nthat the TCCT sensor achieves excellent fidelity in reconstructing the original\nwaveform (Fig. 5b and Supplementary video 2). Further time-frequency analysis via\nshort-time Fourier transform (STFT) reveals that the TCCT sensor completely\npreserves the complex time-varying frequency characteristics of the original speech\nwithin the 0-2000 Hz range, whereas the commercial sensor exhibits severe information\nloss (Fig. 5c). Furthermore, a comparison of the piezoelectric signals collected by the\nTCCT sensor before and after stretching reveals a significant increase in output voltage,\nalong with an improvement in its high-frequency response capability (Supplementary\nFig. 32). Fast Fourier transform (FFT) analysis reveals that the TCCT sensor\noutperforms commercial sensor in capturing and reconstructing key frequency\ncomponents across the 0-1000 Hz spectrum (Supplementary Fig. 33). Under 20% strain,\nthe sensor enabled partial reconstruction of frequency components within the 1000-\npeaks owing to the intrinsic damping of the device. Concurrently, a shift of the peak\nresponse toward higher frequencies was observed.…”\nIn Device fabrication of TCCT sensor part\nLine 682\n“…a certain amount of (1-1.5 ml)…”\nWe have updated Fig. 5b-c (Fig. R18) and Supplementary Fig. 32 (Fig. R19), and added\nSupplementary Fig. 33 (Fig. R20).\nFig. R18. (Fig. 5b and c) Sound recognition under strain-enhanced conditions. b,\nWaveforms of three audio signals: original audio, and waveforms converted the\ncommercial sensor and the TCCT sensor. c, Corresponding voice spectrograms of the\nsignals.\nFig. R19. (Supplementary Fig. 32) Piezoelectric response of the TCCT sensor\nunder 15 s music. a, Waveform comparison at strain 0% and 20%. b, Corresponding\nvoice spectrograms of the signals.\nFig. R20. (Supplementary Fig. 33) Comparison of FFT response characteristics\nbetween the original audio, commercial sensor and the piezoelectric response of\nthe TCCT sensor (strain 0% and 20%) under 15 s music.\nReviewer: 2 The scope of the paper entitled \"Strain-Enhanced Stretchable Molecular\nFerroelectric Acoustic Fiber\" presents an acoustic sensor fabricated through\nelectrospinning technology by integrating molecular ferroelectric crystal TMCM-\nCdCl with thermoplastic polyurethane (TPU), demonstrating high stretchability (>100%\n3\nstrain) and piezoelectric response (4.69 V/kPa). However, the novelty of the material\nsystem (TMCM-CdCl /TPU) and the electrospinning fabrication process should be\n3\nmore clearly stated. The proposed strain-enhancement mechanism needs sufficient\nexperimental evidence and rigorous validation. The following comments should be\naddressed by major revision before this paper is suitable for publication in Nature\nCommunications.\nResponse: We fully agree with the reviewer’s perspective and sincerely appreciate the\nopportunity to revise our manuscript. We have made the following important additions\nand modifications to the article, aiming to further demonstrate the rigor of this study\nand highlight the distinct differences between our work and existing research:\n1. First, we systematically analyzed the differences between our work and previous\nstudies, thereby more clearly emphasizing the innovation and scientific contribution of\nthis research.\n2. Second, we conducted detailed characterization of the microscopic morphological\nevolution of the fibers under strain. Drawing on our previous research foundation, we\nclarified the two main influencing factors of the strain enhancement mechanism.\n3. Finally, we added a series of supplementary data and figures to provide a more\ncomprehensive research approach.\nThe specific modifications to the manuscript will be presented point by point in the\nfollowing responses.\n1. The authors emphasize that the molecular ferroelectric material TMCM-CdCl\n3\nexhibits a high piezoelectric coefficient and rich tunability, positioning it as a key\nsolution to the application bottlenecks of traditional piezoelectric materials in flexible\nacoustic sensing. However, composite systems of TMCM-CdCl with polymer matrices,\n3\nincluding TPU, have been previously reported (Nat. Commun. 2024, 15, 8636), and the\ndevice performance has no significant improvements. Furthermore, electrospun fibers\nintegrating TMCM-CdCl with polymers have been utilized in acoustic sensors (Adv.\narticulate the novelty and distinctiveness of their work relative to these prior studies.\nResponse: We thank the reviewer for their insightful understanding and constructive\nsuggestions regarding this field. We have carefully studied Ref. 1 (Nat. Commun., 2024,\n15, 8636) and Ref. 2 (Adv. Mater., 2025, 37, 24092). Although our work is also based\non TMCM-CdCl crystals, it differs fundamentally from the aforementioned references\n3\nin terms of research approach, structural design, and core enhancement mechanisms.\nCurrently, the cutting-edge trend in next-generation acoustic sensors is shifting from\nrigid devices toward flexible, stretchable electronics compatible with the human\ninterface. For such applications, the stability of devices under deformation—\nparticularly tensile strain-is crucial. However, existing piezoelectric acoustic sensors\nface an inherent dilemma: inorganic ceramics (e.g., PZT) possess high piezoelectric\ncoefficients, yet their high modulus limits low-frequency sensitivity and flexibility;\nmeanwhile, piezoelectric polymers (e.g., PVDF) offer lower modulus but significantly\nweaker piezoelectric response. Balancing a high piezoelectric response with excellent\nelastic mechanical properties remains a highly challenging problem in the field (Science,\n2023, 381, 540-544). Furthermore, during dynamic stretching, interfacial mechanical\nmismatch between the electrode and the piezoelectric active layer often leads to contact\nfailure, severely limiting the stability of the sensor (Nat. Commun., 2023, 14, 4000).\nAccordingly, we designed the TCCT sensor, a fully stretchable piezoelectric acoustic\ndevice, by integrating high-performance TMCM-CdCl crystals with elastic TPU. In\n3\ncontrast to Refs. 1 and 2, our work introduces a unique interfacial interlocking\nengineering approach, which not only addresses the challenges of achieving\nstretchability and maintaining interfacial stability in piezoelectric sensors under strain,\nbut also realizes a strain‑induced sensitivity enhancement effect. Therefore, our work\ndemonstrates significant novelty and uniqueness in overcoming the key bottlenecks of\nflexible acoustic sensors, as elaborated below:\n1) Utilizing TPU elastomer and an intimately interlocked interface design, we prepared\na stretchable piezoelectric nanofiber acoustic sensor exhibiting excellent interfacial\nstability.\nBased on TMCM-CdCl crystals and elastic TPU, we fabricated a stretchable TCCT\n3\nsensor via electrospinning. Benefiting from the abundant hydrogen bonds and\nintermolecular interactions between TMCM-CdCl and TPU molecular chains, the\n3\ncrystals and the elastic matrix achieve tight molecular‑level integration, significantly\nenhancing the mechanical stability of the nanofibers under tensile deformation.\nBuilding on this, we further introduced a unique interlocked hierarchical interface\ndesign. This synergistic combination of “molecular‑bonding enhancement” and\n“interface interlocking structure” not only physically ensures the interfacial integrity of\nthe device during dynamic large‑strain stretching (Fig. 3e and Supplementary video 1),\nbut also improves the electrical output performance of the TCCT sensor (Fig. 3g and\nh). In comparison, although Ref. 1 also utilizes interfacial interactions between\nmaterials, its porous scaffold design primarily serves to amplify stress for enhanced\ncompressive output, making it ill‑suited for tensile applications. Ref. 2 employs a PVP\nmatrix whose intrinsic brittleness prevents the device from being stretchable. Regarding\nthe electrode design, both Ref. 1 and Ref. 2 adopt conventional planar contact\nelectrodes (such as copper foil or silver coating) without accounting for the mechanical\nmismatch between metal electrodes and soft polymer matrices.\n2) The TCCT sensor exhibits strain-induced acoustic sensing sensitivity enhancement.\nThe TCCT sensor exhibits a unique strain-enhanced piezoelectric response, which\ndistinguishes it significantly from those reported in Refs 1 and 2. This behavior results\nfrom the synergistic effect of two mechanisms: strain-induced densification of the fiber\nnetwork enhancing stress transfer efficiency, and strain-induced volution of the\nmolecular ferroelectric domain structure enhances piezoelectric response (Adv. Mater.\n2023, 35, 2211584). This characteristic is crucial for dynamic acoustic sensing, as it\nprevents stretching from degrading performance and instead actively improves the\nsignal-to-noise ratio (SNR) of the TCCT sensor under tensile strain. Experiments show\nthat the device maintains high accuracy in speech recognition even under different\nlevels of stretching strain. This demonstrates the distinct practical advantages of the\ndevice in complex real‑world wearing scenarios-such as those involving skin\ndeformation during movement.\nModification:\nIn Abstract part\nLine 28-30\n“…Crucially, we demonstrate a strain-induced sensitivity enhancement effect, where\nthe acoustic sensitivity of the sensor increases from 15.03 mV/dB to 30.16 mV/dB\nunder strain.…”\nIn Introduction part\nLine 96-105\n“…For example, the use of a porous TPU framework loaded with TMCM-CdCl\n3\ncrystals has enabled piezoelectric composite materials with high power output (29).\nAdditionally, TMCM-CdCl /PVP composite fibers prepared via the electrospinning\n3\nprocess have been successfully applied in low-frequency sound recognition (30). These\nstudies have confirmed the application potential of the TMCM-CdCl and polymer\n3\ncomposite system. However, the electromechanical coupling behavior of molecular\nferroelectric crystals and polymer matrices under dynamic tensile deformation remains\nunexplored, and its underlying mechanisms are still unclear. Furthermore, the interface\ncontact issues between the composite material and electrodes during dynamic\ndeformation have not yet been considered.…”\nLine 108-110\n“…Utilizing the robust intermolecular interactions between the crystals and the matrix\neffectively improved the mechanical tensile stability of the fibers.…”\n2. The authors' claim that \"This improvement primarily originates from the strain-\ninduced stress concentration effect\" is currently supported only by the macroscopic\nelectrical output of the device and a theoretical formulation. To strengthen this\nconclusion, additional experimental evidence is recommended.\nResponse: According to your suggestions, we have refined the description of the\nmechanism by which strain enhances sensitivity. Our team has previously demonstrated\nthat strain can significantly enhance the piezoelectric response of TMCM-CdCl\n3\ncrystals (Adv. Mater. 2023, 35, 2211584). However, the underlying mechanisms within\nthe polymer composite system have not yet been investigated. For TMCM-CdCl\n3\ncrystals encapsulated in the polymer, it is challenging to verify the strain behavior of\nthe crystals under stretching through microscopic characterization. To address this issue,\nwe established a mechanical simulation model (material parameters are listed in Table\n3). The simulation results for TCCT fiber indicate that the TPU matrix can effectively\ntransfer stress (Fig. R22 or Supplementary Fig. 30). Under a macroscopic strain of 10%,\ndue to the inherent softness of the crystal itself, an axial tensile strain of approximately\n0.78% is generated within the crystal. This strain value can induce the formation of a\nmetastable phase within the crystal material, thereby directly enhancing the intrinsic\npiezoelectric response of the crystal.\nSimultaneously, to precisely reveal the microstructural evolution of the TCCT fiber\nnetwork during stretching and eliminate individual variations between samples, we\nemployed high-precision laser cutting technology to extract two samples from adjacent\nregions of the same TCCT fiber: one maintained in its original state (untreated), and the\nother pre-stretched with 60% tensile strain for comparative characterization (Fig. R23\nor Supplementary Fig. 31). Using the intersection method, we compared changes in\npore compactness of the fibers before and after stretching (Fig. R23b and d), and found\nthat at the 5-micrometer scale, the stretched fiber network exhibited a significantly\nincreased number of intersections with lines 1-5 (Fig. R23e). This quantitatively\nconfirms the mechanical stretching-induced film densification effect. High-density\nfiber distribution is crucial for improving the performance of piezoelectric fiber devices\n(Nat. Commun., 2013, 4, 1633; Small, 2026, 22, e09387). This compact arrangement\nenhances mechanical coupling and stress transfer efficiency between fibers, ensuring\nthat external loads can be more effectively transmitted to the TMCM-CdCl crystals\n3\nembedded in the TPU matrix.\nTherefore, we conclude that the improvement in the sensitivity of the TCCT sensor\ndoes not stem from a single factor but rather results from the synergistic effect of strain-\ninduced enhancement of the intrinsic piezoelectric response of the crystals and the\nimproved stress transfer efficiency brought about by the optimized fiber network\nstructure.\nModification:\nIn Introduction part\nLine 118-121\n“…This improvement primarily originates from the synergistic effect between the\nstrain-induced intrinsic piezoelectric enhancement of the crystals and the increased\nstress transfer efficiency resulting from the densified fiber network.…”\nIn Responses to acoustic forces part\nLine 374-386\n“…Fig. 4e elucidates the mechanism of strain-enhanced piezoelectric response. Under\nthe same acoustic excitation, lateral stretching induces a certain strain in the TMCM-\nCdCl crystals within the fibers (Supplementary Fig. 30, with material parameters\n3\nprovided in Table 3), which directly enhances the intrinsic piezoelectric response of the\ncrystals (45). Simultaneously, it promotes a denser internal structure of the TCCT fibers\n(Supplementary Fig. 31). The compact structure improves the mechanical coupling and\nstress transfer efficiency between the fibers (46), ensuring that external loads are more\neffectively transmitted to the crystals embedded in the TPU matrix. The synergistic\neffect of strain-induced enhancement of the intrinsic piezoelectric response of the\ncrystals and improved stress transfer efficiency resulting from the optimized fiber\nnetwork structure enhances the electromechanical conversion efficiency of the TCCT\nsensor, resulting in a significant increase in surface charge density and output\nvoltage.…”\nIn Conclusions part\nLine 500-505\n“…Notably, while mechanical strain enhances the intrinsic piezoelectric response of\nthe TMCM-CdCl crystals embedded in the polymer matrix, it also induces significant\n3\ndensification of the fiber network. This compact network structure greatly optimizes\nmechanical coupling efficiency, enabling the minute vibrations generated by acoustic\nwaves to be more effectively captured by the internal crystals, thereby achieving an\noverall enhancement in piezoelectric output.…”\nIn Supplementary materials part\nTable 3\nTable 3 | Material properties used in finite element analysis.\nYoung's Modulus Poisson’s Ratio\nMaterial Density (ρ) Ref.\n(E) (v)\nTMCM-CdCl 17.5 GPa 0.3 2.15 g/cm3 (9)\nTPU 0.25 GPa 0.4 1.23 g/cm3\nand (10)\nBased on the results from FEA and SEM experiments, we have updated the mechanism\nschematic illustrating strain-enhanced piezoelectric response in the manuscript (Fig.\nR21 or Fig. 4e) and removed the original note 2. Additionally, Fig. R22 or\nSupplementary Fig. 30 and Fig. R23 or Supplementary Fig. 31 have been added for\nfurther support.\nFig. R21. (Fig. 4e) Mechanism schematic for strain-enhanced piezoelectric\nresponse.\nFig. R22. (Supplementary Fig. 30) Internal mechanical evolution of the TCCT\nfiber under tensile strain. a, Stress distribution cloud diagram. b, Strain evolution\ntrend (crystal strain approximately 0.78%).\nFig. R23. (Supplementary Fig. 31) Microstructural evolution of the TCCT fiber\nnetwork before and after stretching. a, b, SEM images of the fiber network in the\nunstretched state (loose and porous structure). c, d, Fiber morphology after applying\n60% pre-stretch strain (densification). e, Compare the number of intersection points\non five lines (lines 1-5) of the fiber network before and after stretching.\n3. The presented cyclic tensile stability tests yield excellent results. However, for\npractical deployment, the sensor must withstand environmental challenges such as\nvarying temperature and humidity. Specifically, the stability of the water-soluble\nTMCM-CdCl component requires thorough investigation, particularly regarding\n3\npotential dissolution and recrystallization under cyclic humidity conditions and overall\nperformance retention in high-humidity environments.\nResponse: To investigate the environmental stability of the TCCT fibers in practical\nconditions, we subjected it to high-humidity cycling and high-temperature testing\nwithin a custom-built cyclic temperature and humidity test system (Fig. R24a).\nRegarding humidity stability, the piezoelectric response of the unencapsulated TCCT\nfibers was recorded at 1 Hz throughout humidification and dehumidification cycles. As\nshown in Fig. R24b, the sensor’s performance is significantly influenced by ambient\nhumidity due to the water-soluble nature of the TMCM-CdCl crystals. The\n3\npiezoelectric output exhibits a clear decreasing trend as the relative humidity (RH) rises.\nNotably, in a high-humidity environment of 80% RH, the piezoelectric response of the\nunencapsulated TCCT fibers nearly diminishes completely. However, this degradation\nis reversible. Upon returning to a low-humidity environment, the piezoelectric output\nrecovers due to the recrystallization of TMCM-CdCl on the surface of fibers. And this\n3\nphenomenon can be attributed to the hygroscopic and water-soluble nature of the\nTMCM-CdCl crystals. In terms of thermal stability (Fig. R24c), the TCCT fibers\n3\ndemonstrates excellent stability across a broad temperature range from 300 K to 360 K,\nwith its voltage response remaining steady. However, as the temperature further\nincreases and approaches the Curie temperature (T ) of TMCM-CdCl (Science, 2017,\nc 3\n357, 306-309), the piezoelectric response begins to attenuate markedly until it vanishes,\nwhich is consistent with the ferroelectric phase transition characteristics of this material.\nFig. R24. Effect of temperature and humidity on TCCT fibers. a, Schematic of the\nexperimental testing system. b, Variation in piezoelectric response under relative\nhumidity (20–80% RH). c, Variation in piezoelectric response under temperature (300–\nSubsequently, to verify the effectiveness of the encapsulation strategy, we subjected the\nPI-encapsulated device to the same humidity variation test (Fig. R25). In sharp contrast\nto the unencapsulated device, the encapsulated one exhibited excellent environmental\nstability. Even as the ambient humidity increased from 20% RH to 80% RH, its\npiezoelectric output voltage remained stable throughout, with no significant\nperformance degradation observed.\nFig. R25. Piezoelectric response of TCCT fibers under different encapsulation\nconditions at 20–80% RH.\n4. The authors compare the sensor performance of Al electrodes with LM/TPU\nelectrodes, attributing the inferior performance of the Al electrodes to the formation of\nan air gap at the interface with the TCCT electrospun film. The rationale for selecting\nAl as the benchmark for comparison should be explicitly stated. Additionally, to more\ndirectly address the air-gap issue, a control experiment involving the deposition of Al\nor other metal electrodes directly onto the TCCT film should be conducted, and how\nabout its performance.\nResponse: The piezoelectric sensor features a typical sandwich-like structure,\nconsisting of top and bottom electrodes with a piezoelectric active layer in between.\nAmong these, aluminum (Al) foil is commonly used as a conventional electrode due to\nits ease of use (Nat. Commun., 2024, 15, 819; Adv. Mater., 2025, 37, 2507859; Nat.\nCommun., 2022, 13, 4867). To investigate the influence of interfacial contact conditions,\nwe compared the piezoelectric output of aluminum (Al) foil electrodes, sputtered gold\n(Au) electrodes, and LM/TPU polymer electrodes under a pressure of 0.5 kPa (Fig.\nR26). Compared with Al electrodes, the Au electrodes prepared by sputtering achieve\ntighter conformal contact with the TCCT fibers, increasing the effective contact area\nand thereby enhancing charge collection efficiency. However, charge exchange\nbetween the Au electrode and the active layer occurs essentially via a two-dimensional\nplanar interface, implying that charge collection is largely confined to the outermost\nsurface of the material. In contrast to the surface coverage of Au electrodes, the\nLM/TPU electrode permeates the fiber network to establish a unique three-dimensional\nmechanically interlocked interface. This structural design not only minimizes\ninterfacial impedance but also transitions the mechanism to effective volumetric charge\nharvesting, leading to a significant improvement in the voltage response of the device\nunder mechanical stimulation (Nat. Commun., 2023, 14, 4000, ACS Appl. Mater.\nInterfaces, 2019, 11, 7379−7386). Therefore, the TCCT sensor equipped with the\nLM/TPU electrodes demonstrates significantly superior voltage output performance\ncompared to the other two electrodes configurations.\nFig. R26. Piezoelectric output under different electrode conditions. a, Al foil\nelectrodes. b, Sputtered Au electrodes. c, LM/TPU electrodes.\n5. The authors repeatedly emphasize the critical role of the interlocked intermediate\nlayer. However, the formation mechanism of this layer and its specific interaction with\nthe piezoelectric layer remain unclear. Experimental evidence and characterization\ndetailing the layer's formation process and interface properties are required to support\nthese claims.\nResponse: Fig. R27 illustrates the dynamic formation and evolution process of the\ninterlocked intermediate layer between the TCCT fibers and the LM/TPU electrode.\nThis unique interfacial structure originates from the in situ dissolution-recrystallization\neffect induced by the residual solvent (N, N-dimethylformamide, DMF) in the LM/TPU\nelectrode solution on the TCCT nanofibers. The specific evolution mechanism is\nanalyzed as follows:\n5 min: The experiment began by placing the substrate coated with the LM/TPU\nprecursor solution in an environment at 40°C and 50% relative humidity for a 0.25 h\npretreatment to partially volatilize the solvent, followed immediately by the\ncommencement of electrospinning. During the initial spinning stage (5 min), due to the\nhigh concentration of residual DMF solvent on the electrode surface, the deposited\nTCCT fibers were rapidly dissolved upon contact with the interface. At this point, SEM\nimages showed almost no intact fibrous structures on the surface, leaving only\nrecrystallized TMCM-CdCl crystal particles. EDS mapping indicated that, as the\n3\noverlayer was extremely thin and partially dissolved, the Ga signal from the interior of\nthe electrode was clearly visible, while the Cl signal representing the crystals was weak\nand dispersed.\n0.25 h: As the electrospinning process proceeded and the DMF solvent continued to\nevaporate, the dissolving capacity at the electrode surface gradually weakened. At\napproximately 0.25 h, a visible fibrous network began to appear on the surface,\nalthough the fibers boundaries remained blurred and exhibited significant fusion,\nmarking the initial formation of the interlocked interface. At this stage, EDS revealed\nan inhomogeneous distribution of Cl elements due to the random deposition of fibers,\nwhile the Ga signal began to weaken as the surface fibers coverage increased.\n0.5 h-1 h: As the solvent further evaporated, SEM observations revealed that the area\nof fibers regions with blurred contours (partially dissolved) gradually decreased (as\nindicated by the red circles in the image), while the area of fibers with intact\nmorphology progressively expanded. This phenomenon is attributed to the local\ninhomogeneity of solvent evaporation on the LM/TPU electrode surface: in micro-\nregions with more residual solvent, fibers still underwent dissolution and fusion,\nleading to local enrichment of Cl elements (crystal aggregation); whereas in regions\nwith less solvent, fibers began to retain their intact morphology.\n2 h: When electrospinning was continued for 2 h, the physical image showed that the\nsample surface was completely covered by a dense white TCCT fibers. SEM images\nconfirmed the formation of a clear and uniformly networked nanofibers structure on the\nsurface, indicating that the solvent in the underlying electrode had completely\nevaporated and no longer exerted a dissolving effect on newly deposited fibers. At this\nstage, EDS mapping revealed a homogeneous distribution of Cl elements across the\nentire area, while the Ga signal was almost completely absent due to the shielding effect\nof the thick fibrous layer. This signifies that a dense interlocked intermediate layer,\nalong with a complete upper piezoelectric active layer, has been successfully\nconstructed.\nTo construct the complete sensor, the counter electrode on the opposite side underwent\nthe same pretreatment process: it was dried under identical conditions for 0.25 hours to\nachieve a semi-dry state where the surface DMF had not yet fully evaporated.\nSubsequently, it was attached to the surface of the previously prepared TCCT fibers\nlayer, and the entire assembly was dried for 12 h. By leveraging the residual solvent in\nthe counter electrode for re-dissolution and penetration, an interlocked structure was\nsimilarly constructed at the top interface, thereby completing the fabrication of the high-\nperformance TCCT sensor.\nIn terms of interfacial characteristics, the experimental results demonstrate that\nconstructing an interlocked intermediate layer between the electrode and the\npiezoelectric active layer significantly enhances the device’s stability under stretching\nwhile maintaining reliable interfacial contact (Fig. R28 or Fig. 3e and Supplementary\nvideo 1). Compared with traditional planar contact, this interlocking structure greatly\nexpands the effective contact area, thereby significantly improving the piezoelectric\noutput of the TCCT sensor ((Fig. R29 or Fig. 2h). We attribute the performance\nenhancement to the optimized distribution of the local electric field and the expansion\nof the effective polarization volume facilitated by the interlocked interface, which in\nturn strengthens the capacitive coupling efficiency. This mechanism has been\npreviously investigated and reported by Li et al (Nat. Commun., 2023, 14, 4000).\nFig. R27. Interfacial evolution at different time points.\nFig. R28. (Fig. 3e) Optical micrograph under tensile strain (0-40%).\nFig. R29. (Fig. 3h) Piezoelectric response of TCCT sensor with different electrodes\nacross 0-6 kPa pressure range.\n6. The molecular ferroelectric material TMCM-CdCl , which possesses a high\n3\npiezoelectric coefficient (d = 220 pC/N), was incorporated into a TPU matrix to\n33\nfabricate composite fibers. It is crucial to investigate whether this fabrication process\ncompromises its piezoelectric coefficient.\nResponse: We highly thank you for this valuable suggestion. We collected charge data\nunder various applied forces using a Keithley 6514, and calculated d by linear fitting\n33\nof the charge versus force data (Nat. Commun., 2024, 15, 819, Nat. Commun., 2022, 13,\n5076). The size of the fibers is 15 mm  15 mm. The collected charge versus force data\nis shown in Fig. R30 or Supplementary Fig. 18. 5% TCCT composite fibers exhibits\nthe maximum d of approximately 32.00 pC/N.\n3 33\nsuppose possible reasons for this include: (1) Polarization misalignment. Since TMCM-\nCdCl is distributed in polycrystalline form within the composite material, the\n3\npolarization cannot be fully aligned in the out-of-plane direction. As a result, despite its\nmultiple polarization axes, it still cannot exhibit a piezoelectric coefficient comparable\nto that of a single crystal. (2) The high elastic modulus and Poisson’s ratio of TPU\ninducing internal stress, and thereby reducing the stress amplification factor in TMCM-\nCdCl . (3) Low polarization charge mobility. In the later work, we will continue to\n3\noptimize the composite design and fabrication to enhance the performance of the\ncomposite materials.\nModification:\nIn Fabrication and characterization of TCCT sensor part\nLine 279-282\n“…The d of the TCCT fibers was also measured by linear fitting of charge the charge\n33\nversus force data. As calculated, 5% TCCT fibers exhibits the maximum d of\n33\napproximately 32.00 pC/N (Supplementary Fig. 18, A to E).…”\nWe have added Supplementary Fig. 18 (Fig. R30).\nFig. R30. (Supplementary Fig. 18) Charge versus force data for calculation d . a,\n33\n1%. b, 3%. c, 5%. d, 10%. e, 15%.\n7. The authors state in both the Introduction and Conclusion that the TCCT fiber\nexhibits excellent tensile properties, citing a maximum strain of 102%. However, the\ncorresponding tensile data and analysis appear to be absent from the Results and\nDiscussion section.\nResponse: In the Results and Discussion section, we have supplemented the\ncorresponding tensile data and related analysis. The changes in some of the data are due\nto retesting conducted in response to suggestions from other reviewers. The new test\nresults not only further confirm our previous conclusions but also reveal a clearer trend.\nModification:\nIn Fabrication and characterization of TCCT sensor part\nLine 282-285\n“…To achieve a balance between satisfactory electrical output and mechanical strain\ncapability, we determined the optimal content of TMCM-CdCl to be 5%. At this level,\n3\nthe TCCT fiber exhibits a maximum strain of approximately 109%.…”\nIn Conclusions part\nLine 491-496\n“…While robust interfacial bonding ensures the fracture resistance of the composite\nfibers under strain, the maximum strain of the fibers significantly decreases from 141%\nat 1% content to 53% at 15% content as the crystal content increases. This phenomenon\nis attributed to the high loading of TMCM-CdCl crystals, which act as stress\n3\nconcentration points within the TPU fibers and simultaneously restrict the motion of\npolymer chain segments.…”\nWe have updated Fig. 2k (Fig. R31) and added descriptions of the updated data in both\nthe Introduction and Conclusion sections.\nFig. R31. (Fig. 2k) Ductility of TCCT fibers at different contents (1-15 wt%).\n8. The authors claim in Figure 4g that the TCCT sensor achieves a wider frequency\ndetection range compared to the current state-of-the-art piezoelectric acoustic sensors.\nHowever, the literature survey appears incomplete. Several recent reports on\npiezoelectric acoustic sensors with broad frequency detection ranges appear to have\nbeen overlooked (e.g., Nano Energy 2025, 143, 111312; Adv. Funct. Mater. 2024, 34,\n2312699; Nature 2022, 603, 616; Nano Energy 2022, 101, 107610).\nResponse: We have thoroughly reviewed the relevant literature as suggested and further\nexplored the latest research progress in this field. On this basis, we have supplemented\nperformance comparisons in the frequency detection range further with two similar\nworks (Nano Energy 2025, 143, 111312; Nano Energy 2022, 101, 107610). Although\nthe comparison results indicate that some flexible piezoelectric acoustic sensors indeed\noutperform the current TCCT sensor in terms of frequency response range, it must be\nemphasized that, in the field of stretchable (rather than merely flexible) acoustic sensing,\nthis work still demonstrates advantages in terms of overall device performance. More\nimportantly, our device possesses a strain-enhanced acoustic sensing capability, which\nis absent in the aforementioned comparative works and endows it with unique\napplication value in dynamic deformation environments.\nModification:\nIn Responses to acoustic forces part\nLine 391-392\n“…Benchmarked against state-of-the-art flexible piezoelectric acoustic sensors (Fig.\n4g) (2, 15, 16, 47-51),…”\nLine 394-398\n“…Although comparison results indicate that some flexible piezoelectric acoustic\nsensors do outperform the current TCCT sensor in terms of frequency response range,\nthe TCCT sensor possesses a strain-enhanced acoustic sensing capability, which\nvalidates its significant advantages for voice detection applications.”\nWe have updated Fig. 4g (Fig. R32).\nFig. R32. (Fig. 4g) Compare the acoustic frequency range of the proposed TCCT sensor\nwith that of existing acoustic sensors.\n9. The authors investigate the effect of strain on the sensor's acoustoelectric conversion\ncapability, concluding that 20% strain yields the maximum voltage output. This\nconclusion, however, is based on data from only three strain states (0%, 10%, and 20%).\nWhether a higher strain could yield a greater response\nResponse: Following your valuable suggestion, we further characterized the device's\nacoustoelectric conversion performance across a broader strain range (0%–40%). The\ntest results (Fig. R33 or Supplementary Fig. 27) show that under an 80 dB, 100 Hz\nacoustic field, the sensor's output voltage indeed exhibited a continuous upward trend\nas strain increased up to 40%. However, once the strain exceeded 20%, the rate of\nvoltage increase slowed noticeably. To balance high sensitivity output with long‑term\nmechanical reliability, we selected the 0%-20% strain range as the optimal working\ncondition in subsequent experiments. These supplementary data and related discussions\nhave been fully incorporated into the revised manuscript.\nModification:\nIn Responses to acoustic forces part\nLine 362-367\n“…Subsequently, we investigated the influence of strain on the sensor’s acousto-\nelectric conversion capability under an 80 dB, 100 Hz acoustic field (Supplementary\nFig. 27). The results show that the output voltage of the TCCT sensor continued to\nincrease with strain (0-40% strain), but the rate of voltage rise slowed significantly once\nstrain exceeded 20%. Therefore, to clearly demonstrate the improvement resulting from\nstretching, subsequent experiments focused on the 0-20% strain range....”\nLine 368-370\n“…the TCCT sensor under 20% strain exhibits significantly superior acoustoelectric\nconversion capability and acoustic pressure sensitivity compared to its performance at\n0% and 10% strain (Fig. 4c, d)....”\nWe have added Supplementary Fig. 27 (Fig. R33).\nFig. R33. (Supplementary Fig. 27) Piezoelectric output of the TCCT sensor under\ndifferent strain conditions.\n10. The macroscopic deformation of the piezoelectric fiber during stretching will\ninevitably generate a significant strain-induced electrical signal. Will there be any\ninteraction or interference between this strain-induced signal and the target\nacoustic signal?\nResponse: Indeed, when piezoelectric fibers undergo macroscopic deformation (such\nas stretching or releasing), strain-induced charges are inevitably generated. To assess\nthe impact of such signals on the target acoustic signal, we compare in detail the time-\ndomain waveforms and frequency-domain characteristics of the TCCT sensor during\ndynamic stretching in Fig. R34. As shown in Fig. R34a, the stretching action does\nintroduce baseline fluctuations (highlighted by the red box). For this audio segment, the\nsensor in the stretched state is able to capture richer acoustic details compared to the\nunstretched state, thereby making the signal closer to the original digital audio. To\nverify signal fidelity, we performed a normalized FFT spectrum analysis (Sci. Adv. 2021,\n7, eabe5683) (Fig. R34b). The results confirm that although the intensity of the time-\ndomain signal increases due to stretching, its frequency components (e.g., ~57 Hz, ~234\nHz, ~415 Hz) remain remarkably consistent with those of the original signal. This\nindicates that the strain-induced signal generated by stretching primarily manifests as a\nlinear amplification of the acoustic signal, without introducing significant frequency\ndistortion. This further demonstrates the reliable speech recognition capability of the\ndevice under dynamic deformation.\nFig. R34. Effect of stretching on the TCCT sensor. a, Original acoustic signal and\nthe output response of the sensor in its pristine and stretched states. b, FFT analysis of\nthe output signals under each condition: the original signal, the TCCT sensor, and the\nstretched TCCT sensor.\n11. The claim that \"under 20% strain, the TCCT sensor exhibits amplified response\ncharacteristics at higher frequencies\" requires substantiation. This claim is not\nconvincingly supported by the data presented in Figure 4c, which shows negligible\ndifferences in the high-frequency voltage output across the different strain states. To\nrobustly support this conclusion, additional data characterizing the frequency response\nunder various strain states is essential (e.g., modal analysis).\nResponse: The phrase “higher frequencies” used in our original manuscript was indeed\nimprecise. In accordance with your suggestions, we have supplemented additional data\non the frequency response under different strain conditions. The results show that at 20%\nstrain, an increase in output is observed across the entire frequency range of 30-5000\nHz, with a more pronounced enhancement in the 30-1000 Hz range, while the difference\nin voltage output within the 1000-5000 Hz range is relatively small. To clarify this, we\nenlarged the voltage variation in the 1000-5000 Hz region in Fig. 4c (Fig. R35),\nconfirming that the voltage output under 20% strain is indeed significantly higher than\nthat in the unstretched state. The nearly identical visual appearance in the original plot\nis due to the scaling of the figure.\nFig. R35. Voltage variation trends of the TCCT sensor at frequencies of 1000-5000\nHz under strains of 0%, 10%, and 20%.\nModification:\nIn Applications and demonstrations part\nLine 436-438\n“…Specifically, under 20% strain, the acoustic response characteristics of the TCCT\nsensor are enhanced. Compared to the unstretched state, the stretched sensor can more\neffectively capture the high-frequency details of the original sound signal.…”\nWe have updated Fig. 4b (Fig. R36) and Fig.4c (Fig. R37). Furthermore, to further\nsupport this conclusion, we have provided real-time raw waveform data at different\nfrequencies in Supplementary Fig. 28 (Fig. R38).\nFig. R36. (Fig. 4b) Response of unstretched TCCT sensor to acoustic waves (input:\nsteady sinusoidal signal).\nFig. R37. (Fig. 4c) Frequency-dependent response under strain 0-20% (sound pressure\n0.2 Pa).\nFig. R38. (Supplementary Fig. 28) Piezoelectric response of the TCCT sensor at 0%,\n10%, and 20% strain under varying frequencies. a, 30 Hz-100 Hz. b, 200 Hz-1000\nHz. c, 1500 Hz-5000 Hz.\n12. Visual inspection of Figures 5b and 5c suggests that the piezoelectric signal captured\nbefore straining aligns more closely with the original audio waveform and exhibits finer\nacoustic details compared to the signal after straining. This observation appears to\ncontradict the central claim that strain enhances sensing performance.\nResponse: Thank you for your careful observation. Indeed, visually, the piezoelectric\nsignal waveform captured in the unstretched state appears closer to the original audio\nin terms of its envelope. This is mainly due to the differences in the response\ncharacteristics of the device to sound signals of different frequencies under varying\nstretching states. The improvement in sensing performance defined in this study is\nprimarily reflected in the enhancement of sensitivity. Compared to the unstretched\ndevice, the stretched TCCT sensor exhibits a higher response voltage amplitude and\nstronger SNR for the same acoustic signal. Based on this, we conclude that the\nperformance in the stretched state is significantly better than in the unstretched state.\nHowever, to address the signal fidelity issue you pointed out and ensure that high\nsensitivity does not come at the expense of fine acoustic details, we further optimized\nthe sensor structure. Specifically, we believe that the thicker electrode layer introduces\nadditional mechanical damping, suppressing some sound details. Therefore, we reduced\nthe thickness of the electrode layer by decreasing the volume of the electrode precursor\nsolution from 1.5 mL to 1.0 mL. Subsequently, the output of the optimized TCCT sensor\nwas compared with the original signal and that of a commercial piezoelectric sensor.\nAs the most widely used flexible piezoelectric sensor, the LDT0-028K features mature\ntechnology and is frequently employed in vibration detection and acoustic monitoring\n(IEEE Trans. Instrum. Meas., 2022, 71, 8502312; Adv. Funct. Mater., 2025, 35,\n2415501). Using it as a control group clearly highlights the advantages of the device\ndeveloped in this work in terms of sensitivity and response characteristics. The\nexperimental results demonstrate that compared to commercial piezoelectric sensors\n(LDT0-028K), the optimized TCCT sensor exhibits excellent fidelity to the original\nspeech signal (Fig. R39 or Fig. 5b). The STFT spectrogram clearly illustrates the\nadvantage of the TCCT sensor in sound recognition tasks, particularly in the 1000-2000\nHz frequency range, where its frequency response characteristics are significantly\nsuperior to those of commercial sensors (Fig. R39 or Fig. 5c). Fig. R40 or\nSupplementary Fig. 32a shows that the output voltage of the TCCT sensor in the\nstretched state is higher than that in the unstretched state. Furthermore, both STFT (Fig.\nR40 or Supplementary Fig. 32b) and FFT (Fig. R41 or Supplementary Fig. 33) confirm\nthat applying stretching strain enhances the ability of the TCCT sensor to capture\nfeatures from the original speech signal.\nModification:\nLine 414-431\nIn Applications and demonstrations part\n“…Comparative analysis of the piezoelectric signals acquired by the commercial sensor\n(LDT0-028K) and the TCCT sensor during continuous audio playback demonstrates\nthat the TCCT sensor achieves excellent fidelity in reconstructing the original\nwaveform (Fig. 5b and Supplementary video 2). Further time-frequency analysis via\nshort-time Fourier transform (STFT) reveals that the TCCT sensor completely\npreserves the complex time-varying frequency characteristics of the original speech\nwithin the 0-2000 Hz range, whereas the commercial sensor exhibits severe information\nloss (Fig. 5c). Furthermore, a comparison of the piezoelectric signals collected by the\nTCCT sensor before and after stretching reveals a significant increase in output voltage,\nalong with an improvement in its high-frequency response capability (Supplementary\nFig. 32). Fast Fourier transform (FFT) analysis reveals that the TCCT sensor\noutperforms commercial sensor in capturing and reconstructing key frequency\ncomponents across the 0-1000 Hz spectrum (Supplementary Fig. 33). Under 20% strain,\nthe sensor enabled partial reconstruction of frequency components within the 1000-\npeaks owing to the intrinsic damping of the device. Concurrently, a shift of the peak\nresponse toward higher frequencies was observed.…”\nWe have updated Fig. 5b-c (Fig. R39) and Supplementary Fig. 32 (Fig. R40), and added\nSupplementary Fig. 33 (Fig. R41).\nFig. R39. (Fig. 5b and c) Sound recognition under strain-enhanced conditions. b,\nWaveforms of three audio signals: original audio, and waveforms converted the\ncommercial sensor and the TCCT sensor. c, Corresponding voice spectrograms of the\nsignals.\nFig. R40. (Supplementary Fig. 32) Piezoelectric response of the TCCT sensor under\n15 s music. a, Waveform comparison at strain 0% and 20%. b, Corresponding voice\nspectrograms of the signals.\nFig. R41. (Supplementary Fig. 33) Comparison of FFT response characteristics\nbetween the original audio, commercial sensor and the piezoelectric response of\nthe TCCT sensor (strain 0% and 20%) under 15 s music.\n13. Figure 5f and 5g present the data before straining and a mixture of pre- and post-\nstraining data, respectively. However, the dataset corresponding solely to the post-\nstraining state is missing, which is crucial for a direct evaluation of the strain's\neffect. Furthermore, the observed decline in accuracy for the mixed dataset requires a clear\nexplanation.\nResponse: We thank you for your valuable suggestions. We have incorporated the post-\nstrain dataset into Supplementary Fig. 35 or Fig. R42.\nHere’s a more detailed explanation of the observed decline in accuracy for the mixed\ndataset:\nThe decline in accuracy for the mixed dataset primarily stems from changes in data\ndistribution rather than from sensor failure itself. In the code, we directly merged the\nspeech signals collected under before stretching and after stretching conditions into the\nmixed dataset and trained the same CNN-LSTM model on it. Since the waveform\namplitude, and spectral features of the same speech category after stretching exhibit\ncertain shifts compared to those before stretching, the intra-class variations of the same\ncategory in the feature space significantly increase, making the inter-class decision\nboundaries more difficult to learn. However, the model’s ability to maintain a high\nrecognition rate under these more complex, mixed conditions demonstrates that the\nTCCT sensor can still provide distinguishable speech features after stretching.\nModification:\nIn Applications and demonstrations part\nLine 462-463\n“…Distinct clustering is observed for signals acquired in the unstretched state and after\nstretching (Fig. 5f, Supplementary Fig. 35a).”\nWe have updated Supplementary Fig. 35 (Fig. R42)\nFig. R42. (Supplementary Fig. 35) The sound recognition performance of the TCCT\nsensor. a, Eigenvector matrices processed by t-SNE after 50 iterations for after\nstretching data. b, Confusion matrix for the before stretching. c, Confusion matrix for\nthe after stretching (20% strain).\nReviewer: 3 The manuscript presents stretchable molecular ferroelectric acoustic fibers\nwith strain-enhanced sound perception capabilities. The fibers exhibit exceptional\nspeech recognition capabilities, with enhanced sensitivity as strain increases. This study\ncould be interesting for the audience working on molecular ferroelectrics. I recommend\nthe publication of the manuscript in Nature Communications, while there are some\nissues have to be addressed first.\nResponse: The positive feedback and valuable suggestions from the reviewers\nregarding this work are sincerely appreciated. To further highlight the innovativeness\nof this study, the reviewers’ advice has been carefully adopted, and the following\nsignificant additions and revisions have been implemented:\n1. Firstly, descriptions of the background and underlying principles have been expanded\nto enhance readability for a multidisciplinary audience.\n2. Secondly, a systematic analysis of related cutting-edge works has been conducted.\nThe novelty and scientific contributions of this study are clarified through a detailed\ncomparison in terms of material selection and device fabrication.\n3. Thirdly, imprecise phrasing throughout the manuscript have been thoroughly\ncorrected to ensure academic rigor.\n4. Finally, a series of supplementary data and illustrations has been incorporated to\nestablish a more comprehensive research framework.\nSpecific details of these revisions are presented point-by-point in the following sections.\n1. The authors used a class of hybrid organic-inorganic molecular perovskite\nferroelectrics. Considering the broad readership of Nature Communications, the authors\nare suggested to add a description in the appropriate place within the main text about\nthe advantages of molecular ferroelectrics when compared to traditional piezoelectric\nmaterials like PZT, BTO, and PVDF.\nResponse: Thank you for your valuable suggestions. In consideration of the diverse\nand interdisciplinary readership of Nature Communications, we fully agree on the\nnecessity of elucidating the distinctions among different types of piezoelectric materials.\nAccordingly, we have added a detailed description in the Introduction section regarding\nthe differences between conventional piezoelectric materials (such as PZT, BTO, and\nPVDF) and novel molecular ferroelectrics, thereby helping readers better understand\nthe background and significance of this research.\nModification:\nIn Introduction part\nLine 68-73\n“Conventional piezoelectric materials often face a trade-off between electrical\nperformance and mechanical properties. Inorganic piezoelectric ceramics, represented\nby PZT and BTO, exhibit relatively high piezoelectric coefficients (d ) but suffer from\n33\nexcessive rigidity and complicated fabrication processes (19). On the other hand,\norganic piezoelectric polymers such as PVDF offer excellent flexibility, yet their d\n33\nremain relatively low (20).…”\n2. The manuscript introduces a molecular ferroelectric composite material prepared by\nincorporating TMCM-CdCl into a thermoplastic polyurethane (TPU) matrix. During\n3\nthe spinning process, the electrode layer is assembled to achieve the fabrication of a\nstretchable ferroelectric acoustic device. What are the differences and advantages of the\nmolecular ferroelectric composite materials and device fabrication method proposed in\nthe manuscript compared to previously reported piezoelectric acoustic devices?\nResponse: While previous studies on TMCM-CdCl molecular ferroelectric crystals\n3\nhave been reported (Nat. Commun., 2024, 15, 8636; Adv. Mater., 2025, 37, 24092), the\npresent work exhibits essential differences from the aforementioned research in terms\nof methodology, structural design, and core enhancement mechanisms. The specific\ndistinctions are outlined as follows:\n1) Utilizing TPU elastomer and an intimately interlocked interface design, we prepared\na stretchable piezoelectric nanofiber acoustic sensor exhibiting excellent interfacial\nstability.\nBalancing a high piezoelectric response with excellent elastic mechanical properties\nremains a highly challenging problem in the field (Science, 2023, 381, 540-544).\nFurthermore, during dynamic stretching, interfacial mechanical mismatch between the\nelectrode and the piezoelectric active layer often leads to contact failure, severely\nlimiting the stability of the sensor (Nat. Commun., 2023, 14, 4000). Based on TMCM-\nCdCl crystals and elastic TPU, we fabricated a stretchable TCCT sensor via\n3\nelectrospinning. Benefiting from the abundant hydrogen bonds and intermolecular\ninteractions between TMCM-CdCl and TPU molecular chains, the crystals and the\n3\nelastic matrix achieve tight molecular‑level integration, significantly enhancing the\nmechanical stability of the nanofibers under tensile deformation. Building on this, we\nfurther introduced a unique interlocked hierarchical interface design. This synergistic\ncombination of “molecular‑bonding enhancement” and “interface interlocking\nstructure” not only physically ensures the interfacial integrity of the device during\ndynamic large‑strain stretching (Fig. 3e and Supplementary video 1), but also improves\nthe electrical output performance of the TCCT sensor (Fig. 3g and h). In comparison,\nalthough Ref. 1 (Nat. Commun., 2024, 15, 8636) also utilizes interfacial interactions\nbetween materials, its porous scaffold design primarily serves to amplify stress for\nenhanced compressive output, making it ill‑suited for tensile applications. Ref. 2 (Adv.\nMater., 2025, 37, 24092) employs a PVP matrix whose intrinsic brittleness prevents the\ndevice from being stretchable. Regarding the electrode design, both Ref. 1 and Ref. 2\nadopt conventional planar contact electrodes (such as copper foil or silver coating)\nwithout accounting for the mechanical mismatch between metal electrodes and soft\npolymer matrices.\n2) The TCCT sensor exhibits strain-induced acoustic sensing sensitivity enhancement.\nThe TCCT sensor exhibits a unique strain-enhanced piezoelectric response, which\ndistinguishes it significantly from those reported in Refs 1 and 2. This behavior results\nfrom the synergistic effect of two mechanisms: strain-induced densification of the fiber\nnetwork enhancing stress transfer efficiency, and strain-induced volution of the\nmolecular ferroelectric domain structure enhances piezoelectric response (Adv. Mater.\n2023, 35, 2211584). This characteristic is crucial for dynamic acoustic sensing, as it\nprevents stretching from degrading performance and instead actively improves the\nsignal-to-noise ratio (SNR) of the TCCT sensor under tensile strain. Experiments show\nthat the device maintains high accuracy in speech recognition even under different\nlevels of stretching strain. This demonstrates the distinct practical advantages of the\ndevice in complex real‑world scenarios-such as those involving skin deformation\nduring movement.\nModification:\nIn Abstract part\nLine 28-30\n“…Crucially, we demonstrate a strain-induced sensitivity enhancement effect, where\nthe acoustic sensitivity of the sensor increases from 15.03 mV/dB to 30.16 mV/dB\nunder strain.…”\nIn Introduction part\nLine 96-105\n“…For example, the use of a porous TPU framework loaded with TMCM-CdCl\n3\ncrystals has enabled piezoelectric composite materials with high power output (29).\nAdditionally, TMCM-CdCl /PVP composite fibers prepared via the electrospinning\n3\nprocess have been successfully applied in low-frequency sound recognition (30). These\nstudies have confirmed the application potential of the TMCM-CdCl and polymer\n3\ncomposite system. However, the electromechanical coupling behavior of molecular\nferroelectric crystals and polymer matrices under dynamic tensile deformation remains\nunexplored, and its underlying mechanisms are still unclear. Furthermore, the interface\ncontact issues between the composite material and electrodes during dynamic\ndeformation have not yet been considered.…”\nLine 108-110\n“…Utilizing the robust intermolecular interactions between the crystals and the matrix\neffectively improved the mechanical tensile stability of the fibers.…”\n3. The d of TMCM-CdCl is 220 pC/N. What is the d of TPU/TMCM-CdCl (TCCT)\n33 3 33 3\ncomposite fibers at different contents of TMCM-CdCl ? Are the piezoelectric\n3\ncoefficients measured by electrical resonance method which is recommended by IEEE\nStandard on Piezoelectricity.\nResponse: We collected charge data under various applied forces using a Keithley 6514,\nand calculated d by linear fitting of the charge versus force data (Nat. Commun., 2024,\n33\n15, 819, Nat. Commun., 2022, 13, 5076). The size of the fibers is 15 mm  15 mm.\nThe collected charge versus force data is shown in Fig. R33 or Supplementary Fig. 18.\n5% TCCT composite fibers exhibits the maximum d of approximately 32.00 pC/N.\n3 33\nsuppose possible reasons for this include: (1) Polarization misalignment. Since TMCM-\nCdCl is distributed in polycrystalline form within the composite material, the\n3\npolarization cannot be fully aligned in the out-of-plane direction. As a result, despite its\nmultiple polarization axes, it still cannot exhibit a piezoelectric coefficient comparable\nto that of a single crystal. (2) The high elastic modulus and Poisson’s ratio of TPU\ninducing internal stress, and thereby reducing the stress amplification factor in TMCM-\nCdCl . (3) Low polarization charge mobility. In the later work, we will continue to\n3\noptimize the composite design and fabrication to enhance the performance of the\ncomposite materials.\nModification:\nIn Fabrication and characterization of TCCT sensor part\nLine 279-282\n“…The d of the TCCT fibers was also measured by linear fitting of charge the charge\n33\nversus force data. As calculated, 5% TCCT fibers exhibits the maximum d of\n33\napproximately 32.00 pC/N (Supplementary Fig. 18, A to E).…”\nWe have added Supplementary Fig. 18 (Fig. R43).\nFig. R43. (Supplementary Fig. 18) Charge versus force data for calculation d . a,\n33\n1%. b, 3%. c, 5%. d, 10%. e, 15%.\n4. Response time is an important parameter in molecular ferroelectric acoustic fibers.\nHow is the response time of the piezoelectric output of the molecular ferroelectric fibers?\nResponse: Acoustic signals are essentially high-frequency mechanical stress waves.\nThus, we characterized the electromechanical transient response of the TCCT sensor\nusing a linear motor from pressure testing. Specifically, the dynamic response of the\nsensor was tested under periodic loading at 1 Hz frequency and 0.5 kPa pressure, as\nshown in Fig. R44 or Supplementary Fig. 24. The results indicate that the signal rise\ntime (response time) of the sensor is approximately 0.03 s, enabling rapid detection of\ndynamic forces. It should be noted that this value primarily corresponds to the\nmechanical loading rate of the linear motor.\nModification:\nIn Fabrication and characterization of TCCT sensor part\nLine 324-326\n“…The TCCT sensor exhibits a response time of 0.03 s, which corresponds to the\nduration required for the voltage to rise from 10% to 90% (Supplementary Fig. 24).…”\nFig. R44. (Supplementary Fig. 24) The response time of the TCCT sensor under a\nmechanical load of 1 Hz and 0.5 kPa. a, Response voltage curve. b, Response time.\n5. Under constant pressure, what is the response trend of the ferroelectric acoustic fibers\nacross different frequencies?\nResponse: We highly thank you for your suggestions. We have evaluated the frequency\nstability of the TCCT sensor in the 1-3 Hz range, which exhibits stable and consistent\npiezoelectric output (Fig. 3i). The previous Fig. 3i has been moved to the supplementary\nmaterials.\nModification:\nIn Fabrication and characterization of TCCT sensor part\nLine 322-324\n“…We evaluated the frequency stability of the TCCT sensor at 1-3 Hz, and the\nexperimental results showed that its output voltage could maintain stability (Fig. 3i).…”\nWe have updated Fig. 3i (Fig. R45)\nFig. R45. (Fig. 3i) Piezoelectric response of TCCT sensor across 1-3 Hz frequency\nrange.\n6. Please explain why this neural network model was chosen to be used over others.\nConsidering the broad multi-disciplinary readers, the author should give the brief\nnecessary background.\nResponse: Speech signals are inherently time series data characterized by rich spectral\nfeatures and strict temporal logic. Convolutional Neural Networks (CNNs) excel at\nextracting local invariant features from high-dimensional raw data, effectively filtering\nout noise and capturing key acoustic patterns, but they lack the capability for long-\nsequence memory. In contrast, Long short-term memory (LSTM) networks are\ndesigned to process sequential data and can capture long-term temporal dependencies,\nyet they are less efficient in directly handling high-dimensional raw signals. Therefore,\nwe adopted a hybrid CNN-LSTM architecture: the CNN serves as a front-end “feature\nextractor” to reduce dimensionality and extract robust acoustic features, followed by\nthe LSTM as a back-end for temporal modeling. This synergistic design significantly\nenhances the robustness of the model in recognizing speech under different strain\nconditions.\nModification:\nIn Applications and demonstrations part\nLine 451-454\n“…. effectively filters out noise, and captures key acoustic patterns. The LSTM is\ndesigned for processing sequential data and can model the temporal dependencies in\nspeech. The combination of CNN and LSTM enhances the robustness of the model in\nrecognizing speech under different strain conditions.…”\n7. Some spelling and format mistakes should be corrected. For example, Line 181 on\nPage 6, and Line 564 on Page 19. The authors have to carefully check the English\nthroughout the manuscript.\nResponse: We have carefully reviewed the manuscript based on your reminder and\ncorrected some spelling and format mistakes.\nModification:\nIn Introduction part\nLine 81\n“…the d values of…”\nLine 193\n“…. The TCCT fibers…”\nIn Electrospinning TCCT fibers part\nLine 666\n“…. for 1 h.”\nFor your convenience of reading,\nAnswers to the reviewers in blue\nModifications of the manuscript in red\nReview round: 2\nReviewer: 1 The authors have fully addressed all comments. The revised manuscript is\nready to publish in the Nature Communications journal.\nResponse: We would like to thank you for taking the time to review our manuscript.\nYour expertise and constructive comments have significantly helped us enhance the\nquality of this work.\nReviewer: 2 The authors have adequately and convincingly addressed all reviewer\ncomments with clear revisions and supporting evidence. No further changes are\nrequired. I recommend acceptance without revision.\nResponse: We sincerely thank the reviewers for their positive feedback on our revised\nmanuscript.\nReviewer: 3 The authors have properly responded my comments and questions on the\nmanuscript. I don't have any other comments on the present manuscript. However,\nEnglish throughout the manuscript has to be further improved.\nResponse: Thank you for your valuable time and insightful comments, which have\nhelped us improve our paper. We have carefully proofread and revised the entire\nmanuscript, with a focus on correcting details such as tenses and hyphens, and refining\ncertain expressions to further enhance the language quality.\nModification:\nIn Abstract part\nLine 18-20\n“…Molecular ferroelectrics—hybrid organic-inorganic architectures that exhibit\npiezoelectric coefficients comparable to classic oxide ceramics while offering rich\ncompositional and structural tunability—…”\nLine 24\n“…we report stretchable molecular ferroelectric acoustic fibers fabricated by…”\nLine 30\n“…Crucially, a strain-induced sensitivity enhancement effect is proposed and\nverified,…”\nLine 32\n“…Furthermore,…”\nLine 34\n“…This work establishes a route…”\nIn Introduction part\nLine 55\n“…For instance,…”\nLine 66-67\n“…In contrast, piezoelectric acoustic sensors rely on thin-film vibrations induced by\nacoustic waves for sound detection. This simple yet efficient working mechanism\nprovides a feasible route toward stretchable acoustic devices (18).…”\nLine 69\n“…Conventional piezoelectric materials often suffer from…”\nLine 71-72\n“…high piezoelectric coefficients (d ) but are limited by…”\n“…owing to their attractive merits,…”\nLine 109\n“…, which serves as the piezoelectric active layer.…”\nLine 119\n“…, twice that in the unstretched state.…”\nIn Results part\nLine 129-130\n“…To address the brittleness and inflexibility of molecular ferroelectrics and thereby\nrender the resulting devices compatible with a broad range of complex working\nscenarios,…”\nLine 141\n“The electrodes employed stretchable LM/TPU composite polymer as the material.…”\nLine 146\n“…Detailed fabrication procedures…”\nIn Results part\nApplications and demonstrations\nLine 424\n“…and stretched state (Fig. 5f, Supplementary Fig. 35a).…”\nLine 428-429\n“…Although the prediction accuracy for the mixed data decreased compared to that in\nunstretched and stretched states alone (Fig. 5i and Supplementary Fig. 35b-c),…”"}]

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