Structured liquid-based reconfigurable all-liquid optical fibers

Domain: physics
Published: 2025-12-31
Editorial outcome: minor_revision

Abstract
Quartz optical fibers are brittle, difficult to repair, and lack reconfigurability, limiting their adaptability in underwater communication. To overcome these impediments, here we show reconfigurable all-liquid optical fibers (RAOFs) produced by structured liquid, tuned by the interfacial assembly and jamming of nanoparticle surfactants at the water-oil interface (interfacial tension < 10 mNm-1, refractive index contrast of 0.083). These RAOFs combine the structural stability of the interfacial assemblies with the inherent flexibility of liquids. They support real-time communication on an Ethernet platform (up to 1 Gbps), providing a practical alternative to conventional optical fibers for optical interconnects. Their liquid nature enables broken fibers to be repaired rapidly by a coalescence process. Their softness affords on-demand reconfigurability that enables in-situ fabrication of reconfigurable optical fibers and dynamic manipulation of signal transmission. RAOFs provide a versatile, self-healing, and resilient solution for optical communication systems in dynamic environments.

Introduction
Optical fibers are the primary technology for long-distance telecommunications1. They are based on the total internal reflection of light that occurs at the interface of a dielectric core with a higher refractive index (RI) layer, which is surrounded by a cladding layer with a lower RI, thus confining light propagation within the core. Commercial optical fibers are typically made from quartz to optimize performance2,3. However, traditional quartz optical fibers face limitations, including brittleness, susceptibility to fracture, difficulty in repair, and a lack of the reconfigurability required for on-demand manipulation, all stemming from the inherent mechanical properties of quartz4–6. These limitations restrict their adaptability in underwater communication (UWC). Consequently, there is a need for innovative fiber systems that preserve the essential optical functions of traditional fibers while offering additional flexibility, self-healing capabilities, and on-demand reconfigurability to meet the demands of challenging operating conditions.

In response to these challenges, researchers have explored the development of soft optical fibers by incorporating polymers and liquids, such as core-shell liquid-filled polymer fibers and hydrogel fibers7–9. While these soft fibers offer moderate flexibility in shape deformation, they require complex fabrication processes, are not easily repairable, and lack sufficient structural flexibility, e.g., optional shape deformation and topology change. Furthermore, many of these fibers are primarily used as sensors rather than for telecommunication, mainly because their structures are designed to maximize sensitivity to environmental parameters (e.g., RI, temperature, or chemical composition), which is beneficial for sensing but not required for long-distance signal transmission. The inherent similarity between these liquid-core–polymer-shell fibers and conventional all-glass fibers means that they still inherit the intrinsic limitations of solid fibers, such as fixed geometry, difficulty in repairing breakage, and relatively high optical loss, which further restrict their use in large-scale telecommunication10. In contrast, all-liquid optical fibers, formed by a continuous liquid jet of one fluid in air, show promise for greater resistance to breakage and for optical communication11. However, existing all-liquid optical fiber prototypes face significant obstacles, including difficulty in maintaining a stable liquid core without complex control systems, challenges in isolating light from the liquid stream, and air cladding, which is vulnerable to perturbations, rendering them impractical for real-world use. Therefore, there is a need to develop reconfigurable all-liquid optical fibers (RAOFs) that combine structural stability, fluidity, and telecommunication capability.

Recent studies have shown that structured liquids, formed by the self-assembly and jamming of nanoparticle surfactants (NPSs), can achieve structural stability and shape integrity. This approach provides a pathway for creating stable all-liquid fibers (ALFs) with both reconfigurability and mechanical strength12–19. The liquid interface offers an ideal platform for achieving total internal reflection due to the intrinsic refractive index difference (RID) between two different liquid media (Supplementary Fig. 1)8. While our long-term aim is to develop liquid fibers for underwater optical communication, we employ an oil-based external phase in the present study because such immiscible systems are experimentally well-established and allow precise control of interfacial and optical parameters. The RI and viscosity of the glucose–water inner phase can be conveniently tuned, providing a reliable platform to investigate interfacial self-assembly and waveguiding mechanisms.

In this work, building on the ALFs, we develop a soft, self-healing RAOF using all-liquid 3D printing with an RID of 0.083 at the interface, which enables total internal reflection and light propagation (Fig. 1a). This fiber is a promising alternative to traditional commercial optical fibers and is capable of efficient real-time communication. The fabrication of the RAOF relies on two key factors. First, the intrinsic RID at the water-oil interface supports total internal reflection of incident light, a critical prerequisite for the fiber’s functionality as an optical fiber. Second, interfacial self-assembly between oppositely charged ligands at the water-oil interface facilitates the 3D printing of ALFs, which can be produced at scale and shaped arbitrarily as required (Fig. 1b and 1c).

Results
The formation of a stable liquid tubule with structural integrity and sustained total internal reflection at the core–cladding interface is a fundamental requirement for RAOFs. Total internal reflection at a liquid-liquid interface is made possible by the RID between two immiscible liquids. To meet the criteria of chemical stability, appropriate RID, and good processability, a glucose solution and silicone oil were used. To further increase RID, the glucose concentration was increased to yield a refractive index of 1.4876, while the silicone oil had an RI of 1.4046 (Supplementary Fig. 2a). As shown in Fig. 1d, Supplementary Fig. 1, and Supplementary Video 1, the total reflection of a red light beam with a measured critical angle of \theta_measure = 71.3° was found at the oil-water interface, closely matching the theoretical value of \theta_c = 70.8°20. To evaluate whether the addition of ligands and the viscosity of the cladding oil influence the optical properties of RAOF, we systematically measured the RI of both phases under typical conditions. As shown in Supplementary Fig. 2b, the RI of the aqueous phase containing PSS and the oil phase containing N-PDMS remain nearly unchanged across the ligand concentration range used in this work (<5 wt.%). The maximum RI variation induced by ligands is less than 0.005, which is negligible compared to the RI modulation achieved by glucose (up to 0.15). In addition, control experiments were conducted with oils of different viscosities, and the results indicate that viscosity has almost no effect on the RI of the cladding phase or on the effective RI contrast of the RAOF. These results confirm that the RID in RAOF is predominantly governed by glucose concentration, while surfactants and oil viscosity contribute only marginally to the optical guiding properties.

To optimize light transmission, an appropriate light source should be used. Based on the UV-Vis spectra of the water core and oil cladding (Supplementary Fig. 2c), the broad transparency window of the system enables RAOFs to support a wide range of wavelengths. Here, red light (\lambda = 650 nm) was used due to its low absorption and attenuation in water. To test light transmission, a wavy-shaped RAOF was printed in a custom mold (Supplementary Fig. 3). Shielding plates were inserted at each bend to minimize the interference from leaked light. Upon coupling red light into the RAOF, light propagation along the inner interface was observed, with obvious leakage at the bends and coupling point (Fig. 1e), likely due to interfacial scattering at curved regions and the interface mismatch. The high RID at the oil-water interface supports total internal reflection over a larger range of incidence angles, facilitating light propagation within the RAOFs. A clear output signal confirmed the ability of the RAOF to transmit light effectively (Supplementary Fig. 4), and the observed light path closely followed the print geometry (Fig. 1f), validating light confinement within the core. To shed light on the practical application of RAOF in the real world, we coupled RAOF in a practical light communication system, and the results demonstrate that RAOF is a promising alternative to traditional commercial optical fibers in a UWC system.

Fundamentals for the preparation of reconfigurable all-liquid optical fibers
For the fabrication of the liquid tubule, poly (styrenesulfonic acid sodium) (PSS, a polyanion) was dissolved in the water phase, while NH2-PDMS-NH2 (N-PDMS, a positively charged ligand) was dissolved in the oil phase. The aqueous solution was jetted into the oil phase at a rate of 90 \mu L min-1 with a 0.60 mm bore needle. At the oil-water interface, the oppositely charged ligands rapidly interacted to form what we term soft nanoparticle surfactants (sNPSs) (Fig. 1a)21, as evidenced by the reduction of the interfacial tension (IFT), < 10 mNm-1 (Fig. 2a). The binding energy of the sNPSs is significantly increased due to the multiple interaction sites of the PSS and the N-PDMS, stabilizing the nonequilibrium tubular shape of the liquid interface by the rapid jamming of sNPSs at the interface22. With increasing ligand content, the IFT decreases to a level insufficient to counteract gravity, causing pendant drop break-up, preventing long-term measurement. By adjusting the concentrations of PSS and N-PDMS to 3 wt.% and 3 wt.%, respectively, the jetted water evolved from semi-spherical to tubular shape (Fig. 2b), enabling all-liquid 3D printing and the preparation of the RAOFs.

The numerical aperture (NA), which defines the acceptance angles of the RAOFs, was calculated as NA = 0.4923, offering flexibility to couple the RAOFs into an internet system. To further benefit the fabrication of RAOFs and make them adaptable to practical applications, the parameter domain of all-liquid 3D printing for RAOFs was studied. By varying the concentration of interfacially active components, printing speed, nozzle diameter, and liquid flow rates, diameters of RAOFs ranging from ~300 \mu m to 1.7 mm were successfully fabricated (Supplementary Fig. 5, Supplementary Note 1). The accessible range is mainly limited by nozzle geometry, liquid viscosity, and IFT, as well as the tendency of fibers to break up due to Plateau–Rayleigh instability; this is mitigated by interfacial jamming induced by interfacial assembly, which mechanically stabilizes the fibers and preserves their tubular geometry18. The stability of RAOFs arises from the combined effects of interfacial elasticity, tension, capillarity, and viscous damping of the continuous phase. Even with a density difference between the core and oil, fibers smaller than a critical radius maintain a circular cross-section. High continuous-phase viscosity and nanoparticle-stabilized interfaces further enhance stability, enabling both two- and three-dimensional fiber designs. Quantitative estimates of these factors provide guidance for designing robust liquid fibers under gravity (Supplementary Note 2, Supplementary Fig. 6).

With the flexible all-liquid 3D printing method, we fabricated complex-RAOF patterns that can be reconfigured (Fig. 2c). However, the microscopic structure of the oil-water interface shows roughness in the sNPSs at the nanoscale (Fig. 2d), and the microscale, due to imperfections in the assemblies (Supplementary Fig. 7, Fig. 2e.). As a result, light scattering and leakage occur and contribute to the visibility of the light propagation (Fig. 1e). Additional leakage, as would be expected, was seen at high-curvature bends where the incidence angle of the light exceeded the critical angle (also seen with commercial optical fibers) (Supplementary Fig. 8). The adsorption and jamming of nanoparticles increase interfacial roughness (S ~ 17 nm), which enhances light scattering and optical loss compared to smooth quartz fibers; therefore, interfacial engineering to reduce roughness is essential for achieving low-loss all-liquid optical fibers. Interfacial wrinkles, resulting from the relaxation of the assemblies, significantly increase leakage and attenuate transmitted light, making their elimination essential for optimizing fiber performance. To mitigate wrinkle formation, the oil phase was initially replaced with a high-viscosity silicone oil (60,000 cSt) that slowed their development. As shown in Supplementary Fig. 9a and 9b, imperfections, such as seams on the surface of the RAOF, caused wrinkles to form normally to the axis of the RAOF24. These wrinkles were attributed to over-saturated interfacial assemblies that produced in-plane stress. We then introduced an interfacial relaxation strategy by reducing the glucose concentration in the aqueous phase, which increased interfacial fluidity and effectively eliminated wrinkles, thereby suppressing scattering and markedly improving transparency (Supplementary Fig. 9c, d)25. Interestingly, a systematic investigation revealed that the output light intensity does not follow a simple, monotonic dependence on glucose concentration. This behavior originates from a trade-off between two competing effects: (i) reduced glucose concentration lowers the refractive index difference with the oil phase, weakening total internal reflection and thus decreasing transmission, while (ii) the lower viscosity enhances interfacial relaxation, eliminating wrinkles and reducing scattering. As a result, at an optimal glucose concentration of ~60 wt.%, these competing factors are balanced, yielding wrinkle-free RAOFs and an enhancement of transmitted intensity (Supplementary Fig. 10). This trade-off provides valuable guidance for tuning interfacial morphology and optimizing RAOF performance. The attenuation of the printed RAOF was determined using the cut-back method, yielding ~0.631 dB cm-1 (Supplementary Fig. 11a). To provide a qualitative analysis of the signal and offer visual information on digital transmission, which serves as a first-order approximation of signal-to-noise ratio, clock timing jitter, and skew, the system’s eye diagram was tested (Supplementary Note 3)26. Eye diagrams measured at multiple positions along the same fiber show a reduction in eye-opening from 0.0387 V to 0.0243 V (Supplementary Fig. 11b, c), consistent with the decrease in received optical power and signal-to-noise ratio with increasing fiber length, while other metrics such as timing jitter and eye width remain nearly unchanged. Although the loss is higher than in conventional silica fibers, it is comparable to recently reported polymer-based fibers. Importantly, RAOFs can be printed in situ, repaired, and dynamically reconfigured, enabling versatile local interconnects. These results demonstrate that Gbps-level data transmission is achievable over short distances, confirming the practical potential of RAOFs for adaptive and reconfigurable optical communication networks.

Real-time communication by reconfigurable all-liquid optical fibers
The propagation of light along the RAOF enables its use in real-time communication systems. To evaluate the feasibility of the RAOF for telecommunication, it was integrated into an Ethernet platform, replacing traditional commercial optical fibers (Fig. 3a and Supplementary Fig. 12). And we used eye diagram to reveal the evolution of the communication performance at data rates ranging from 200 Mbps to 1 Gbps (Fig. 3b, c, Supplementary Fig. 13). As the data rate increases, the width and height of the eye diagram diminish, indicating a decrease in the signal-to-noise ratio. Nevertheless, the stable operation at 1 Gbps verified the feasibility of using the RAOF, demonstrating its capability to meet the basic requirements of most communication scenarios. In our current setup, the achievable data rate and bandwidth are primarily constrained by hardware factors such as the intrinsic bandwidth of the receiver and coupling efficiency. For example, by replacing the APD with a photodiode (PD), we increased the receiver bandwidth and achieved 1.28 Gbps transmission with a clearer eye diagram (Supplementary Fig. 14). This indicates that further optimization of system hardware could effectively enhance performance and enable future advancements in this technology. To further demonstrate the performance of the RAOF in a practical optical communication system, we used the Ethernet platform operating at 100 Mbps to showcase the practical use of RAOF for information transmission. Data communication speeds ranging from 1 kbps to 10 Mbps were easily achieved (Supplementary Figs. 15, 16), indicating that the RAOF can efficiently transmit light for data communication. With a certain input signal (Supplementary Fig. 17a) when the receiver was shifted from the free space optical path by a distance (~5.5 mm) and an angle (~34°) (Supplementary Fig. 17b), the loss of light causes a loss of communication signal (Supplementary Fig. 17c). However, by printing an arc-shaped RAOF to reconnect the transmitter and receiver (Supplementary Fig. 17d), the signal was restored without signal loss (Supplementary Fig. 17e), demonstrating system flexibility and ability to operate on demand.

High bandwidth is essential for practical applications, such as high-definition television (HDTV) streaming, which requires speeds of 5-8 Mbps. Based on our previous results, this requirement can be easily achieved using RAOFs. Motivated by this potential, we integrated RAOFs into an HDTV streaming setup. The 94/97-Mbps up/download speeds capped by our network equipment and protocols, and 25-ms network latency floored by the distance to the speed test center (Supplementary Fig. 18), indicate that the liquid fiber did not bring a significant performance penalty and could fully support HDTV streaming. Furthermore, the signal received at the output end matched the source signal (Fig. 3d), validating its suitability for real-time communication. The corresponding eye diagram also indicates the consistency between the source and receiver signals (Fig. 3e, Supplementary Fig. 19). Internet browsing using the RAOF demonstrated seamless performance with no noticeable delay (Supplementary Video 2). Finally, we showcased the potential of RAOFs for a live online video meeting. By integrating the RAOF into the communication system, we successfully established a stable connection between different countries, supporting HDTV streaming (Fig. 3f, Supplementary Video 3). These results demonstrate that the RAOF can be used as an alternative for optical fibers in practical applications, including high-speed internet and online video conferencing.

Liquid nature of reconfigurable all-liquid optical fibers
Quartz optical fibers are inherently brittle, making them prone to fracture. This brittleness often requires the replacement of damaged fibers, as repair techniques such as fusion splicing are not always practical in UWC27,28. And the coupling between fixed attachments and the quartz optical fibers also imposes limits on the practical application in underwater environments. In contrast, RAOFs, due to their liquid nature, offers significant advantages in terms of flexibility, ease of repair, structural reconfiguration, and the accessible coupling between fixed attachments and the RAOF29–31. Despite being printed into a nonequilibrium shape controlled by an interfacial solid-like film, RAOF retains its liquid state, allowing for on-demand adaptation to complex environments.

One of the most important benefits of the liquid state of RAOF is its inherent self-healing capability in water environments. When fractured, the fiber can be repeatedly repaired or even self-repair, restoring the signal link and minimizing downtime. In a practical demonstration, the RAOF was used to link two computers via a wide-area network (WAN), with the signal transmission initially functioning well (Fig. 4a, b). Upon breaking the RAOF (Fig. 4c, d), the communication link was disrupted, causing the signal to cease, halting the video stream, and resulting in a loss of synchronization (Supplementary Video 4). At the breaking point, the sNPSs rapidly self-assembled, sealed the broken ends, and light propagation through the fiber was cut.

To repair the break, a simple welding process was conducted by injecting an additional water phase into the fractured region, reconnecting the broken ends, and restoring the signal link between the two computers (Fig. 4e-f). This easy repair is rather convenient for the UWC system, which is superior to the traditional quartz optical fibers. Although there was some increased light scattering near the break due to defects (Fig. 4e), the functions remained unaffected, and the fiber’s performance was identical to its pre-break state. Notably, the connection speed after repair shows no significant attenuation compared with that before the breakage (Supplementary Fig. 20). The video stream resumed, and the link between the computers was fully restored (Supplementary Video 4). This demonstration highlights the remarkable ability of RAOFs to self-heal and recover, making it a viable and efficient solution for maintaining real-time communication links.

Structural design of RAOF
Optical waveguide devices are integral to optical communication and computing systems, serving the essential function of manipulating light beams for separation and combination. These devices rely on various optical effects, such as the electro-optical, thermo-optical, and magneto-optical effects, to control the optical field and transfer information into the optical domain. Reconfigurable optical waveguide arrays have become increasingly significant in the fields of optical switching and the development of programmable optical computing chips, offering flexible control over optical signals32,33. However, traditional optical waveguide devices are typically formed in photonic integrated circuits, photolithographically on a 2-dimensional plane of materials like lithium niobate, silicon, or silicon nitride. Once formed, the optical waveguide’s topology becomes fixed. It is possible to achieve limited changes in waveguide topology through electrical34 or thermal35 control; however, the range of these changes remains confined to a subset of the pre-formed structures. In other words, all possible configurations are already determined during the initial fabrication, and electrical or thermal control can only transition the topology from one predefined state to another. The fluidity of the RAOF not only facilitates self-repair but also enables reconfiguration in a scalable and transformable manner, distinguishing RAOFs from conventional reconfigurable optical waveguides14,36.

One such example is an optical splitter. By using all-liquid 3D printing, the RAOF can be spatially programmed to generate a new branch from the original fiber, hence forming a new Y-Branch. The bifurcation can be established at any location along the fiber to provide a user-defined functionality. Further splitting at more points can turn RAOF paths into any desired structures, without pre-design and fabrication of a superset waveguide topologies, and, thus, with remarkable freedom (Fig. 4g). With this approach, we fabricated RAOF structures in situ to split light waves into distinct channels (denoted as CH 1 and CH 2) (Fig. 4h, i). This reconfiguration enables versatile channel switching and on-demand signal selection (Fig. 4j). By positioning the receiver at different channels, the transmitted signal can be switched seamlessly (Fig. 4j, Supplementary Figs. 21 and 22, and Supplementary Video 5), demonstrating the adaptability of the reconfigurable design. Such a structurally scalable, transformable, and reconfigurable RAOF is superior to the traditional quartz optical fibers or reconfigurable photonic integrated circuits, offering the possibility to adapt the RAOF to various complicated working conditions and satisfy on-demand shape changes.

The concept of 3D reconfigurable optical waveguide design offers a new paradigm. Not only can the shape and spatial positioning of the optical waveguide be fully reconfigured, but the RAOF can also manipulate the internal light field. For traditional optical fibers and photonic integrated circuits operation, an additional switch should be coupled into the system to control signals switching and on-off control, which requires significant effort to logically design and implement. In contrast, with RAOFs, dynamic switching between channels or toggling of the signal (on and off) was easily achieved by introducing a ferrofluid droplet into the channels (Fig. 4k). The ferrofluid droplet can be remotely controlled to relocate freely inside the RAOF, acting as a switch to block or release the light signal across the tubule (Fig. 4l, m, Supplementary Video 6). The signal can thus be controlled as needed (Fig. 4n). No persistent power control is needed to maintain the switched status, as in Mach-Zehnder interferometric switch34,35. And again, the switch or block can be located arbitrarily along the fiber. Even after multiple reconfigurations, the received signals remained consistent with the source signals (Supplementary Fig. 23), confirming the structural and functional reliability of the RAOF system. The manipulation method is not limited to magnetic forces; it can be extended to other mechanisms, such as acoustic techniques. Moreover, implanting droplets into RAOF can be done at arbitrary positions and is far more convenient than conventional optical waveguides. The implant could stimulate novel and diverse effects in and by the lightwave, for instance, polarization effect, nonlinearity, and particle manipulation. This opens new opportunities for further investigation.

In summary, we successfully fabricated a RAOF for real-time communication using all-liquid 3D printing, leveraging the unique properties of liquid interfaces. The design is based on two key principles: (1) the liquid interface as a platform for interfacial self-assembly of charged polymer ligands, enabling the fabrication of liquid tubules; and (2) the intrinsic refractive index difference at the water-oil interface, facilitating total internal reflection. The self-assembly process stabilizes the RAOF structure, achieving diameters as small as 300 \mu m and enabling light propagation for real-time communication at speeds up to 1 Gbps. Due to its liquid nature, the RAOF exhibits exceptional softness, self-healing capabilities, and on-demand reconfigurability, making it adaptable to complex environments and resilient under impact. Moreover, the RAOF affords the on-demand manipulation of the signal transmitting anywhere inside the fiber, offering promising potential for the future development of optical fiber for on-demand operation. This innovation offers valuable insights for future implementations in underwater optical communication, where appropriate refractive index contrast and immiscible aqueous systems could be employed.

Methods
Materials
Aminopropyl terminated polydimethylsiloxane (N-PDMS, Mn ~ 3 kg mol-1, Gelest), Poly(styrenesulfonic acid) sodium salt (PSS, M.W. 7000, Thermo Scientific), Silicone oil (1000 cSt, Aladdin, China), Silicone oil (60,000 cSt, Aladdin, China), D-(+)-Glucose (AR, Aladdin, China), DIW was obtained from Milli-Q system; Polylactic Acid filament for 3D printing of the homemade mode was used as received from 3DMart.

The preparation of a compatible water phase and oil phase
The operating basis of optical fiber is the total internal reflection of light at the interface between the fiber core and cladding. Herein, the prerequisite for realizing all liquid optical fibers is to manipulate the RID across the liquid core-cladder interface. In this work, the water phase is used as the fiber core while silicone oil is chosen as the cladding. To increase the RI of the water core, glucose is used to adjust the RI of the water core37. In detail, glucose was dissolved in water with various weight percentages, as shown in Supplementary Fig. 2a, and to optimize the RID, the 77.8 wt.% group was used as the water core. Another precondition is to realize the interfacial self-assembly to obtain a structured liquid, which can be used to prepare ALFs38. Here, PSS, a negatively charged polyanion, and N-PDMS, a positively charged ligand upon protonation, were dissolved in the water phase and oil phase, respectively. Due to their oppositely charged state, they will assemble at the oil-water interface through electrostatic interaction, forming NPS. To study the influence of ligand content on the IFT, the content of PSS and N-PDMS was adjusted, i.e., the PSS content was varied from 1.1 wt.% to 5 wt.%; N-PDMS content in oil phase was varied from 2 wt.% to 4 wt.%. The IFT was measured using a typical pendant drop method with a tensiometer39, in which a droplet of the water phase was suspended in the oil phase and imaged to extract the interfacial curvature.

3D printing of the all-liquid optical fiber
A commercially available 3D printer (Snapmaker A350T) is used to print the water solution (ink) in the oil solution (bath), which is demonstrated in Fig. 1a. For suitable printing, the ink contains [glucose] = 77.8 wt.% and [PSS] = 3 wt.%, while the bath contains the [N-PDMS] = 3 wt.%.

In-situ atomic force microscopy
The in-situ AFM imaging was carried out using a typical protocol40. First, the water phase and the oil phase are synthesized according to the suitable component for 3D printing, i.e., water phase contains [glucose] = 77.8 wt.% and [PSS] = 3 wt.%, oil phase contains [N-PDMS] = 3 wt.%. Silicon wafers with <100> orientation were cut into square pieces 0.5 cm \times 0.5 cm and later glued to a magnetic puck using epoxy, forming the substrates. All components, including the substrates, AFM tip holder, and AFM tips (Biolever mini AC40TS, Olympus), were cleaned in a UV Ozone tool for 10 minutes. A tiny drop (~100 nL) of the oil is dipped onto the substrate and subsequently subjected to degassing by using a vacuum chamber. Then the sample was placed on the sample stage of the Cypher ES scanner (Oxford Instruments). In the meantime, ~100 \mu L water phase was added to fully cover the oil droplet. Notably, due to the high viscosity of both water and oil phases, the density mismatch between oil and water phases is neglected, and the oil droplet does not float up during the experiment. In this manner, the water-oil interface was formed and was ready for characterization. The in-situ AFM imaging experiments were carried out in AC mode, and the scan range was set to 20 \times 20 \mu m in lateral size. Before the scanning, the interface was settled for 30 minutes to allow the interfacial self-assembly at the oil-water interface.

Real-time communication by RAOF
To assess the performance of liquid optical fiber in a practical communication system, we have developed a 100 Mbps Ethernet platform. As shown in Fig. 3a, we use a personal computer (PC, DELL workstation) as the network receiver, connecting to the Internet via a 100 Mbps intensity modulation-direct detection (IM-DD) fiber optic link. In the downlink of the Ethernet network, an RJ45 twisted pair cable connects the Internet to optical transceiver 1 (LNK-M3011-SFP). This transceiver converts the Ethernet-protocol signal into a gigabit transceiver (GTX) protocol optical signal that can be transmitted over the fiber optic link. The core components of the fiber optic link are a semiconductor laser (QSI, QL68J6SC) and an AC-coupled drive circuit on the transmitting side41, and an avalanche photodiode (APD, Thorlabs APD430A2/M) on the receiving side. The driver board supplies bias current and amplified AC signals to the semiconductor laser. The semiconductor laser emits light at a central wavelength of 650 nm, which passes through a plastic optical fiber (POF/L1FC-FC) into the core of the liquid fiber. The plastic optical fiber has a core diameter of 1000 \mu m and a large numerical aperture, which allows for better coupling with the liquid optical fiber. The light is transmitted through total reflection in the liquid fiber. At the receiving end, the light from the liquid fiber is coupled into the plastic optical fiber, which is connected to the APD. Operating in the visible light band, the APD converts the received optical signal into an electrical signal for transmission to the receiving side of optical transceiver 2 (LNK-M3011-SFP). To address the power mismatch among the optical transceiver module, the input signal of the driver board, as well as the output signal levels of the APD, we added a tunable gain amplifier between the two optical transceivers and the fiber optic link. This amplifier module adjusts the input and output power levels of the fiber optic link. The tunable gain amplifier, consisting of an electrical attenuator (RBS-70-3-2) and a fixed-gain electrical amplifier (MPA-10-40), provides a gain adjustment range of -30 dB to 40 dB. To monitor the received signal of the downlink, we introduce a branch to an oscilloscope through a 1 \times 2 power splitter (RS2DC60-S) placed between the APD and optical transceiver 2.

In the uplink, we use coaxial cables (T1-SMAMAMAM-1m) to connect the transmitting end of optical transceiver 2 to the receiving end of optical transceiver 1. By downloading data from the Internet through the downlink, we demonstrated that real-time data transmission is achievable over the liquid fiber link. To the best of our knowledge, this is the first real-time Ethernet system based on pure liquid fibers to support standard Ethernet services, including web browsing, video downloading, and online web conferencing.

Measurements of eye patterns
To evaluate the performance of the optical fiber communication system, we utilized a high-speed arbitrary waveform generator (AWG, Keysight M8190A) and a sampling oscilloscope (Agilent 86116C Opt. 040) to measure the eye diagrams across various data rates. The AWG generated a pseudo-random sequence modulated using on-off keying with non-return-to-zero (OOK-NRZ), which was subsequently loaded onto the laser source after amplification by the tunable gain amplifier and transmitted through the optical fiber link. Considering the bandwidth limitation of the APD at 400 MHz, a higher-bandwidth PIN-type photodiode (PD, 818-BB-21A, with a 1.2 GHz bandwidth) was employed to provide enhanced system performance evaluation. Eye diagram measurements were conducted across data rates ranging from 0.2 to 1 Gbps, with an increment step of 0.2 Gbps. The experimental results indicate that, at rates below 600 Mbps, the eye diagrams are clear, with minimal signal distortion. However, at higher data rates, slight signal jitter was observed, leading to minor degradation in signal integrity. These findings demonstrate that the optical communication system, utilizing pure liquid fiber, has shown preliminary communication capabilities and is compatible with current optical networks. This indicates considerable potential for its integration into future reconfigurable optical communication infrastructures.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "Zhao et al. demonstrated the use of interfacial assembly and jamming of soft amphiphilic species at the liquid-liquid interface\nto construct all-liquid optical fibers. Traditional optical communication strongly relies on glass fibers due to their excellent\noptical properties and extremely high communication bandwidth. Fiber optics have dominated the modern communication\nmarket for decades. While glass fiber-based optical communications have many advantages, the solid nature of glass\nmakes it less feasible in certain complex and dynamic information scenarios. For instance, glass fibers lack post-setup\nadaptability, such as reconfigurable topological communication networks. Addressing this limitation has significant impact\nand is very valuable. In this manuscript, the authors propose the idea of generating optical fibers solely made of liquids. The\nreviewer finds the idea highly novel, as it completely opens a new avenue beyond traditional solid glass fiber\ncommunication and has the potential to generate many practical impacts. The authors realized these all-liquid fibers through\nan all-liquid 3D printing technique, which relies on two interactive species that assemble at the liquid-liquid interface. These\ntwo species can pack closely at the interface, effectively jamming it, allowing one liquid to be shaped within another\nimmiscible liquid (in this case, forming a liquid tube that acts as an all-liquid optical fiber). The authors have done an\nexcellent job demonstrating the feasibility of their all-liquid fibers. The reviewer finds the realization of online video meetings\nand a connection speed up to 1 Gbps to be fantastic. More importantly, the authors demonstrate the reconfigurability and\ndynamic control of the communication topology through a 3D printer and ferrofluids at the physical setup level. This\nhighlights the adaptability and functionality of their Reconfigurable All-Liquid Topological Optical Fibers (RATOF). Overall,\nthe reviewer feels the manuscript is well-written, the concept of RATOF is highly innovative, and the demonstration of\nreconfigurability and adaptability is promising. Therefore, the reviewer strongly supports its publication in Nature\nCommunications.\nThe following are some detailed comments and suggestions to further improve the quality of the final version of the\nmanuscript:\n1.In Figure 2, the authors discuss how different concentrations of PSS and N-PDMS affect the interfacial tension, influencing\nthe 3D printing process, such as the width of the all-liquid fiber. It would be helpful to elaborate on how these variations\nimpact the optical performance of the fibers.\n2.The manuscript mentions that wrinkles significantly affect light transmission in all-liquid fibers. Reducing glucose\nconcentrations can eliminate wrinkles, thereby enhancing light transmission performance. It would be valuable to include\nmore data and discussion on this topic, such as the effects of different glucose concentrations.\n3.The authors demonstrate the advantage of all-liquid optical fibers in terms of ease of repair, as shown by the resumption of\nonline video after repairing a broken section. It would strengthen the manuscript to include the connection speed after repair\nto better highlight the quality of the restoration.\n4.The manuscript successfully demonstrates a 1 Gbps connection speed. It would be beneficial to discuss potential factors\nthat could further improve performance and how these could be optimized. This would help readers envision future\nadvancements in this technology.\n5.While the authors have demonstrated the merits of RATOF, including its ability to establish an internet connection\n(Supplementary Video 2) and perform signal switching (Supplementary Video 5), the quality of these videos could be\nimproved to better convey RATOF's functionalities. Considering the importance of these videos in demonstrating the system,\nboth their content and execution should be refined to provide readers with a clearer understanding and a more engaging\nviewing experience.\n6.The concept of RATOF could inspire people from various fields. Therefore, it is suggested that the authors provide detailed\nsetup photos to assist researchers from diverse disciplines who are interested in this work. This will enable the efficient\nreplication of experiments and further exploration of RATOF's broader applications.\n7.The interfacial tension test only holds ~700s for 1.1wt% PSS, 4wt% N-PDMS” in stead of ~1200s as others, why?", "reviewer_2": "The manuscript reported the fabrication of a novel reconfigurable all-liquid topological optical fiber (RATOF) using structured\nliquid formation. By using 2 immiscible liquids, where the core aqueous phase had a higher, tunable refractive index, total\ninternal reflection can be achieved. The high interfacial tension of the 2 liquids favored formation of individual droplets rather\nthan a tubule structure. Therefore, the authors applied 2 polyelectrolyte and the self-assembly of them at the interface\nsuccessfully reduced the interfacial tension to around 1 mN m, which allowed tubule formation in the printing process. The\nformation of RATOF was well-characterized and various interesting aspects regarding their RATOF were also demonstrated\nwith adequate experiments and setups. Although, based on the current experimental data about the properties of the\nRATOF, the production and application of it might not be feasible in the near future, this manuscript has successfully\ndemonstrated new insights in future optical fiber designs. Nevertheless, some of the experimental data are clear enough and\nthey should be replaced by better ones and other revisions are suggested. The following are comments and suggestions for\nthe authors.\n1. Page2, line 60: why soft optical fibers are primarily used as sensors rather than for telecommunication? The authors might\nconsider elaborate more so that readers that are not very familiar with optical fiber can understand more about the weakness\nof soft optical fibers in practical application, where RATOF might also experience similar problems.\n2. From the video demonstrations, the RATOF should be immersed in a bath of silicone oil. Therefore, the illustration in\nfigure 1a is a bit misleading.\n3. At the curvature shown in figure 1e, did most of the light leak?\n4. The authors should include the IFT data for 3% PSS with 3% NPDMS as it is the condition for the RATOF printing.\n5. At such low IFT, it seems that the Laplace pressure is very low and not enough to maintain a circular cross section of the\nRATOF. Will the RATOF collapse easily under stress from the outer phase?\n6. Could the authors provide the characterization of the signal quality based on the length of the RATOF?\n7. For the RATOF repairing experiment, the video did not show how it was broken and how it was repaired clearly. The\nauthors should take the video at a better angle to clearly show the breaking and more importantly, the repairing of RATOF.\n8. For figure 4J and 4K, it is better to include a video showing the movement of the ferrofluid droplet. It is quite interesting that\nthe ferrofluid droplet did not break the RATOF when it moved in and out of it.", "reviewer_3": "The authors of this paper present the realization of liquid optical fibers formed by stabilizing a water oil-interface by means of\nin-situ assembly. The method for interface stabilization has been pioneered by the Russel group in previous studies, but this\nmanuscript reports an impressive practical demonstration of a potential application in telecommunication. The authors\nclearly show that their optical fibers can work as low-loss, broadband connectors between conventional optical fibers and\nallow for standard connectivity supporting video feed and data transfer. The authors also show that their optical fibers,\nbecause made exclusively from liquid components, can be easily repaired and reconfigured.\nI found the demonstration very impressive, but I would ask the authors to provide additional details to the manuscript to\nprovide the quantification of essential aspects that can be used as guidelines by others, as well as to provide a deeper\nunderstanding of the materials used.\nAfter addressing these issues, I would be happy to recommend publication.\nMain comments:\n- How does the RI change in the presence of surfactants in the two phases? The authors only report the variation of RI as\nfunction of glucose concentration in the SI.\n- How does the presence of adsorbed NPs change the scattering of light at the interface? How does the roughness of the\ninterface reported in Figure 2d compare to the one of quartz fibers? What is the requirement for the roughness of the\ninterface to obtain a low loss compatible with applications?\n- What is the density difference between the two liquids and how does that affect the geometry of the fibers that can be\nprinted? I presume that the glucose-water mixtures are significantly heavier than the oil. Does this mean that only two-\ndimensional fiber designs resting on the bottom of a container can be realized? Is there an option to go in the third\ndimension?\n- Along the same lines, how does the interfacial elasticity compare to weight difference? Providing quantitative estimates of\nthese factors would be informative to guide the design of different systems.\n- What is the smallest and largest fiber diameter that can be printed? What are the limiting factors?\n- What is the loss per unit length? Based on these numbers, how do the liquid fibers compare to glass ones? Is there any\nreal potential for communication or should the liquid fibers be considered only useful for local connections which can be\nrepaired and reconfigured?\nMinor/general comments:\n- I do not understand the meaning of the choice of the term “topological” in the naming of the fibers. If anything, these can be\ncalled “topologically reconfigurable” but I think that “reconfigurable” suffices. I would not know what a topological fiber is.\n- The authors should also elaborate further on the notion of underwater communication and how their technology applies to\nit, given that the optical fiber is immersed in an oil bath.\n- There are many typos along the text and figure captions. There are also some sweeping statements such as “The concept\nof 3D reconfigurable optical waveguide design is groundbreaking” (line 326) or “This opens up tremendous new research\nopportunities” (line 346), which I leave to the editor’s judgement.\n- I found the supplementary video S2 not very useful and not quite appropriate, given that it shows the arbitrary browsing and\nshows personal information such as browsing history etc. The videos showing the connectivity in a lab environment are, in\nmy opinion, much more appropriate and effective. The video with the online meeting is also only mildly relevant. I would in\ngeneral think that the authors should carefully consider the relevance, content and format of the video (image and sound)."}, "author_response": "We thank both reviewers for their kind and positive comments. The following is a\npoint-by-point response to both reviewers’ comments and a list of changes made to the\nrevised manuscript.\nNote to Reviewers:\nFollowing Reviewer #3’s Comment 7, we have replaced the term “Reconfigurable\nAll-Liquid Topological Optical Fibers (RATOFs)” with “Reconfigurable All-Liquid\nOptical Fibers (RAOFs)” throughout the manuscript and the response letter for clarity\nand consistency. For detailed discussion, please refer to Comment 7 from Reviewer #3.\n----------------------------------------------------------------------\nReport of Reviewer #1\n----------------------------------------------------------------------\nOverall Comments:\nZhao et al. demonstrated the use of interfacial assembly and jamming of soft\namphiphilic species at the liquid-liquid interface to construct all-liquid optical fibers.\nTraditional optical communication strongly relies on glass fibers due to their excellent\noptical properties and extremely high communication bandwidth. Fiber optics have\ndominated the modern communication market for decades. While glass fiber-based\noptical communications have many advantages, the solid nature of glass makes it less\nfeasible in certain complex and dynamic information scenarios. For instance, glass\nfibers lack post-setup adaptability, such as reconfigurable topological communication\nnetworks. Addressing this limitation has significant impact and is very valuable. In this\nmanuscript, the authors propose the idea of generating optical fibers solely made of\nliquids. The reviewer finds the idea highly novel, as it completely opens a new avenue\nbeyond traditional solid glass fiber communication and has the potential to generate\nmany practical impacts. The authors realized these all-liquid fibers through an all-liquid\n3D printing technique, which relies on two interactive species that assemble at the\nliquid-liquid interface. These two species can pack closely at the interface, effectively\njamming it, allowing one liquid to be shaped within another immiscible liquid (in this\ncase, forming a liquid tube that acts as an all-liquid optical fiber). The authors have\ndone an excellent job demonstrating the feasibility of their all-liquid fibers. The\nreviewer finds the realization of online video meetings and a connection speed up to 1\nGbps to be fantastic. More importantly, the authors demonstrate the reconfigurability\nand dynamic control of the communication topology through a 3D printer and\nferrofluids at the physical setup level. This highlights the adaptability and functionality\nof their Reconfigurable All-Liquid Topological Optical Fibers (RATOF). Overall, the\nreviewer feels the manuscript is well-written, the concept of RATOF is highly\n1\ninnovative, and the demonstration of reconfigurability and adaptability is promising.\nTherefore, the reviewer strongly supports its publication in Nature Communications.\nThe following are some detailed comments and suggestions to further improve the\nquality of the final version of the manuscript:\nAuthor response:\nWe appreciate the reviewer's positive feedback on our work. We particularly thank\nthe reviewer for the insightful comments. Please find our responses below.\nComment 1. In Figure 2, the authors discuss how different concentrations of PSS and\nN-PDMS affect the interfacial tension, influencing the 3D printing process, such as the\nwidth of the all-liquid fiber. It would be helpful to elaborate on how these variations\nimpact the optical performance of the fibers.\nAuthor response:\nWe thank the reviewer for the suggestion.\nWe fabricated RAOF with core diameters ranging from ~300 μm to 1.7 mm using\nall-liquid 3D printing, resulting in a multimodal optical fiber. The number of guided\nmodes M can be estimated as1:\nM≈\nV2\n, V=\n2πa\nNA\n2 λ\nWhere a is the core radius, λ is the operating wavelength, and NA is the numerical\naperture. A larger diameter (a) or higher NA increases the number of modes, improving\ncoupling efficiency by making the fiber more tolerant to alignment errors and variations\nin the incident beam. Consequently, the RAOF diameter strongly influences fiber-to-\nfiber coupling efficiency. As shown in Supplementary Fig. 12, in the present system,\noptimal coupling requires matching the RAOF diameter with that of the commercial\nplastic optical fiber, ensuring efficient light input into the system. However, an\nexcessively large core diameter can compromise the operational stability of RAOF in\npractical applications. Therefore, a balance between coupling efficiency and system\nstability must be considered to achieve optimal performance. In this condition, the\ndiameter width plays a key role in optimizing the coupling of RAOF into the\ncommunications system. We have added additional discussion to the manuscript.\nChange 1:\nMain text, page 6, lines 169-171.\n“By varying the concentration of interfacially active components, printing speed,\nnozzle diameter, and liquid flow rates, diameters of RAOFs ranging from ~300 µm to\n1.7 mm were successfully fabricated”\nComment 2. The manuscript mentions that wrinkles significantly affect light\ntransmission in all-liquid fibers. Reducing glucose concentrations can eliminate\nwrinkles, thereby enhancing light transmission performance. It would be valuable to\n2\ninclude more data and discussion on this topic, such as the effects of different glucose\nconcentrations.\nAuthor response:\nWe thank the reviewer for this constructive suggestion. To systematically\ninvestigate the influence of glucose content on light transmission, we measured the\noutput light intensity (Power) as a function of glucose concentration. As shown in\nSupplementary Fig. 10, the output intensity does not vary monotonically with glucose\ncontent; instead, it reaches a maximum at around 60 wt.%. This behavior arises from\ntwo competing effects: (i) lowering glucose reduces the refractive index difference with\nthe oil phase (Supplementary Fig. 2a), tending to decrease transmitted power, and (ii)\nlowering the water-phase viscosity enhances interfacial relaxation and eliminates\nwrinkles (Supplementary Fig. 9), thereby suppressing scattering losses. The interplay\nof these effects explains the observed non-monotonic trend and provides insight into\nhow interfacial morphology can be tuned to optimize RAOF transmission. We have\nexpanded our discussion in the manuscript.\nChange 2:\nMain text, page 8, lines 214-227.\n“We then introduced an interfacial relaxation strategy by reducing the glucose\nconcentration in the aqueous phase, which increased interfacial fluidity and effectively\neliminated wrinkles, thereby suppressing scattering and markedly improving\ntransparency (Supplementary Figs. 9c and 9d). Interestingly, a systematic investigation\nrevealed that the output light intensity does not follow a simple, monotonic dependence\non glucose concentration. This behavior originates from a trade-off between two\ncompeting effects: (i) reduced glucose concentration lowers the refractive index\ndifference with the oil phase, weakening total internal reflection and thus decreasing\ntransmission, while (ii) the lower viscosity enhances interfacial relaxation, eliminating\nwrinkles and reducing scattering. As a result, at an optimal glucose concentration of\n~60 wt.%, these competing factors are balanced, yielding wrinkle-free RAOFs and an\nenhancement of transmitted intensity (Supplementary Fig. 10). This trade-off provides\nvaluable guidance for tuning interfacial morphology and optimizing RAOF\nperformance.”\nSupplementary information, page 13, Supplementary Fig. 10.\n3\n“Supplementary Fig. 10. The change of detected light intensity at the output end of\nRAOF when decreasing the content of glucose in the water phase. The dashed line is a\nfitted curve to guide the eye. Values in the figure represent the mean, and the error bars\nrepresent the SD of the three measured values of each sample (n = 3). The power of all\nreplicate samples was measured by an identical power meter.”\nComment 3. The authors demonstrate the advantage of all-liquid optical fibers in terms\nof ease of repair, as shown by the resumption of online video after repairing a broken\nsection. It would strengthen the manuscript to include the connection speed after repair\nto better highlight the quality of the restoration.\nAuthor response:\nWe thank the reviewer for this insightful suggestion. In the revised manuscript, we\nhave added measurements of the data transmission speed before and after the repair,\nas shown in Supplementary Fig. 20. The results indicate that the connection speed after\nrepair shows no significant attenuation compared with that before the breakage. In fact,\nthe measured download speed after repair appeared slightly higher, which can be\nattributed to normal network fluctuations rather than any enhancement of the fiber\nperformance. In other words, the breaking and subsequent repairing of the all-liquid\noptical fiber does not affect its communication capability. This provides further\nevidence of the robustness and reliability of the repairing strategy.\nChange 3:\nMain text, pages 11-12, lines 325-326.\n“Notably, the connection speed after repair shows no significant attenuation compared\nwith that before the breakage (Supplementary Fig. 20).”\nSupplementary information, page 24, Supplementary Fig. 20.\n4\n“Supplementary Fig. 20. Comparison of the connection speed before breakage and\nafter repair.”\nComment 4. The manuscript successfully demonstrates a 1 Gbps connection speed. It\nwould be beneficial to discuss potential factors that could further improve performance\nand how these could be optimized. This would help readers envision future\nadvancements in this technology.\nAuthor response:\nWe thank the reviewer for this insightful suggestion. While the optical loss of our\nliquid fibers is higher than that of silica fibers, it does not limit the achievable data rate\nor bandwidth. In our current setup, the performance is mainly constrained by hardware\nfactors such as the avalanche photodiode (APD) bandwidth and coupling efficiency. To\nillustrate possible improvements, we replaced the APD with a photodiode (PD), which\nincreased the receiver bandwidth and enabled 1.28 Gbps transmission with a clearer\neye diagram (Supplementary Fig. 14). This demonstrates that further optimization of\nthe hardware architecture can effectively enhance performance and points to promising\ndirections for future advancement. The following change has been made to the\nmanuscript discussion.\nChange 4:\nMain text, page 9, lines 252-258.\n“In our current setup, the achievable data rate and bandwidth are primarily\nconstrained by hardware factors such as the intrinsic bandwidth of the receiver and\ncoupling efficiency. For example, by replacing the APD with a photodiode (PD), we\nincreased the receiver bandwidth and achieved 1.28 Gbps transmission with a clearer\neye diagram (Supplementary Fig. 14). This indicates that further optimization of system\nhardware could effectively enhance performance and enable future advancements in\nthis technology.”\nSupplementary information, page 18.\n5\n“Supplementary Fig. 14. The eye diagram obtained using a photodiode receiver with\na bandwidth of 1.28 Gbps. ”\nComment 5. While the authors have demonstrated the merits of RATOF, including its\nability to establish an internet connection (Supplementary Video 2) and perform signal\nswitching (Supplementary Video 5), the quality of these videos could be improved to\nbetter convey RATOF's functionalities. Considering the importance of these videos in\ndemonstrating the system, both their content and execution should be refined to provide\nreaders with a clearer understanding and a more engaging viewing experience.\nAuthor response:\nWe thank the reviewer for the helpful suggestion regarding the supplementary\nvideos. We agree that the clarity and execution of the videos are critical for effectively\nconveying RAOF’s functionalities. (see also reviewer #3 Comment 10)\n1. In response, we have removed the original Supplementary Video S2 and replaced\nit with a new one, which demonstrates connectivity in a lab environment.\n2. Video S5 has been edited to improve visual clarity and highlight signal switching\nevents, ensuring that the demonstration of RAOF’s operational features is more\nimmediately understandable.\nWith these adjustments, we aim to provide readers with a clearer, more engaging,\nand informative viewing experience, emphasizing both the system’s functionalities and\nits potential applications.\nChange 5: The Previous Supplementary Video S2 was replaced.\nChange 6: Supplementary Video S5 has been revised by adding more textual\nannotations to highlight key signal switching events and improve viewer\ncomprehension.\nComment 6. The concept of RATOF could inspire people from various fields.\nTherefore, it is suggested that the authors provide detailed setup photos to assist\nresearchers from diverse disciplines who are interested in this work. This will enable\nthe efficient replication of experiments and further exploration of RATOF's broader\n6\napplications.\nAuthor response:\nWe thank the reviewer for the suggestion.\nThe real-time communication system is based on a conventional wide area\nnetwork (WAN) configuration, as shown in the logic diagram (Supplementary Fig. 15).\nNoted that the avalanche photodiode (APD) was initially used to ensure the efficient\ncapture of the output signal so that the signal can be restored at the output end. The real-\nworld equipment setup was shown in Supplementary Fig. 15. To offer a detailed\ninstruction on the device setup, we have added all details as follows:\nChange 7:\nSupplementary information, page 19.\n“Supplementary Fig. 15. a, Simplified schematic illustration of the set-up logic for the\nrealtime communication system, in which the RAOF is used as information transmission\nmedium. b, Digital photo of the set-up for the realtime communication system.”\nComment 7.The interfacial tension test only holds ~700s for 1.1wt% PSS, 4wt% N-\nPDMS” in stead of ~1200s as others, why?\nAuthor response:\nWe thank the reviewer for their comments, which offer an interesting point to\ndiscuss. We used the pendant drop method to measure the IFT, which is based on the\nYoung-Laplace theory, which is reliable for a liquid-like interface.2 However, when\nnanoparticles assemble to and jam the liquid-liquid interface, especially for the case\n7\nwhen the surface coverage is extremely high and the interfacial tension is remarkably\nreduced, the balance between the interfacial tension and gravity will be broken, i.e., the\nLaplace pressure is not able to hold the pendant drop, resulting in the brake up at the\nneck of pendant drop, consequently, the IFT measurement cannot hang on for 1200s as\nothers do. We have added relevant discussion to the manuscript.\nChange 8:\nMain text, page 6, lines 159-161.\n“With increasing ligand content, the interfacial tension decreases to a level insufficient\nto counteract gravity, causing pendant drop break-up, preventing long-term\nmeasurement.”\n8\n----------------------------------------------------------------------\nReport of Reviewer #2\n----------------------------------------------------------------------\nOverall Comments:\nThe manuscript reported the fabrication of a novel reconfigurable all-liquid topological\noptical fiber (RATOF) using structured liquid formation. By using 2 immiscible liquids,\nwhere the core aqueous phase had a higher, tunable refractive index, total internal\nreflection can be achieved. The high interfacial tension of the 2 liquids favored\nformation of individual droplets rather than a tubule structure. Therefore, the authors\napplied 2 polyelectrolyte and the self-assembly of them at the interface successfully\nreduced the interfacial tension to around 1 mN m, which allowed tubule formation in\nthe printing process. The formation of RATOF was well-characterized and various\ninteresting aspects regarding their RATOF were also demonstrated with adequate\nexperiments and setups. Although, based on the current experimental data about the\nproperties of the RATOF, the production and application of it might not be feasible in\nthe near future, this manuscript has successfully demonstrated new insights in future\noptical fiber designs. Nevertheless, some of the experimental data are clear enough and\nthey should be replaced by better ones and other revisions are suggested. The following\nare comments and suggestions for the authors.\nAuthor response:\nWe thank the reviewer for their valuable insights and support regarding the RAOF\nprototype we have demonstrated. As RAOF is still at a preliminary stage, the reviewer’s\nsuggestions have been instrumental in improving our demonstration and highlighting\nits potential for future optical fiber designs.\nComment 1. Page2, line 60: why soft optical fibers are primarily used as sensors rather\nthan for telecommunication? The authors might consider elaborate more so that readers\nthat are not very familiar with optical fiber can understand more about the weakness of\nsoft optical fibers in practical application, where RATOF might also experience similar\nproblems.\nAuthor response:\nWe thank the reviewer for raising this important point. Liquid core–polymer shell\nfibers, in which only the fiber core is replaced with liquid while the surrounding\nframework remains solid, have been widely applied in sensing. Their strong sensitivity\nto environmental parameters such as refractive index, temperature, pressure, and\nchemical composition makes them particularly effective for sensing applications.3,4\nHowever, this hybrid design is less suitable for telecommunication. The\nconventional liquid core-polymer shell fibers do not deviate far from the conventional\nall-glass fiber. Its solid cladding, for relatively fixed-shape constraint, means that such\nfibers still suffer from the intrinsic drawbacks of conventional solid fibers, i.e., a\n9\ndifficulty in repairing breakage. In addition, they typically exhibit higher optical loss\ncompared to silica fibers, which further limits their use in long-distance or high-\nperformance communication. The inherent similarity between these two technologies\nhas severely refrained the conventional soft fibers to be useful only to special cases like\nsensing, while general telecommunication scenarios would turn to glass fibers.\nIn contrast, all-liquid fibers—typically realized as freestanding liquid columns—\nrepresent a fundamentally different concept. These systems face severe challenges due\nto Rayleigh–Plateau instabilities, making it difficult to maintain stable guidance over\nlong durations. As a result, previous studies often relied on flow focusing or other\ncomplex strategies to stabilize the liquid column, which further constrains their\npractical utility.5,6\nOur RAOF system addresses this challenge by demonstrating that a fully liquid\nfiber can be realized without the need for flow focusing. The measured optical\nattenuation of RAOF is 0.631 dB cm-1 (see also Comment 6), which, although higher\nthan that of silica optical fibers, is on the same order of magnitude as reported values\nfor liquid core–polymer shell fibers or hydrogel optical fibers.3,7 Crucially, RAOF\nprovides additional advantages with its liquid nature: it is reconfigurable, repairable,\nand capable of overcoming some intrinsic limitations of solid fibers. Although further\nimprovements in loss are still required, our results offer new insights into the design of\nnext-generation optical fibers and highlight a promising direction beyond conventional\nsolid or hybrid structures. Additional information based on this comment was added to\nthe manuscript to offer readers more background.\nChange 9:\nMain text, page 2, lines 58-66.\n“Furthermore, many of these fibers are primarily used as sensors rather than for\ntelecommunication, mainly because their structures are designed to maximize\nsensitivity to environmental parameters (e.g., RI, temperature, or chemical\ncomposition), which is beneficial for sensing but not required for long-distance signal\ntransmission. The inherent similarity between these liquid-core–polymer-shell fibers\nand conventional all-glass fibers means that they still inherit the intrinsic limitations of\nsolid fibers, such as fixed geometry, difficulty in repairing breakage, and relatively high\noptical loss, which further restrict their use in large-scale telecommunication.”\nComment 2. From the video demonstrations, the RATOF should be immersed in a bath\nof silicone oil. Therefore, the illustration in figure 1a is a bit misleading.\nAuthor response:\nWe sincerely thank the reviewer for their rigorous suggestions. Indeed, while we\nfocused on the visual aesthetics of the figure, we overlooked the objective content and\nscientific accuracy it conveys. To prevent any potential misunderstanding, we have\nrevised the schematic in Figure 1a to ensure its rigor and scientific validity.\nChange 10:\nA revised schematic illustration of the RAOF was used in Fig.1a.\nComment 3. At the curvature shown in figure 1e, did most of the light leak?\nAuthor response:\nWe thank the reviewer for this point. As a quantitative reference, we evaluate\nbending-induced loss in RAOFs. We tested a curved fiber with a bending angle of ~34.8°\n(radius: 30.67 mm; curvature: 0.0326 mm⁻¹), which corresponds to the configuration\nused in our demonstrations of real-time communication (Supplementary Fig. 17). For a\ntypical water phase composition with [glucose] = 77.78 wt.%, under an input power of\n30 mW, the output power dropped to ~0.334 mW (including coupling loss and\ntransmission attenuation). Noted that, at the first curvature, the main reason for the light\nloss is the coupling point between all liquid optical fiber and the hardware of the system,\nwhich requires further efforts in the engineering aspect.\nFor comparison, the curvature shown in Fig. 1e is 0.111 mm⁻¹, which is larger than\nin our reference demonstration. Therefore, visually, the light leakage is expected to be\neven more pronounced. The attenuation at the curvature in both cases primarily\noriginates from scattering at interfacial imperfections, which becomes more severe as\nthe curvature increases.\nTo mitigate this effect, we tuned the glucose concentration in the aqueous phase\n11\n(see also Comment 2 from Reviewer #1). Lowering the glucose content reduces water-\nphase viscosity, promoting interfacial relaxation and eliminating wrinkles, which\nsuppresses scattering. At an optimized concentration of [glucose] =60 wt.%, the output\npower increased to ~1.7 mW, nearly five times higher than at [glucose] =77.78 wt.% as\nshown in Supplementary Fig. 10 below.\nIn summary, while bending loss remains a limitation, these results demonstrate\nthat optimizing interfacial morphology can substantially improve light transmission in\ncurved RAOFs. Our current prototype already exhibits the essential functionalities for\noptical communication, and further optimization will be important for advancing\npractical applications of all-liquid fibers. We have revised our claim in the manuscript.\nSupplementary Fig. 10. The change of detected light intensity at the output end of\nRAOF when decreasing the content of glucose in the water phase. The dashed line is a\nfitted curve to guide the eye. Values in the figure represent the mean, and the error bars\nrepresent the SD of the three measured values of each sample (n = 3). The power of all\nreplicate samples was measured by an identical power meter.\nChange 11:\nMain text, page 4, lines 123-126.\n“Upon coupling red light into the RAOF, light propagation along the inner interface\nwas observed, with obvious leakage at the bends and coupling point (Fig. 1e), likely\ndue to interfacial scattering at curved regions and the interface mismatch.”\nComment 4. The authors should include the IFT data for 3% PSS with 3% NPDMS as\nit is the condition for the RATOF printing.\nAuthor response:\nWe thank the reviewer for pointing this out. The interfacial tension (IFT) for the\ncondition of 3% PSS with 3% NPDMS, which corresponds to the RAOF printing, has\nnow been measured as ~2.7 mN m⁻¹, as shown in Fig. 2a, and is included in the revised\nmanuscript.\nChange 12:\nMain text, page 7, lines 183-185.\n12\n“Fig. 2a. Interfacial tension (IFT) evolution versus the mass concentration of PSS in\nthe water phase and N-PDMS in the oil phase.”\nComment 5.At such low IFT, it seems that the Laplace pressure is very low and not\nenough to maintain a circular cross section of the RATOF. Will the RATOF collapse\neasily under stress from the outer phase?\nAuthor response:\nWe thank the reviewer for this important comment. While a low interfacial tension\nindeed reduces the Laplace pressure and could, in principle, compromise the circular\ncross-section of the RAOF, our experiments consistently show that the fiber remains\nstable under the tested conditions. To quantitatively evaluate the factors governing the\nstability of the printed liquid tubule, we considered not only the effect of interfacial\ntension (σ ) but also interfacial elasticity (σ ), capillary pressure (σ ), and the\nγ E C\ngravitational stress. These combined contributions (σ + σ + σ ) act against gravity to\nE γ C\npreserve the structural integrity of the fiber,8-10 as also discussed in Comment 4 from\nReviewer #3.\nWe introduced total interfacial restoring stress (σ ), which balances the\nres\ngravitational stress:\nσ =σ +σ +σ\nres E γ C\nkγ\nAccording to Laplace theory，σ + σ and k=1 for tubular droplets; in this\nγ C=\nR\nγ\nway，σ =E+\nres\nR\nwhere E is the interfacial elastic modulus, γ is the interfacial tension, R is the\nradius of the liquid tubule.\nTo estimate the influence of weight difference on the shape deformation of a liquid\ntubule, the critical droplet radius R , at which interfacial restoring stress balances\nc\ngravity, is calculated as follows:\nγ\nΔρgR= E+\nR\nwhere Δρ is the density difference between the aqueous phase and the oil phase;\ng is gravitational acceleration (9.8 m/s²).\nAs a result,\nR = \nc\n2Δρg\nFor a typical demonstration in our work, i.e., [PSS]= 3 wt.% and [N-PDMS]= 3\nwt.%, the viscosity of oil phase is 60,000 cSt, Δρ=0.252 g mL-1; the interfacial tension\nis measured as ~2.7 mN m-1 (Fig. R1 a-b) and the corresponding E, measured by the\npendant drop method,2 is ~0.56 mN m-1;. As a result, R\nc\nis calculated to be ~1.05 mm:\n• For a liquid tubule with R1.05 mm, interfacial forces dominate, maintaining\nthe tubular droplet shape.\n• For droplets with R1.05 mm, the weight difference (gravity) dominates, and\nthe droplet may deform.\nFig. R1. a, Interfacial tension (IFT) evolution versus the mass concentration of\nPSS in the water phase and N-PDMS in the oil phase. b, Interfacial elasticity measured\nby the pendant-drop oscillation method. A surface area variation of 0.2% at 0.1 Hz was\napplied. These parameters were selected to simulate a quasi-static regime, in which\ninterfacial deformation is primarily governed by gravitational force. The red dashed\nline serves as a visual guide. c-d, The printed linear shape liquid tubule in silicone oil\nwith a viscosity of 1000 cSt (c) and 60,000 cSt (d), respectively.\nWhen nanoparticles self-assemble at the interface, particularly under conditions of\nvery low interfacial tension and high surface coverage, they can form nanoparticle\nsurfactants and undergo a jamming that leads to interfacial solidification. In this state,\nthe interface no longer behaves as a purely liquid boundary, and the Young-Laplace\nequation, as applied in the pendant-drop method, is not strictly valid. Consequently, the\n14\nmeasured values can only be regarded as quantitative estimates of interfacial elasticity\nand related properties, while the actual stability of the liquid–liquid interface may also\nbe governed by additional factors. For instance, the viscosity of the continuous phase\n(oil phase) plays an important role in droplet stability.10,11 A higher viscosity retards\ngravity-induced droplet deformation. This allows liquid tubules with a radius near or\nslightly above R to maintain their shape, effectively extending the stability range\nc\nbeyond the static limit defined by interfacial stress alone. To offer instruction on the\ndesign of different systems, we here make a demonstration by increasing the viscosity\nof silicone oil from 1000 cSt to 60,000 cSt. As shown in Fig. R1 c-d, when the viscosity\nof the continuous silicone oil was increased from 1000 cSt to 60,000 cSt (with all other\nparameters unchanged), the liquid tubule changed from sedimenting and bending at low\nviscosity to remaining straight and stable at high viscosity. This confirms that the\nenhanced viscous damping in the higher-viscosity medium effectively suppresses\ngravitationally induced deformation.\nIn summary, our analysis reveals that the balance between interfacial elasticity,\ninterfacial tension, capillary forces, and gravity, along with viscous damping from the\ncontinuous phase, governs droplet shape and stability. The reduced Laplace pressure\ncan be compensated by viscous stabilization of the oil phase. We have made a\ncorresponding discussion in the main text and supplementary information, also as a\nresponse to the Comment 4 from reviewer #3.\nChange 13:\nMain text, page 6, lines 175-182.\n“The stability of RAOFs arises from the combined effects of interfacial elasticity,\ntension, capillarity, and viscous damping of the continuous phase. Even with a density\ndifference between the core and oil, fibers smaller than a critical radius maintain a\ncircular cross-section. High continuous-phase viscosity and nanoparticle-stabilized\ninterfaces further enhance stability, enabling both two- and three-dimensional fiber\ndesigns. Quantitative estimates of these factors provide guidance for designing robust\nliquid fibers under gravity.”\nSupplementary information, pages 8-9.\n“The stability of printed RAOFs is determined by the interplay between interfacial\nforces (tension, elasticity, and capillary pressure) and gravitational stress due to the\ndensity difference between the core and continuous phases. Even at low interfacial\ntension, fibers maintain their circular cross-section because the combined restoring\nstress (σ ) from interfacial elasticity, interfacial tension, and capillarity can counteract\nres\nthe weight of the liquid core:\nγ\nσ =E+\nres\nR\nwhere E is the interfacial elastic modulus, γ is the interfacial tension, and R is the\nfiber radius. A critical radius R can be estimated, above which gravitational\nc\ndeformation dominates:\nR = \nc\n2Δρg\nHere, Δρ is the density difference between the aqueous core and the oil phase, and\ng is the gravitational acceleration (9.8 m/s²). For typical experimental conditions\n([PSS]=3 wt.%, [N-PDMS]=3 wt.%, oil viscosity = 60,000 cSt, Δρ = 0.252 g mL⁻¹, γ ~\n2.7 mN m⁻¹), E is ~ 0.56 mN m⁻¹, as measured by the pendant-drop oscillation method\n(Supplementary Fig. 6a). R is calculated to be ~1.05 mm. Fibers with radii smaller\nc\nthan R are dominated by interfacial forces and remain circular, whereas larger fibers\nc\nmay deform under gravity.\nIn addition, the continuous-phase viscosity plays a crucial role in stabilizing fibers:\na high-viscosity medium retards gravity-induced deformation, enabling fibers with\nradii near or slightly above R to maintain their shape (Supplementary Figs. 6b-c).\nc\nNanoparticle adsorption at the interface can further jam and solidify the boundary,\nenhancing mechanical stability. These factors together enable both two-dimensional\nand, under suitable conditions, three-dimensional fiber designs.\nSupplementary Fig. 6. a, Interfacial elasticity measured by the pendant-drop\noscillation method. A surface area variation of 0.2% at 0.1 Hz was applied. These\nparameters were selected to simulate a quasi-static regime, in which interfacial\ndeformation is primarily governed by gravitational force. The red dashed line serves\nas a visual guide. b-c, The printed linear shape liquid tubule in silicone oil with a\nviscosity of 1000 cSt (b) and 60,000 cSt (c), respectively.”\nComment 6. Could the authors provide the characterization of the signal quality based\non the length of the RATOF?\nWe thank the reviewer for this important question. The attenuation of the printed\nRAOF was determined by a standard cut-back measurement: we recorded the\ntransmitted optical power P at several tubule lengths and performed a linear regression\nof 10log P versus position L.12 The data can be described by\n10\n10log P(L)=-L+C\n10\nso that the fitted slope  directly gives the loss in dB per unit length, and the attenuation\nis ~0.631 dB cm-1.( Supplementary Fig. 11 a)\nTo characterize signal quality along the fiber, we recorded eye diagrams at\nmultiple positions corresponding to different lengths. Consistent with the cut-back\nresults, the eye-opening decreases from 0.038703 V at point 1 to 0.024333 V at point 2\n(~37% reduction), as shown in Supplementary Fig. 11 b-c, primarily due to reduced\nreceived optical power and lower signal-to-noise ratio caused by propagation loss and\ninterfacial scattering. Other metrics, such as timing jitter and eye width, remain largely\nunchanged, indicating that timing integrity is preserved while amplitude-based metrics\ndegrade with length. The reduction in eye-opening reflects the lower electrical signal\namplitude at the receiver as the optical power diminishes along the fiber. We have\nadded the corresponding discussion in the manuscript.\nChange 14:\nSupplementary information, page 15\n“Supplementary Fig. 11. a. Attenuation curve of RAOF as a function of length. The\nresults were significant within the 95% confidence interval. b-c, Eye diagrams\nmeasured at different positions along the same liquid optical fiber, corresponding to the\nred-circled point (b) and the blue-circled point (c) in (a).\nThe attenuation of the printed RAOF was determined by a standard cut-back\nmeasurement: we recorded the transmitted optical power P at several tubule lengths\nand performed a linear regression of 10log P versus position L.12 The data can be\n10\ndescribed by\n10log P(L)=-L+C\n10\nso that the fitted slope  directly gives the loss in dB per unit length.”\n“The attenuation of the printed RAOF was determined using the cut-back method,\nyielding ~0.631 dB cm-1(Supplementary Fig. 11a). To provide a qualitative analysis of\nthe signal and offer visual information on digital transmission, which serves as a first-\norder approximation of signal-to-noise ratio, clock timing jitter, and skew, the system's\neye diagram was tested (Supplementary Note 3). Eye diagrams measured at multiple\npositions along the same fiber show a reduction in eye-opening from 0.0387 V to 0.0243\nV (Supplementary Fig. 11b-c), consistent with the decrease in received optical power\nand signal-to-noise ratio with increasing fiber length, while other metrics such as\ntiming jitter and eye width remain nearly unchanged. Although the loss is higher than\nin conventional silica fibers, it is comparable to recently reported polymer-based fibers.\nImportantly, RAOFs can be printed in situ, repaired, and dynamically reconfigured,\nenabling versatile local interconnects. These results demonstrate that Gbps-level data\ntransmission is achievable over short distances, confirming the practical potential of\nRAOFs for adaptive and reconfigurable optical communication networks.”\nComment 7. For the RATOF repairing experiment, the video did not show how it was\nbroken and how it was repaired clearly. The authors should take the video at a better\nangle to clearly show the breaking and more importantly, the repairing of RATOF.\nAuthor response:\nWe thank the reviewer for this helpful suggestion. In the revised submission, we\nhave re-recorded the video from a microscopic perspective to clearly capture both the\nbreaking and repairing processes of the RAOF. This updated video provides a more\ndetailed and intuitive demonstration to help readers better understand the repairability\nof the liquid fiber.\nChange 15:\nSupplementary information\nThe original supplementary video 4 was replaced with a new version.\nMain text, pages 12-13, lines 331-349.\n18\n“Fig. 4. The demonstration of RAOF with the uniqueness of self-healing,\nreconfiguration, and flowable core. a-f, The correspondence between the state of the\nRAOF and the synchronization status of the real-time online video meeting during the\nbroken and repair process of the RAOF. a, the RAOF before being broken; b, the source\nsignal and the signal at the receiver before the RAOF broken; c, the RAOF was cut at\nthe middle point; d, the source signal and the signal at the receiver after the fiber was\nbroken, showing the offline internet connection; e, the RAOF was reparied; f, the source\nsignal and the signal at the receiver after fiber was repaired, showing that the link was\nresotred. g, Schematic illustration of the shape reconfiguration by all-liquid 3D printing.\nh, The picture of an RAOF. i, The picture of an RAOF with an additional channel\nderived from (h), forming a “Y-branched” structure with two channels, namely CH 1\nand CH 2. j, The signals from the light source, CH 1, and CH 2. k, Schematic illustration\nof the signal switch by remotely controlled ferrofluid droplet movement inside the RAOF.\nl-m, A RAOF with a ferrofluid droplet as switch for the signal switching: l, The\nferrofluid droplet is in CH 2, leading to a signal on in CH 1 while a signal off in CH 2;\n19\nm, The ferrofluid droplet is relocated in CH 1, leading to a signal off in CH 1 while a\nsignal on in CH 2. n, The signal profiles at CH 1 and CH 2 associating with l and m.\nScale bars: a-c, 1 mm; h, i, l, m, 1 mm.”\nComment 8. For figure 4J and 4K, it is better to include a video showing the movement\nof the ferrofluid droplet. It is quite interesting that the ferrofluid droplet did not break\nthe RATOF when it moved in and out of it.\nAuthor response:\nWe thank the reviewer for this constructive suggestion. In the revised manuscript,\nwe have included a supplementary video that demonstrates the movement of the\nferrofluid droplet within the RAOF, confirming that the fiber maintains its structural\nand optical integrity during this process. Regarding the implantation of the ferrofluid\ndroplet, to minimize potential damage to the liquid fiber, we introduced the droplet from\neither the input or output end of the fiber. This approach ensures minimal disruption to\nthe fiber structure and minimizes the influence on the signal transmission. We have\nadded the video to the revised submission as follows.\nChange 16:\nMain text, page 14, line 393.\nSupplementary information, page 28, lines 280-281.\n“Supplementary Video 6. The movement of the ferrofluid droplet inside the RAOF,\nwhich is controlled by an external magnetic field.”\n20\n----------------------------------------------------------------------\nReport of Reviewer #3\n----------------------------------------------------------------------\nThe authors of this paper present the realization of liquid optical fibers formed by\nstabilizing a water oil-interface by means of in-situ assembly. The method for interface\nstabilization has been pioneered by the Russel group in previous studies, but this\nmanuscript reports an impressive practical demonstration of a potential application in\ntelecommunication. The authors clearly show that their optical fibers can work as low-\nloss, broadband connectors between conventional optical fibers and allow for standard\nconnectivity supporting video feed and data transfer. The authors also show that their\noptical fibers, because made exclusively from liquid components, can be easily repaired\nand reconfigured.\nI found the demonstration very impressive, but I would ask the authors to provide\nadditional details to the manuscript to provide the quantification of essential aspects\nthat can be used as guidelines by others, as well as to provide a deeper understanding\nof the materials used.\nAfter addressing these issues, I would be happy to recommend publication.\nAuthor response:\nWe sincerely thank the reviewer for the positive and encouraging comments. All\ncomments have been addressed point-by-point, and corresponding revisions have been\nincorporated into the revised manuscript.\nMain comments:\nComment 1. How does the RI change in the presence of surfactants in the two phases?\nThe authors only report the variation of RI as function of glucose concentration in the\nSI.\nAuthor response:\nWe thank the reviewer for this valuable comment. In our system, nanoparticle\nsurfactants, formed via interfacial self-assembly between ligands from the water and\noil phases, are mainly used to stabilize the immiscible liquid-liquid interface with the\nexpectation not to significantly modify the refractive index (RI) of each phase. The\nconcentrations of ligands applied in both the core (water) and cladding (oil) phases are\ntypically below 5 wt%, which is far lower than the concentrations of glucose used to\ntune the RI. According to our additional measurements (Supplementary Fig. 2b), the RI\nvariation induced by surfactants is negligible (<0.005) compared to the RI modulation\nachieved by glucose (up to 0.15).\nMoreover, we conducted control experiments to evaluate the influence of oil-phase\nviscosity on the RI. The results demonstrate that the viscosity of the cladding oil has\nnearly no impact on the RI value. Therefore, the RI contrast in our RAOF is\npredominantly determined by the glucose concentration, while the contributions from\nsurfactants and oil viscosity are marginal. For clarity, we have added a discussion to the\n21\nrevised manuscript and included the supporting data in the Supplementary information.\nChange 17:\nMain text, pages 3-4, lines 104-116.\n“To evaluate whether the addition of ligands and the viscosity of the cladding oil\ninfluence the optical properties of RAOF, we systematically measured the RI of both\nphases under typical conditions. As shown in Supplementary Fig. 2b, the RI of the\naqueous phase containing PSS and the oil phase containing N-PDMS remain nearly\nunchanged across the ligand concentration range used in this work (<5 wt.%). The\nmaximum RI variation induced by ligands is less than 0.005, which is negligible\ncompared to the RI modulation achieved by glucose (up to 0.15). In addition, control\nexperiments were conducted with oils of different viscosities, and the results indicate\nthat viscosity has almost no effect on the RI of the cladding phase or on the effective RI\ncontrast of the RAOF. These results confirm that the RID in RAOF is predominantly\ngoverned by glucose concentration, while surfactants and oil viscosity contribute only\nmarginally to the optical guiding properties.”\nSupplementary information, page 3, lines 38-43.\n“Supplementary Fig. 2b. The refractive index of both water and oil phases as a\nfunction of ligand content.”\nComment 2. How does the presence of adsorbed NPs change the scattering of light at\nthe interface? How does the roughness of the interface reported in Figure 2d compare\nto the one of quartz fibers? What is the requirement for the roughness of the\ninterface to obtain a low loss compatible with applications?\nAuthor response:\nWe thank the reviewer for this valuable discussion. As shown in Fig. 2d, the\nnanoparticle surfactants (NPSs), formed by the interaction between ligands from both\nliquid phases, assemble and jam at the oil–water interface. Such jamming and\nthermodynamic fluctuations deform the local interface and increase interfacial\nroughness, thereby enhancing light scattering. This effect is analogous to dust\n22\nadsorption on the surface of a quartz optical fiber (Supplementary Fig. 8), which also\ninduces scattering and attenuation.\nBy analyzing the AFM image (Fig. 2d), the mean roughness (S ) of our oil–water\na\ninterface is 17.20 nm, whereas commercial optical fibers typically exhibit much lower\nsurface roughness. This difference indicates that the oil–water interface scatters light\nmore strongly, consistent with the observed attenuation in our system. 13,14\nMinimizing interfacial roughness is therefore crucial; in general, smoother\ninterfaces lead to lower optical loss. As we discuss in the manuscript, one practical\napproach is to reduce the viscosity of the oil phase, which allows local relaxation and\nsmoothing of the interface (e.g., using a 1000 cSt oil phase). Additionally, previous\nstudies have demonstrated that densely packed plasmonic nanoparticles or smaller\nparticles, i.e., gold nanoparticles, can enhance optical reflectance. 15,16\nIn summary, reducing interfacial roughness through interfacial engineering\nrepresents a key strategy for lowering loss and improving the practical applicability of\nall-liquid optical fibers. We have added a discussion to the revised manuscript.\nChange 18:\nMain text, pages 7-8, lines 203-207.\n“The adsorption and jamming of nanoparticles increase interfacial roughness (S ~ 17\na\nnm), which enhances light scattering and optical loss compared to smooth quartz fibers;\ntherefore, interfacial engineering to reduce roughness is essential for achieving low-\nloss all-liquid optical fibers.”\nComment 3. What is the density difference between the two liquids and how does that\naffect the geometry of the fibers that can be printed? I presume that the glucose-water\nmixtures are significantly heavier than the oil. Does this mean that only two-\ndimensional fiber designs resting on the bottom of a container can be realized? Is there\nan option to go in the third dimension?\nAuthor response:\nWe thank the reviewer for this important question. The density difference between\nthe glucose–water solution and the oil phase is Δρ = 0.252 g mL⁻¹. This density\nmismatch generates a gravity force that can act on the liquid interface, potentially\novercoming interfacial elasticity and tension, which may lead to shape deformations\nand interface instability during fiber printing.\nTo investigate the influence factor on the interfacial stability, we increased the\nviscosity of the oil phase. As shown in Fig. R2 a-b, we find that when the viscosity of\nthe oil phase is increased from 1000 cSt to 60,000 cSt, the printed liquid fibers can\nmaintain “floating” in the oil phase, and no obvious shape deformation is observed.\nWith the increased stability, the printed patterns are no longer confined to a two-\ndimensional plane at the container bottom but can extend three-dimension (Fig. R2 c).\nIn this condition, a higher viscosity retards gravity-induced droplet deformation,\nallowing liquid tubules with radii near or slightly above the critical radius R to maintain\nc\n23\ntheir cylindrical shape (see also Comment 4). This effectively extends the stability\nrange beyond the static limit defined by interfacial stress alone.\nEven in cases where the density mismatch causes fibers to sediment to the\ncontainer bottom, three-dimensional networks can still be constructed. Interfacial\njamming prevents adjacent tubes or channels from merging, allowing multiple layers\nto stack. This enables the formation of three-dimensional fiber architectures despite\ngravitational settling.\nIn short, by tuning the outer-phase viscosity, three-dimensional liquid fiber\ngeometries can be realized, overcoming the limitations imposed by the density\nmismatch. The change has been made in Change 13 in response to Comment 5 from\nReviewer #2. Please refer to the Main text, page 6, lines 175-182, and Supplementary\ninformation, pages 8-9.\nFig. R2. a-b, The printed linear shape liquid tubule in silicone oil with a viscosity of\n1000 cSt (c) and 60,000 cSt (d), respectively. c. A three-dimensional spring-shape\nliquid pattern in 60,000 cSt oil.\nComment 4. Along the same lines, how does the interfacial elasticity compare to\nweight difference? Providing quantitative estimates of these factors would be\ninformative to guide the design of different systems.\nAuthor response:\nWe thank the reviewer for this insightful comment. To quantitatively estimate the\ninfluence of gravitational stress on the deformation of the liquid tubule, we consider\ninterfacial elasticity (σ ), interfacial tension (σ ) and capillary pressure (σ ).8-10 These\nE γ C\neffects can be collectively described as the total interfacial restoring stress, which\nbalances the gravitational stress:\nσ =σ +σ +σ\nres E γ C\nkγ\nAccording to Laplace theory，σ + σ and k=1 for tubular droplets; in this way，\nγ C=\nR\nγ\nσ =E+\nres\nR\nwhere E is the interfacial elastic modulus, γ is the interfacial tension, R is the\nradius of the liquid tubule.\nTo estimate the influence of weight difference on the shape deformation of a liquid\ntubule, the critical droplet radius R , at which interfacial restoring stress balances\nc\ngravity, is calculated as follows:\nγ\nΔρgR= E+\nR\nwhere Δρ is the density difference between the aqueous phase and the oil phase;\ng is gravitational acceleration (9.8 m/s²).\nAs a result,\nR = \nc\n2Δρg\nFor a typical demonstration in our work, i.e., [PSS]= 3 wt.% and [N-PDMS]= 3\nwt.%, the viscosity of oil phase is 60,000 cSt, Δρ=0.252 g mL-1; the interfacial tension\nis measured as ~2.7 mN m-1 (Fig. R1 a-b) and the corresponding E, measured by the\npendant drop method,2 is ~0.56 mN m-1;. As a result, R\nc\nis calculated to be ~1.05 mm:\n• For a liquid tubule with R1.05 mm, interfacial forces dominate, maintaining\nthe tubular droplet shape.\n• For droplets with R1.05 mm, the weight difference (gravity) dominates, and\nthe droplet may deform.\nFig. R1. a, Interfacial tension (IFT) evolution versus the mass concentration of PSS in\nthe water phase and N-PDMS in the oil phase. b, Interfacial elasticity measured by the\npendant-drop oscillation method. A surface area variation of 0.2% at 0.1 Hz was applied.\nThese parameters were selected to simulate a quasi-static regime, in which interfacial\ndeformation is primarily governed by gravitational force. The red dashed line serves\nas a visual guide. c-d, The printed linear shape liquid tubule in silicone oil with a viscosity\n25\nof 1000 cSt (c) and 60,000 cSt (d), respectively.\nWhen nanoparticles self-assemble at the interface, particularly under conditions of\nvery low interfacial tension and high surface coverage, they can form nanoparticle\nsurfactants and undergo a jamming that leads to interfacial solidification. In this state,\nthe interface no longer behaves as a purely liquid boundary, and the Young-Laplace\nequation, as applied in the pendant-drop method, is not strictly valid. Consequently, the\nmeasured values can only be regarded as quantitative estimates of interfacial elasticity\nand related properties, while the actual stability of the liquid–liquid interface may also\nbe governed by additional factors. For instance, the viscosity of the continuous phase\n(oil phase) plays an important role in droplet stability.10,11 A higher viscosity retards\ngravity-induced droplet deformation. This allows liquid tubules with a radius near or\nslightly above R to maintain their shape, effectively extending the stability range\nc\nbeyond the static limit defined by interfacial stress alone. To offer instruction on the\ndesign of different systems, we here make a demonstration by increasing the viscosity\nof silicone oil from 1000 cSt to 60,000 cSt. As shown in Fig. R1 c-d, when the viscosity\nof the continuous silicone oil was increased from 1000 cSt to 60,000 cSt (with all other\nparameters unchanged), the liquid tubule changed from sedimenting and bending at low\nviscosity to remaining straight and stable at high viscosity. This confirms that the\nenhanced viscous damping in the higher-viscosity medium effectively suppresses\ngravitationally induced deformation.\nIn summary, our analysis reveals that the balance between interfacial elasticity,\ninterfacial tension, capillary forces, and gravity, along with viscous damping from the\ncontinuous phase, governs droplet shape and stability, providing a guideline for\ndesigning various droplet systems. The change has been made in Change 13 in response\nto Comment 5 from Reviewer #2. Please refer to the Main text, page 6, lines 175-182,\nand Supplementary information, pages 8-9.\nComment 5. What is the smallest and largest fiber diameter that can be printed? What\nare the limiting factors?\nAuthor response:\nWe thank the reviewer for this insightful comment. As discussed in Supplementary\nNote 1, the achievable fiber diameter is influenced by several factors, including nozzle\ngeometry, liquid viscosity, interfacial tension, and the suppression of Plateau–Rayleigh\ninstability. Specifically, during water–oil printing, the liquid thread tends to break up\ninto droplets due to Plateau–Rayleigh instability. This can be temporarily suppressed\nby increasing the viscosity of both phases and by moving the printing head at sufficient\nspeed to generate viscous stresses. These effects can be quantified by the capillary\nnumber (Ca = \nη\ne\nve),\nwhere η is the viscosity of the external liquid, v is the printing\ne e\nγ\now\nspeed, and γ is the interfacial tension. A threshold of Ca ≥ 5 is generally required to\now\novercome interfacial tension and maintain tubular geometry.\nIn addition to suppressing P-R instability, the stability of the printed fibers is\ngoverned by interfacial jamming arising from interfacial assembly. Nanoparticle\n26\nsurfactant assembling at the liquid–liquid interface creates a jammed layer that\nmechanically stabilizes the interface and the shape of the fiber, preventing breakup and\nallowing the tubular geometry to persist even under conditions that would otherwise\nfavor droplet formation. To make this clearer in the main text, we have revised the\nrelevant paragraph as follows:\nChange 19:\nMain text, page 6, lines 167-175.\n“To further benefit the fabrication of RAOFs and make them adaptable to practical\napplications, the parameter domain of all-liquid 3D printing for RAOFs was studied.\nBy varying the concentration of interfacially active components, printing speed, nozzle\ndiameter, and liquid flow rates, diameters of RAOFs ranging from ~300 µm to 1.7 mm\nwere successfully fabricated (Supplementary Fig. 5, Supplementary Note 1). The\naccessible range is mainly limited by nozzle geometry, liquid viscosity, and interfacial\ntension, as well as the tendency of fibers to break up due to Plateau–Rayleigh instability;\nthis is mitigated by interfacial jamming induced by interfacial assembly, which\nmechanically stabilizes the fibers and preserves their tubular geometry.”\nSupplementary information, page 6, lines 79-84.\n“In addition to suppressing P-R instability, the stability of the printed fibers is\ngoverned by interfacial jamming arising from interfacial assembly. Nanoparticle\nsurfactant assembling at the liquid–liquid interface creates a jammed layer that\nmechanically stabilizes the interface and the shape of the fiber, preventing breakup and\nallowing the tubular geometry to persist even under conditions that would otherwise\nfavor droplet formation.”\nComment 6. What is the loss per unit length? Based on these numbers, how do the\nliquid fibers compare to glass ones? Is there any real potential for communication or\nshould the liquid fibers be considered only useful for local connections which can be\nrepaired and reconfigured?\nAuthor response:\nWe thank the reviewer for this important question. The attenuation of the printed\nRAOF was determined by a standard cut-back measurement: we recorded the\ntransmitted optical power P at several tubule lengths and performed a linear regression\nof 10log P versus position L.12 The data can be described by\n10\n10log P(L)=-L+C\n10\nso that the fitted slope  directly gives the loss in dB per unit length.\nThe slope of this regression gives the attenuation of ~0.631 dB cm-1, which is\nindeed higher than that of conventional silica fibers but comparable to recently reported\npolymer-based fibers (e.g., hydrogel optical fibers (1.07 dB cm-1),7 glycerol/PMMA\n27\ncore-shell structured optical fiber (17.2 ± 2.4 dB m-1)3 ). However, unlike solid fibers,\nRAOFs can be directly printed, repaired, and dynamically reconfigured in situ, which\noffers unique advantages for local interconnects and reconfigurable optical networks.\nWhile long-distance communication is currently limited by interface scattering and\ncoupling losses, our experiments already demonstrate that Gbps-level data transmission\nis fully achievable, highlighting the practical potential of RAOFs in short-range,\nadaptive photonic applications. Looking forward, as the design and fabrication\nprocesses are further optimized, RAOFs may overcome current short-range limitations\nand potentially find applications in practical optical communication systems. The\nchange was made in Change 14 in response to Comment 6 from Reviewer #2. Please\nrefer to the Main text, pages 8-9, lines 227-241, and Supplementary information, pages\n15.\nMinor/general comments:\nComment 7. I do not understand the meaning of the choice of the term “topological”\nin the naming of the fibers. If anything, these can be called “topologically\nreconfigurable” but I think that “reconfigurable” suffices. I would not know what a\ntopological fiber is.\nAuthor response:\nWe thank the reviewer for this insightful comment. In the original manuscript,\n“topological” was intended to emphasize the structural reconfigurability of RAOFs—\ntheir ability to change optical topology even after the fiber is fabricated—rather than to\nrefer to topological states in the physical or mathematical sense (e.g., a topological\ninsulator). We agree that this term may cause confusion and have revised the wording\nthroughout to “reconfigurable liquid optical fibers,” which more accurately conveys the\nsystem’s versatile programmability and in situ adaptability.\nChange 20:\nMain text\nInappropriate use of the term “topological” has been removed from the main text, and\nthe associated concept has been carefully redefined to emphasize the structural\nreconfigurability of the fibers without ambiguity.\nComment 8. The authors should also elaborate further on the notion of underwater\ncommunication and how their technology applies to it, given that the optical fiber is\nimmersed in an oil bath.\nAuthor response:\nWe thank the reviewer for this important comment. Our long-term goal is to\nadvance the use of RAOFs for underwater optical communication. In the current stage,\nwe employ an oil-based external phase because such immiscible systems are\nexperimentally well-established and provide a stable and controllable environment to\ninvestigate interfacial self-assembly and optical waveguide function. Moreover, the\n28\nrefractive index and viscosity of the glucose–water mixtures used as the inner phase\ncan be precisely tuned, which is necessary for systematically studying the optical and\ninterfacial properties of RAOFs. In principle, by reversing the phase configuration,\nthat is, using water as the external phase and a high-refractive-index oil as the inner phase,\nsimilar liquid fibers could support underwater optical communication. Realizing such\nsystems, however, will require further engineering optimization, which represents an\nimportant direction toward our long-term goal. We have made corresponding\nclarifications in the revised manuscript.\nChange 21:\nMain text, Page 3, lines 79-85;\n“While our long-term aim is to develop liquid fibers for underwater optical\ncommunication, we employ an oil-based external phase in the present study because\nsuch immiscible systems are experimentally well-established and allow precise control\nof interfacial and optical parameters. The RI and viscosity of the glucose–water inner\nphase can be conveniently tuned, providing a reliable platform to investigate interfacial\nself-assembly and waveguiding mechanisms.”\nMain text, Page 15, lines 418-421.\n“This innovation offers valuable insights for future implementations in underwater\noptical communication, where appropriate refractive index contrast and immiscible\naqueous systems could be employed.”\nComment 9. There are many typos along the text and figure captions. There are also\nsome sweeping statements such as “The concept of 3D reconfigurable optical\nwaveguide design is groundbreaking” (line 326) or “This opens up tremendous new\nresearch opportunities” (line 346), which I leave to the editor’s judgement.\nAuthor response:\nWe sincerely thank the reviewer for pointing this out. We have carefully proofread\nthe manuscript and corrected typos in both the main text and figure captions.\nIn addition, in the operation of traditional quartz optical fibers and photonic\nintegrated circuits, signal switching and on–off control necessitate the integration of an\nadditional switch, which imposes significant challenges in terms of logical design and\nsystem implementation. Moreover, it is difficult to reconfigure the optical fibers once\nfixed to a device setup. In these conditions, real-time reconfiguration of quartz optical\nfibers to adapt to dynamic application environments requires additional complicated\ntechniques. In contrast, the RAOF has the flexibility to enable a real-time and easy\nreconfiguration by 3D printing, offers a new paradigm to optical waveguide design, and\nopens new opportunities for further investigations in related fields. In this consideration,\nwe have rephrased some descriptions and discussions to ensure scientific objectivity.\nRegarding the mentioned overstated claims.\nTypos:\nManuscript, page 1, line 34; page 2, lines 35-36, 40, 42, 46, and 57; page 4, lines 117\nand 131; page 5, lines 137, 144, 146; page 7, lines 189-190; page 10, lines 271, 273,\n277; page 11, lines 302 and 306; page 13, line 367 and 369; page 14, lines 376, 380,\n396 and 400; page 17, line 506.\nRephrased descriptions:\nMain text, page 14, line 384.\n“The concept of 3D reconfigurable optical waveguide design offers a new paradigm.”\nMain text, page 14, line 404.\n“This opens new opportunities for further investigation.”\nComment 10. I found the supplementary video S2 not very useful and not quite\nappropriate, given that it shows the arbitrary browsing and shows personal information\nsuch as browsing history etc. The videos showing the connectivity in a lab environment\nare, in my opinion, much more appropriate and effective. The video with the online\nmeeting is also only mildly relevant. I would in general think that the authors should\ncarefully consider the relevance, content and format of the video (image and sound).\nAuthor response:\nWe thank the reviewer for the valuable comments regarding the supplementary videos.\n1. We agree that the original video was not sufficiently informative and included\nunnecessary content. We have removed the original Supplementary Video S2 and\nreplaced it with a new one, which demonstrates connectivity in a lab environment.\nWe have made a revision in Change 5 in response to the Comment 5 from reviewer\n#1.\n2. Regarding the online video meeting, our intention was to illustrate that RAOF can\nfully perform the functions of conventional optical fibers, even in real-time\ncommunication scenarios. We believe this practical, life-oriented demonstration is\nhelpful for conveying the potential applications of RAOF. To better reflect this\npurpose, we have revised and adjusted the video so that readers can more clearly\nunderstand its relevance to our study.\nChange 23: We have revised and adjusted the Supplementary Video 3 by adding the\nillustration of the role of RAOF in the real-time communications system. In addition,\nFig. 3f was revised to enhance the clarity of the data presentation and its scientific\nprofessionalism.\nAdditional changes:\nChange 24:\nSupplementary information, page 3, lines 43-45:\n“Values in a and b represent the mean, and the error bars represent the SD of the three\nmeasured values of each sample (n = 3). The RI of all replicate samples was measured\n30\nby an identical RI meter.”\nChange 25:\nThe contribution from Dr. Xinke Tang was missed in the original version, and we\ncorrected this in the revised manuscript.\nMain text, page 21, line 645.\n“S.Z. Y.W., S. C., X. T., and X. G. conducted the telecommunication experiments.”\nChange 26:\nIn the revised Supplementary Video 4, we included brief excerpts from the official\nvideo of City University of Hong Kong to illustrate the laboratory environment.\nPermission for academic use was obtained from the City University of Hong Kong, and\nan acknowledgement has been added accordingly.\nMain text, page 21, lines 625-626:\n“We thank City University of Hong Kong for allowing the use of excerpts from its\nofficial promotional video in the supplementary materials.”\nChange 27:\nWe revised the statement about Data availability and Code availability according to\n“Data availability statements and data citations policy.”\nMain text, page 18, lines 533-537:\n“Source data for figures are provided with this paper.”\n“The code used for the 3D printing and analysis of the telecommunication is freely\navailable through Zenodo at https://doi.org/10.5281/zenodo.17493408.”\nReferences\nEducation, 2009).\nfrom dynamic pendant-drop characterizations. Nature Protocols 20, 363-386\n(2025). https://doi.org/10.1038/s41596-024-01049-0\nLiquid-core polymer optical fibers for luminescent waveguide applications.\nMaterials & Design 196, 109131 (2020).\nhttps://doi.org/https://doi.org/10.1016/j.matdes.2020.109131\nmicrostructured polymer optical fiber. Opt. Express 14, 4135-4140 (2006).\nhttps://doi.org/10.1364/OE.14.004135\n31\nMultistable Core Actuated by Light Radiation Pressure. Physical Review Letters\n101, 014501 (2008). https://doi.org/10.1103/PhysRevLett.101.014501\nsustained by light radiation pressure: Electromagnetic model and geometrical\nanalog. Physical Review A 78, 013835 (2008).\nhttps://doi.org/10.1103/PhysRevA.78.013835\noptogenetics during locomotion. Nature Methods 20, 1802-1809 (2023).\nhttps://doi.org/10.1038/s41592-023-02020-9\nstability and shape change of anisotropic endoskeleton droplets. Soft Matter 10,\n7647-7652 (2014). https://doi.org/10.1039/C4SM01482K\nSurfactants at the Oil–Water Interface. Langmuir 35, 13340-13350 (2019).\nhttps://doi.org/10.1021/acs.langmuir.9b01575\n1707603 (2018). https://doi.org/https://doi.org/10.1002/adma.201707603\nDevices by 3D Printing. Small 20, 2405892 (2024).\nhttps://doi.org/https://doi.org/10.1002/smll.202405892\nShort Range Transmission Systems. Second Edition. edn, (Springer-Verlag,\n2008).\nsensitivity of fiber-optic evanescent wave sensors. Appl. Opt. 52, 3937-3945\n(2013). https://doi.org/10.1364/AO.52.003937\nscattering loss of small-core polymer waveguides for single-mode optical\ninterconnect applications. Opt. Express 28, 38733-38744 (2020).\nhttps://doi.org/10.1364/OE.410283\nInterfaces. ACS Nano 7, 9241-9248 (2013). https://doi.org/10.1021/nn403879g\nMaterials 16, 1127-1135 (2017). https://doi.org/10.1038/nmat4969\n32"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The author have revised the manuscript based on the reviwer's suggestion. I would recommend the publication of this manuscript on Nature communications.", "reviewer_2": "The authors have addressed all my concerns/suggestions and the manuscript has been revised accordingly. It can be published as it.", "reviewer_3": "I would like to thank the authors for considering all of my comments and also the ones raised by the other reviewers. The revised manuscript and the response letter clearly address all issues raised during the first revision round. As a result, the revised manuscript is considerably improved and makes a stronger case about the potential of the proposed technology.\nI am therefore happy to recommend publication"}, "author_response": "Response Letter\nWe thank both reviewers for their kind and positive comments. The following is a\npoint-by-point response to both reviewers’ comments.\n----------------------------------------------------------------------\nReport of Reviewer #1\n----------------------------------------------------------------------\nThe author have revised the manuscript based on the reviwer's suggestion. I would\nrecommend the publication of this manuscript on Nature communications.\nAuthor's reply: We thank the reviewer for their scientific discussion of our work and\nthe positive comments.\n----------------------------------------------------------------------\nReport of Reviewer #2\n----------------------------------------------------------------------\nThe authors have addressed all my concerns/suggestions and the manuscript has been\nrevised accordingly. It can be published as it.\nAuthor's reply: We thank the reviewer for their scientific discussion of our work and\nthe positive comments.\n----------------------------------------------------------------------\nReport of Reviewer #3\n----------------------------------------------------------------------\nI would like to thank the authors for considering all of my comments and also the ones\nraised by the other reviewers. The revised manuscript and the response letter clearly\naddress all issues raised during the first revision round. As a result, the revised\nmanuscript is considerably improved and makes a stronger case about the potential of\nthe proposed technology.\nI am therefore happy to recommend publication.\nAuthor's reply: We thank the reviewer for their scientific discussion of our work and\nthe positive comments.\n1"}]

Decision letter