Review Reports - Profiled Wet Spinning of Polyurethane Composites for Soft Dry Electrodes in Transcutaneous Stimulation Applications

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors The manuscript presents a well-structured and methodologically sound study devoted to the development of soft dry electrodes for transcutaneous stimulation, specifically for taVNS. The authors propose two approaches to electrode creation: classic wet spinning of fibers and profiled wet spinning to produce hollow cylindrical structures. Comments: 1. Line 140 states, "The conductive polymer composite used in this study consists of polyurethane (PU) and carbon black (CB)." A description of the polyurethanes used is necessary, as the study is based on the properties of polyurethanes. 2. For this reason, the characteristics of carbon black (CB), including the manufacturer's specifications, should also be provided. 3. Table 1 states, "Resistance measured…." It should be clarified that this is specific volume electrical resistance. Or is this referring to a different type of resistance? 4. Why was the 6% CB composition chosen for further experiments? Was an analysis of the mechanical properties (tensile strength, elongation at break) and stability performed? Why wasn't a formulation with, for example, 7% CB considered? 5. Was the possibility of using other conductive fillers (e.g., graphene, carbon nanotubes) in the same profile spinning process considered to further reduce the filler content and improve the mechanical properties? 6. In Figures 8b and 8c, it is unclear whether the "wet" and "dry" data refer to the same components. Please clarify this point in the caption. 7. How is the decrease in resistance in the first few cycles explained? Is this due to a restructuring of the conductive network or to material compaction?

Author Response

The manuscript presents a well-structured and methodologically sound study devoted to the development of soft dry electrodes for transcutaneous stimulation, specifically for taVNS. The authors propose two approaches to electrode creation: classic wet spinning of fibers and profiled wet spinning to produce hollow cylindrical structures.

A: We are thankful for your consideration of our work and helpful comments on the manuscript. We have revised the manuscript according to your comments. You will find the answers to your comments below.

Comment 1: 1. Line 140 states, "The conductive polymer composite used in this study consists of polyurethane (PU) and carbon black (CB)." A description of the polyurethanes used is necessary, as the study is based on the properties of polyurethanes.

A: Thank you, indeed, this crucial information was regrettably omitted in the initial version of the manuscript. We now include a new section ‘2.1. Materials’, where we describe the source and properties of the materials used. We mention the brand of the commercial Elastollan 1170A polyurethane and how we dried it before usage.

Comment 2: 2. For this reason, the characteristics of carbon black (CB), including the manufacturer's specifications, should also be provided.

A: New section 2.1. also describes the types and sources of the carbon black and solvent used. We now report porosity and bulk density of the specific batch of CB used, as provided by the supplier.

Comment3: 3. Table 1 states, "Resistance measured…." It should be clarified that this is specific volume electrical resistance. Or is this referring to a different type of resistance?

A: Thank you, it was indeed not clear. In fact, we have measured electrical resistance along the length of the produced fibers, and the Table reports average data measured for several fibers produced at a given filler content. We have now added a paragraph describing the measurement exactly to be more clear. The table header was also updated to say “Lengthwise Fiber electrical resistance of the fibers” to remove any confusion. We have also used this opportunity to extend the measurements with more data points, and now include more precise data.

Comment4: 4. Why was the 6% CB composition chosen for further experiments? Was an analysis of the mechanical properties (tensile strength, elongation at break) and stability performed? Why wasn't a formulation with, for example, 7% CB considered?

A: Thank you for this comment. The elongation was not tested robustly enough in the first draft of the manuscript. We have now carried out tensile testing of the produced fibers and report both elongations at break and elastic moduli for all the studied ranges of filler content.

Indeed, 7% filler content could have been an optimal content. Initially we skipped this number only because of the coarseness of the optimization step (2%). We have now investigated fibers produced 7% filler content too.

6% CB composite remains the leader composite in terms of resistance/elasticity. In the revised manuscript, we now discuss this choice and observed characteristics in the text more.

Comment5: 5. Was the possibility of using other conductive fillers (e.g., graphene, carbon nanotubes) in the same profile spinning process considered to further reduce the filler content and improve the mechanical properties?

A: This is indeed an intriguing opportunity. Your assessment is correct, as usage of nanotubes for example can lead to similarly conducting material, which would be more elastic and soft. We briefly mention that state-of-the-art research involves composites using nano carbons and metallic nanoparticles. While we will pursue usage of nano-fillers in our future research, we chose carbon black in this work due to its availability and known safety to skin.

We have now extended the Introduction part of the manuscript to also provide this argumentation:

“Meanwhile, carbon black remains cheaper than the nanotubes/nanoparticles in terms of achieving similar electrical performance of composites and devices [28,29] and is known to be safe to use with human skin [30], which is relevant for TENS applications. Compared to nanotubes and nanoparticles, higher concentration of carbon black is needed to achieve similar electrical performance, which also leads to much stiffer composite materials.”

Comment6: 6. In Figures 8b and 8c, it is unclear whether the "wet" and "dry" data refer to the same components. Please clarify this point in the caption.

A: The figure caption has been extended to include a description of what ‘wet’ and ‘dry’ means in this context.

“Wet” refers to measurements performed after applying an electrolyte spray to the electrode surface, whereas “dry” refers to measurements taken without electrolyte. Wet and dry data were obtained from the same electrode types, consisting of Ag plate, Ag + fiber, and profiled elastic electrodes, as indicated in the legend (wet vs. dry shown for each material).”

Comment7: 7. How is the decrease in resistance in the first few cycles explained? Is this due to a restructuring of the conductive network or to material compaction?

A: Precisely. This is a well-known effect in piezoresistive conductive elastomeric composites. As you mention, the applied strain leads to elastic deformation of the elastomer matrix, which, in its turn leads to the structural changes in the conductive filler percolation networks. Not always does such effect lead to ‘good’ changes, i.e. lower resistance, but the majority of conductive composites stabilize after some pre-treatment. In elastic composites this is usually repeated pre-strain or pre-compression.

In the revised manuscript we have expanded the explanation of the observed resistance change over cycles.

Reviewer 2 Report

Comments and Suggestions for Authors

In this work, the authors provide a method called ‘profiled wet spinning’ through wetting spinning of conductive elastomer into fibers, which makes electrodes conform to complex geometry. The paper provides electromechanical testing, including tensile and compression, to demonstrate the material durability and piezoresistive behavior. The extension of wet spinning to create complex 3D geometry is innovative and addresses a real clinical need for taVNS applications.

In general, the paper presents solid work. The innovation and contents are sufficient. The reviewer would recommend publishing this paper. While there are some room to improve the paper:

The conductive polymer composite lacks a biocompatibility test and a long-term stability test.
It is okay to test on the arm for a materials-focused paper, but authors need to clearly state limitations regarding anatomical testing and biocompatibility. There is no strong support that the proposed technique could resolve the challenge of the complexity of 3D ear geometry.
The huge shrinkage during the fabrication process may lead to a big challenge in real applications. It may not be a focus in this work, but if authors have ways to reduce the shrinkage, the material can be more promising.

Comments on the Quality of English Language

There are many typos and grammar issues. For examples, in line 16, grammatical issue ‘Transcutaneous auricular vagus nerve 15 stimulation (taVNS), in which nerve stimulation is delivered through the skin of the 16 external ear. ‘ in line 40. Typo issue ‘taVNS is an active are of research for its possible application in neurorehabilitation’. Line 65, delete ‘in’ ‘Most intensive research in in the context of innovative adaptable conductive 66 electrode materials is carried out in the domain of conductive elastomer composites [18]. ‘ Please check and revise the paper carefully before publishing

Author Response

Reviewer 2. In this work, the authors provide a method called ‘profiled wet spinning’ through wetting spinning of conductive elastomer into fibers, which makes electrodes conform to complex geometry. The paper provides electromechanical testing, including tensile and compression, to demonstrate the material durability and piezoresistive behavior. The extension of wet spinning to create complex 3D geometry is innovative and addresses a real clinical need for taVNS applications.

In general, the paper presents solid work. The innovation and contents are sufficient. The reviewer would recommend publishing this paper. While there are some room to improve the paper:

A: Thank you for your assessment of our work. We have now significantly improved the manuscript thanks to your comments. You will find our response to your comments below.

Comment 1. The conductive polymer composite lacks a biocompatibility test and a long-term stability test.

A: While we do aim for the transcutaneous applications, the main focus of the present work is on the development of the profiled spinning technique. The biocompatibility studies together with further taVNS performance assessments and performance in ear will be the topic of our further research.

While Elastollan 1170 used in the present work was not tested for cytotoxicity, medical grade analogs (e.g. Tecothane, ChronoFlex) of the same precursor material with similar mechanical and chemical properties are readily available. We will further investigate if these materials can be used in the profiled spinning process.

As for long-term stability, we have now carried out elasticity and resistance measurements for the composites stored for 30 days in darkness. The data show that both conductivity and elasticity are preserved while in storage. It is known that PU is susceptible to degradation under UV and humidity exposure. Our use-case, however, does not require prolonged exposures to neither of these factors, as taVNS electrodes are meant to be disposable, one day use items.

We now expanded the manuscript with the appropriate data and statements:

“It is known that PU can degrade over time, especially under UV and humidity exposure [43]. In the perspective use case, however, the taVNS electrodes would not be exposed to any of these factors for prolonged amount of time, as the envisioned electrodes are meant to be disposable. Degradation of PU in storage, however, is still important. Electromechanical tests and resistance measurements after storage of a fiber in a polyethylene bag and in darkness for 30 days show that the operational parameters (elasticity and electrical resistance) of the fiber do not change significantly.”

Comment 2. It is okay to test on the arm for a materials-focused paper, but authors need to clearly state limitations regarding anatomical testing and biocompatibility. There is no strong support that the proposed technique could resolve the challenge of the complexity of 3D ear geometry.

A: Thank you very much for this helpful remark. The goal of the present work was to establish a basis for future in‑ear testing, and we do agree that this intent and its limitations were not communicated clearly enough in the original manuscript. The main motivation of the current measurements was to compare standard silver electrodes with the developed profile‑spun elastomeric electrodes in such a way to abstract the anatomical complexity of the ear.

To enable a standardized comparison, we therefore mounted the tested materials on the arm with a constant electrode spacing. This experimental setup provided controlled spacing and reduced inter‑participant variability, allowing us to focus on the material‑ and geometry‑related electrical/impedance performance of the compliant electrodes. As you rightly point out, such tests cannot demonstrate that the new material solves the challenge posed by the complex three‑dimensional geometry of the ear or its specific tissue composition.

We also agree that, at present, rigid metal electrodes are poorly compatible with the auricular anatomy, and our work should be seen as a step toward addressing this limitation rather than a complete solution. A systematic investigation of CBPUC electrodes in the ear, including anatomical fit and biocompatibility, will be the focus of future studies.

Meanwhile, in the revised manuscript, we now expand on the argumentation of using arm as the stimulation site in the material tests, and also add the following disclaimer about our findings in methods:

“Electrodes were mounted with a constant spacing of 6 cm and pressed against the skin using a weighted fixture (380 g per electrode) to replicate tight-fitting electrode-ear conditions. The arm was used in our preliminary stimulation studies as a flatter anatomical site, allowing consistent electrode spacing and inter-participant variability.”

And in the results sections:

“It’s important to also note that the arm was not intended to replicate the geometry, curvature or tissue composition of the auricle and the results may not fully predict the performance and biocompatibility with the complex three-dimensional structure of the ear, and this remains to be further investigated.”

Comment 3. The huge shrinkage during the fabrication process may lead to a big challenge in real applications. It may not be a focus in this work, but if authors have ways to reduce the shrinkage, the material can be more promising.

A: Indeed, shrinkage can pose a significant problem in the implementation of this method. On another hand, other parameters exist that can affect the shrinkage – composition of the coagulation bath, stirring, extrusion speed, usage of other solvents in the spinning dope, etc. While the aim of the present work is to establish the proof-of-concept, all these factors can be studied further to eliminate this issue.

If carefully studied, shrinkage can be disregarded in the production, for example by predicting its extent. For example, knowing that the composite shrinks by 30%, the nozzle diameter/features can be increased by 30% to compensate. Quite likely, this behaviour is not linear, but as you have mentioned, this lies outside the scope of the present work.

We now somewhat expanded discussion of the shrinkage in the revised manuscript:

“For example, knowing that the composite shrinks by 30 %, the nozzle diameter or size of other features can be increased appropriately to compensate. Other parameter, such as coagulation bath and spinning dope compositions, stirring, exposure time, etc, can drastically affect the shrinkage of the produced shape as well. Study of these effects, however, is outside of the scope of the present proof-of-concept study.”

Comment 4: There are many typos and grammar issues. For examples, in line 16, grammatical issue ‘Transcutaneous auricular vagus nerve 15 stimulation (taVNS), in which nerve stimulation is delivered through the skin of the 16 external ear. ‘ in line 40. Typo issue ‘taVNS is an active are of research for its possible application in neurorehabilitation’. Line 65, delete ‘in’ ‘Most intensive research in in the context of innovative adaptable conductive 66 electrode materials is carried out in the domain of conductive elastomer composites [18]. ‘ Please check and revise the paper carefully before publishing

A: Thank you very much for pointing this out. We have used this opportunity to correct the errors and typos, as well as to improve the text quality overall in the revised manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript deals with wet spinning of a polyurethane (PU) composite with carbon black (CB) to obtain conductive elastomer and fiber with hollow cylindrical fibers. Its application aims at transcutaneous auricular vascular nerve stimulation (taVNS). This is a well-written paper, and it is recommended to accept it for publication after some revision on the basis of comments below.

COMMENTS

In general, the targeted application belongs to the so called “Transcutaneous Electrical Nerve Stimulation (TENS)” processes, and this has to be mentioned by the authors in their manuscript. A broader readership is more familiar with TENS than taVNS.

The source, purity and purification methods of the applied compounds are not described by the authors. All these should be provided in a separate “Materials” subsection (as subsection 2.1) in the 2. Materials and Methods section. Otherwise, interested scientists and engineers will not be able to reproduce the processes and obtained composites. Other details, for instance the composition of the so called “coagulation bath”, the time required for coagulation and precipitation and drying in air etc., are not given in this manuscript. Taking into account that reproducibility is the most important aspect of a scientific/technical publication, detailed experimental description is required by the authors in this manuscript.

The authors use dimethylformamide (DMF) as solvent to prepare the fibers of the PU-CB composite fibers. However, DMF is a toxic substance. Therefore, its complete removal from the formed fiber is critical if someone would like to use the compoite fiber in taVNS application. The authors have to provide detailed analysis on the DMF content of the fibers formed by coagulation and precipitation after “air drying” at room temperature, noting that DMF has low vapor pressure and high boiling point.

The authors mention the physical state of the produced fibers with various CB contents, but solid data on the mechanical properties, such as modulus and elongation at break etc., are not provided at all. The authors have to present such data for all the fiber samples.

It is absolutely unclear which sample’s data are displayed in Figure 3. This should be added in the caption of this Figure.

As shown in Table 1, the resistance of the fibers changes dramatically, nearly two orders of magnitude, for the fibers between 4% and 6% CB. Did the authors carry out direct structural analysis of these fibers to obtain direct structural evidence which can offer explanation for this observation?

The size of the electrodes in Figures 7a, 7b and 7c should be provided for comparison.

On page 14, the authors claim that “the materials used in the process are cheap and skin safe”. Did the authors perform skin tests, which support this claim?

Author Response

A: We are grateful for your assessment of our work. We have followed your comments and suggestions and have now significantly improved the manuscript in this revision. You will find answers to your comments below.

COMMENTS

Comment 1. In general, the targeted application belongs to the so called “Transcutaneous Electrical Nerve Stimulation (TENS)” processes, and this has to be mentioned by the authors in their manuscript. A broader readership is more familiar with TENS than taVNS.

A: Thank you, indeed. We have now revised the Introduction and abstract sections of the manuscript to start with TENS and mention that taVNS is a type of TENS in general.

Comment 2. 2. The source, purity and purification methods of the applied compounds are not described by the authors. All these should be provided in a separate “Materials” subsection (as subsection 2.1) in the 2. Materials and Methods section. Otherwise, interested scientists and engineers will not be able to reproduce the processes and obtained composites. Other details, for instance the composition of the so called “coagulation bath”, the time required for coagulation and precipitation and drying in air etc., are not given in this manuscript. Taking into account that reproducibility is the most important aspect of a scientific/technical publication, detailed experimental description is required by the authors in this manuscript.

A: Thank you very much for your comment. Indeed, this important information was somehow omitted from the initial version of the manuscript. We have now made a section 2.1 Methods, where the sources of the materials and their properties are listed.

While the composition of the bath and the important production parameters were mentioned in the production section, they were indeed not clearly marked. We have now revised the appropriate sections to be very clear what are the production parameters.

Comment 3. 3. The authors use dimethylformamide (DMF) as solvent to prepare the fibers of the PU-CB composite fibers. However, DMF is a toxic substance. Therefore, its complete removal from the formed fiber is critical if someone would like to use the compoite fiber in taVNS application. The authors have to provide detailed analysis on the DMF content of the fibers formed by coagulation and precipitation after “air drying” at room temperature, noting that DMF has low vapor pressure and high boiling point.

A: Thank you for a very important comment. Indeed, DMF is a toxic compound, and probably the only component of the studied material with documented harmful properties in regards to skin exposure. This, as you also mention, is further complicated by the fact that DMF can be retained by the material and is very hard to evaporate.

We had initial indications that DMF is leaving the composite after spending 3h in water due to appearance of consistent mechanical behaviour, but this indeed merits a more robust test.

We have now performed more analyses in this regard, namely we employed FTIR spectroscopy to analyse how much DMF is retained by the samples that spent different amount of time in the coagulation bath. The data show that even the thick CBPUC electrode samples are devoid of DMF after 60 minutes of solvent exchange. We however, as was previously stated, used 3h duration for the process, which produces safe material, according to the FTIR data too.

You will find a new data and text in the experimental section (2.5), and in the results and discussion (3.4) devoted to these experiments.

Comment 4. 4. The authors mention the physical state of the produced fibers with various CB contents, but solid data on the mechanical properties, such as modulus and elongation at break etc., are not provided at all. The authors have to present such data for all the fiber samples.

A: Thank you, indeed, somehow these important data have not been reported. We have now carried out additional characterization of the samples, improve the resistance measurements, and also present the data for the elastic moduli and elongations at break for all the samples. The measurements are summarized in Table 1 and are further discussed in the appropriate chapter.

Comment 5. 5. It is absolutely unclear which sample’s data are displayed in Figure 3. This should be added in the caption of this Figure.

A: Thank you for catching this. The data presented correspond to the 6%CB fiber. We have now edited the figure caption accordingly.

Comment 6. 6. As shown in Table 1, the resistance of the fibers changes dramatically, nearly two orders of magnitude, for the fibers between 4% and 6% CB. Did the authors carry out direct structural analysis of these fibers to obtain direct structural evidence which can offer explanation for this observation?

A: This is indeed a very interesting phenomenon. While it is well known in the field of conductive composites and piezoresistive materials, we have expanded the description and the reasons for that in the text to be more complete.

Briefly, this is a very typical behaviour for the composites containing conductive particles. At very low concentrations, no electrical contact between particles exists, making the overall composite barely conductive. Addition of more and more conductive filler leads to only a slight increase of conductivity until a point is reached, where whole chains and paths of the conductor are being formed within the polymer matrix. This is concentration called a percolation threshold. Increasing conductor content after this concentration leads to a progressively higher and higher conductivities orders of magnitude higher. Addition of further filler usually leads to insignificant improvement of conductivity, since the conductive networks are already fully formed. In the revised manuscript, we describe this phenomenon and related changes in more details now.

Reorganization of this percolative networks upon cyclical straining is also a known effect, which explains the improvement of conductivity, observed in Fig 3a. We also describe it in more detail in the revised text.

Comment 7. 7. The size of the electrodes in Figures 7a, 7b and 7c should be provided for comparison.

A: Thank you for your note. The revised version of the figure now provides scale bars on each photograph, making it visible that the electrodes are of similar dimensions.

Comment 8. 8. On page 14, the authors claim that “the materials used in the process are cheap and skin safe”. Did the authors perform skin tests, which support this claim?

A: Thanks for this remark, indeed, we did not perform the skin tests. However, we did not observe any adverse reactions on the skin of the participants during the impedance tests. Also, in absence of DMF (as we have now shown is the case) the materials used in the work are generally considered safe for skin exposure.

However, you are absolutely right, without robust confirmation we cannot claim this. We have now removed this claim in the revised manuscript.

Reviewer 4 Report

Comments and Suggestions for Authors

The article “Profiled Wet Spinning of Polyurethane Composite of Soft Dry Electrodes for Transcutaneous Stimulation Applications” by Shokurov and coworkers presents an interesting contribution in which a novel material for soft dry electrode is introduced. The authors have presented the results systematically, and the different sections are well-connected. The article may be of interest to Materials readers, although some points require further consideration before a final decision is made. Therefore, I recommend a major revision.

The authors should answer the following:

The same definition of VNS is repeated in the first two paragraphs of the introduction.
The authors should use space between the number and units throughout the manuscript
The authors should define which of the conductances were considered good and how was this determined.
How is the resistance of the obtained materials compared to the state of the art materials that are already in use?
Why is the size of pores important for the potential use? What is the range of pores in similar materials?
The authors should compare the performances of the obtained material with similar materials in literature to support further experiments.
More of the quantitative data should be included in the conclusion.

Author Response

A: Thank you for your consideration of our work, and thank you for your comments. We have now significantly improved the study. You will find the detailed responses to your comments below.

The authors should answer the following:

Comment 1. The same definition of VNS is repeated in the first two paragraphs of the introduction.

A: Thank you for bringing it to our attention. The issue has now been rectified.

Comment 2. The authors should use space between the number and units throughout the manuscript

A: We have made sure all the units are now space separated in the revised version of the text, thanks!

Comment 3. The authors should define which of the conductances were considered good and how was this determined.

A: Indeed, it is not a very obvious definition. We have now expanded the manuscript text to discus son this. Briefly, while it is evident that higher conductivity is always better, in context of conductive composites it comes with diminishing mechanical properties. So, in our work, we now analyze both resistance and elasticity of the compounds, noting that while kOhm range is not perfect it is still less than the skin impedance, which makes it possible to use the composites in transcutaneous stimulation applications.

Comment 4. How is the resistance of the obtained materials compared to the state of the art materials that are already in use?

A: This is indeed important. While the present work is not focused on improving conductivity beyond state-of-the-art, but instead is devoted to prove the concept of profiled spinning methodology, the answer to this question remains important.

However, in the revised version of the manuscript we now include a direct comparison of resistances.

The text now mentions some prominent examples of similar materials and emphasises the focus of the present study more:

“The developed wet-spun PU fiber exhibits a resistance in the kΩ range, comparable to PU/CB composites achieving 1-100 kΩ/cm resistivity near percolation[47], and PU/CNT fibers reaching lower values of ~10-1000 Ω/cm at high loadings[48]. Notably, comparison of resistances, especially in fiber form is tricky, as several methods of reporting it can be used. Also, mechanical properties should be considered alongside the electrical ones, when considered for TENS applications. All in all, optimization of electrical resistance was not the primary goal of the present study, which focused instead on mechanical and structural properties, as well as possibility to performed profiled spinning for taVNS electrode applications”

Comment 5. Why is the size of pores important for the potential use? What is the range of pores in similar materials?

A: This is an intriguing question. To the best of our knowledge, no studies explicitly examine pore size ranges (e.g., micro- vs. macro-pores) in foamed composites for transcutaneous electrodes' performance metrics such as impedance or current distribution.

From the perspective of the current work, the size of pores is not strictly important. The fact that the material conveniently comes out porous after the wet spinning is advantageous for the application in question mainly due to the intrinsic softness/compressibility of the porous materials in general. This is reflected by measured <1 MPa Young’s moduli of the obtained samples, indicating that they are indeed soft, and much more compressible/elastic than bulk Elastollan1170 (~20MPa modulus).

Investigation of ways to induce pores of different sizes and how that would affect electromechanical performance of the composites, especially in the context of transcutaneous stimulation can be an attractive field of study.

Nevertheless, we have expanded on the role of pores in the context of trans-skin electrodes in the introduction of the paper, and also in the discussion of our own porous material.

Comment 6. The authors should compare the performances of the obtained material with similar materials in literature to support further experiments.

A: Thank you. Indeed, as we mentioned above, we compare the resistances of the similar materials found in the literature. Transcutaneous stimulation field is very rich, and some thorough analyses of the materials were done. We now compare our electrodes with the commercial and some advanced composites reported in the literature.

The manuscript has been extended with the following comparison:

“Moreover, the CBPUC-based electrodes demonstrated superior skin–electrode impedance characteristics compared with commercially available transcutaneous electrode materials. Marquez-Chin et al. reported average impedance values of 36.06 ± 77.70 kΩ for hydrogel electrodes, 401.19 ± 664.63 kΩ for dry polymer nanocomposite electrodes, and 970.51 ± 1933.12 kΩ for dry carbon rubber electrodes. In contrast, both dry CBPUC electrodes investigated in this study (dry Ag + fiber and dry profiled elastic) exhibited substantially lower impedances, consistently below 20 kΩ”

Comment 7. More of the quantitative data should be included in the conclusion.

A: Thank you. We now provide elastic moduli, resistances for the produced fibers and electrodes, along with the impedances.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have answered all the reviewer's questions. The article can be recommended for publication.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have answered all the questions appropriately, and the manuscript is suitable for publication in its present form.