Principles of Operation and Application Extensions of Triboelectric Nanogenerators: Structure and Material Optimization

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript provides a comprehensive review of recent progress in implantable bioelectronics based on energy harvesting technologies. However, there are several areas that require improvement to enhance clarity and rigor:
1. The distinction between implantable bioelectronics and wearable or semi-implantable devices should be made clearer, especially in the introduction and classification of energy harvesting types.
2. Transitions between sections (e.g., from energy harvesting mechanisms to bioelectronics applications) feel abrupt. Consider refining the logical flow and hierarchy of the sections.
3. Terms such as “fully implantable,” “semi-implantable,” and “bio-integrated” are used interchangeably in places. Clear definitions should be provided and applied consistently.
4. While many studies are cited, some are only briefly mentioned. For example, in the TENG section, deeper discussion on in-vivo performance or chronic implantation challenges would be beneficial.
5. Some figures (e.g., Figure 4、Figure 7、Figure 8) are low-resolution and difficult to interpret. Please ensure all figures are clear, labeled properly, and directly support the narrative.
6. The current conclusion is mostly descriptive. Consider summarizing key challenges (e.g., encapsulation, chronic biocompatibility) and proposing future research directions more explicitly.

Comments on the Quality of English Language

The manuscript is generally well-written and clear. However, several sentences could benefit from improved grammar, punctuation, and clarity. A careful proofreading or professional English editing is recommended to enhance readability.

Author Response

Dear Reviewer1,

I sincerely appreciate your valuable comments on my manuscript. Based on your feedback, I have made the following revisions and improvements:

Question 1:The distinction between implantable bioelectronics and wearable or semi implantable devices should be clearer, especially in the introduction and classification of energy harvesting types.

Author's Reply1: Thank you for your valuable feedback. I agree that a clearer distinction between implantable bioelectronics and wearable or semi-implantable devices is important for enhancing the understanding of energy harvesting types in the manuscript. In response, I have expanded the discussion in the introduction and the classification section to more clearly define the differences between these devices.Additionally, I have incorporated a more detailed description of wearable and implantable devices into the single-electrode section of Figure 4. This update helps illustrate how these devices operate differently in the context of energy harvesting, emphasizing their unique features, applications, and challenges.These revisions aim to provide a clearer understanding of the various device categories and their corresponding energy harvesting mechanisms. I believe this will make the classification more comprehensive and accessible to the readers.

Question 2:The transition between segments (e.g. from energy harvesting mechanisms to bioelectronic applications) feels sudden. Consider refining the logical flow and hierarchical structure of each section.

Author's Reply2:.Thank you for your constructive feedback. I appreciate your observation regarding the transition between segments, particularly between the discussion of energy harvesting mechanisms and bioelectronic applications. I agree that improving the logical flow and structure would enhance the overall readability of the manuscript.In response, I have updated and refined the content to ensure a smoother transition between sections. The connection between energy harvesting mechanisms and their applications in bioelectronics is now more clearly outlined, with additional linking statements and context to guide the reader through the progression of ideas. These adjustments aim to create a more cohesive narrative that seamlessly integrates the different aspects of the topic.

Question 3:Terms such as "fully implantable," "semi implantable," and "biointegrated" are interchangeable in some places. Clear definitions should be provided and consistently applied.

Author's Reply3:Thank you for your insightful comment. I understand that the terms "fully implantable," "semi-implantable," and "biointegrated" are used interchangeably in some sections of the manuscript, which could lead to confusion. I have carefully reviewed and revised the usage of these terms to ensure that each is clearly defined and consistently applied throughout the article.In the revised manuscript, I have provided precise definitions for each term to distinguish their specific meanings and applications. These definitions are now clearly stated in the relevant sections, ensuring that the reader can easily follow the distinctions between them.This revision should improve both the clarity and consistency of the manuscript. I appreciate your suggestion, which has helped refine the precision of the terminology and the overall coherence of the text.

Question 4:Although many studies have been cited, some are only briefly mentioned. For example, a more in-depth discussion on in vivo performance or chronic implantation challenges would be beneficial in the TENG section.

Author's Reply4:In response to your comment, I have expanded the discussion within the single-electrode section to include a more thorough analysis of implantable devices and their related challenges, particularly in terms of long-term in vivo performance and the difficulties encountered with chronic implantation. This additional content addresses key issues such as biocompatibility, device stability, and the impact of prolonged implantation on device functionality, which are crucial for the practical application of TENGs in bioelectronics.These revisions aim to provide a more comprehensive understanding of the topic and highlight important considerations for the development of TENGs in implantable bioelectronics. I believe this will contribute to a more balanced and detailed presentation of the challenges in this field.

Question 5:Some numbers (such as Figure 4, Figure 7, Figure 8) have low resolution and are difficult to explain. Please ensure that all numbers are clear, labeled correctly, and directly support the narrative.

Author's Reply5:Thank you for your helpful feedback. I acknowledge the concern regarding the resolution and clarity of Figures 4, 7, and 8, and I agree that clear, high-quality figures are essential for supporting the narrative effectively.In response, I have updated these figures to ensure higher resolution and improved clarity. Additionally, I have revised the corresponding text descriptions to better align with the content of the images, ensuring that the figures are not only visually clear but also directly support the key points discussed in the manuscript. These updates aim to enhance the overall readability and ensure that each figure is easily interpretable by the reader.

Question 6:Currently, most of the conclusions are descriptive. Consider summarizing key challenges (such as encapsulation, chronic biocompatibility) and more clearly proposing future research directions.

Author's Reply6:Thank you for your valuable feedback. I agree that the conclusions in the original version were more descriptive and could benefit from a clearer focus on key challenges and future research directions. In the revised manuscript, I have expanded the conclusion section to address critical challenges in TENG research, including encapsulation strategies, long-term biocompatibility, device stability, and large-scale manufacturing.Additionally, I have more explicitly outlined forward-looking research directions, such as the development of advanced encapsulation materials, systematic in vivo biocompatibility studies, the design of multifunctional hybrid systems, and the exploration of novel applications at the solid-liquid interface. These revisions aim to provide readers with a clearer roadmap for overcoming current limitations and pursuing promising opportunities in the field.Furthermore, the language in the conclusion has been reorganized and refined to improve clarity, and Figure 9 has been added to provide a visual summary of the key findings and an overview of future research directions.

Overall, after careful revisions, I believe the readability and professionalism of the article have been greatly improved. Thank you again for providing valuable feedback, and we look forward to your further feedback.

Best regards!

Reviewer 2 Report

Comments and Suggestions for Authors

This paper, “Working Principle and Research Development of Friction Triboelectric Nanogenerator” is a review that systematically summarizes the operating principles and research trends of triboelectric nanogenerators (TENGs). It covers the operating principles and some research on TENGs. However, the paper requires overall modifications and is not suitable for publication for the following reasons.

 

1. The overall structure of the paper is poor. The order of the figures is jumbled, and the figures presented in the text are of poor resolution, making it difficult to distinguish what they are trying to convey. Especially, Figure 7 is so poorly demonstrated that it is extremely difficult to understand the author's intention.
2. The studies presented in the paper are too old, and there are so many similar review papers that this paper lacks originality.
3. The author does not mention the full names of abbreviations such as WSA-TENG, PR-TENG, etc.

Author Response

Dear Reviewer2,

 

I sincerely appreciate your valuable comments on my manuscript. Based on your feedback, I have made the following revisions and improvements:

Question1：The overall structure of the paper is poor. The order of numbers is chaotic, and the resolution of the numbers presented in the text is poor, making it difficult to distinguish what they are trying to convey.

Author's Reply1：Thank you for your valuable feedback. We apologize for the confusion caused by the chaotic order of numbers and the poor resolution of the images in the text. In response to your comment, we have made several revisions to improve clarity:The numbering of figures and sections has been reorganized to follow a more logical and consistent order throughout the paper. This will ensure better flow and understanding for the reader.We have enhanced the resolution of all figures to improve their visibility and readability, making sure that the numbers and labels in the images are distinct and easy to interpret.Specifically, Figure 7 has been completely reconstructed to ensure it aligns more effectively with the text and conveys the intended information clearly and comprehensively.We hope these revisions address the concerns raised and improve the overall clarity and quality of the paper."

Question2：Especially, Figure 7 is presented so poorly that it is difficult to understand the author's intention. The research presented in the paper is too outdated, and there are too many similar review papers, resulting in a lack of originality in this article.

Author's Reply2："Thank you for your insightful comments. We acknowledge the concerns raised regarding Figure 7 and the originality of the paper. Please allow us to address these points in detail:Figure 7 Presentation: We understand that Figure 7 was previously unclear and did not effectively convey the intended message. In response, we have significantly revised Figure 7 to improve both its design and clarity. The figure has been reconstructed with higher resolution, clearer labeling, and a more precise alignment with the text, ensuring that the research objective and findings are better communicated to the reader.Originality of the Research: Regarding the concern about the perceived lack of originality and the presence of similar review papers, we would like to highlight that, while the field has seen extensive review work, this paper offers a unique perspective by approaching the subject from the standpoint of researchers themselves. Specifically, the paper explores the integration of structural optimization at the physical level and material updates at the chemical level, emphasizing how these strategies can drive the expansion of Teng's application field. This focus on the evolving needs and preferences of researchers is what sets our work apart from existing reviews and provides a fresh angle for further investigation in this area.We hope these clarifications address your concerns and demonstrate the value and originality of the research presented."

Question3：The author did not mention the full names of abbreviations, such as wsa teng, pr teng, etc

Author's Reply：The full name and abbreviation of the picture annotation at the bottom of Figure 7 are marked

Overall, after careful revisions, I believe the readability and professionalism of the article have been greatly improved. Thank you again for providing valuable feedback, and we look forward to your further feedback.

Best regards!

Reviewer 3 Report

Comments and Suggestions for Authors

This article provides a comprehensive and well-structured review of triboelectric nanogenerators (TENGs), covering fundamental operating principles, four representative operating modes, current applications, and materials research. I believe this TENG review has the potential to generate significant research interest among fellow researchers. However, I identify several critical issues that require major revision before publication in Micromachines. My specific concerns are outlined below:

1. Inconsistent Focus on Piezoelectric vs. Triboelectric Systems

Given that this review focuses specifically on triboelectric nanogenerators, the inclusion of piezoelectric content appears incongruous and poorly integrated. The manuscript lacks a thorough comparative analysis between triboelectric and piezoelectric mechanisms, and the inclusion of piezoelectric explanation in Figure 1(b) within the main figure seems unjustified. I recommend either: (i) expanding the piezoelectric discussion to provide a comprehensive historical comparison of piezoelectric and triboelectric technologies, including their respective advantages and limitations, or (ii) removing piezoelectric content entirely from the main figures and discussion.

2. Ambiguous Classification of Rotating Motion in Operating Modes

The classification criteria for distinguishing between sliding mode and freestanding mode require clarification, particularly regarding the categorization of rotating motion. Figure 3(f) appears to represent a freestanding mode configuration, but this classification needs explicit justification. I request the authors' perspective on this classification and suggest adding clear, distinguishing criteria for freestanding mode to eliminate ambiguity.

3. Incomplete Representation of Single Electrode Mode

Unlike other operating modes, the single electrode mode lacks a schematic illustration, making it difficult for readers to understand the operational mechanism. I recommend adding a schematic diagram for this mode. Additionally, Figure 4(c) appears to show two electrodes, which contradicts the single electrode designation. I suggest reorganizing the figure set to ensure consistency and clarity.

4. Limited Discussion of Emerging Applications

While the authors propose "application extension" as a research direction, I suggest incorporating emerging trends in triboelectric energy harvesting, particularly solid-liquid interface applications. Contact-electro-catalysis represents a significant emerging application area that warrants inclusion. I recommend the authors reference https://doi.org/10.1021/acsaelm.4c00531 and incorporate discussion of solid-liquid interface research trends to strengthen the application extension section.

5. Insufficient Author Perspective and Future Outlook

The review would benefit from increased author perspective and critical analysis throughout. Additionally, I strongly recommend including a prospective figure illustrating future research directions, which would provide valuable guidance for readers seeking to identify promising research avenues in the TENG field.

Author Response

Dear Reviewer3,

I sincerely appreciate your valuable comments on my manuscript. Based on your feedback, I have made the following revisions and improvements:

Question1： Inconsistent attention to piezoelectric and frictional systems Given that the focus of this article is on frictional nanogenerators, the inclusion of piezoelectric content seems to be inconsistent and lacks integration. The hand lacks a thorough comparative analysis between the frictional and piezoelectric mechanisms, and it seems unreasonable to include the piezoelectric explanation in Figure 1 (b) within the main figure. I suggest: (I) expanding the discussion on piezoelectricity to provide a comprehensive historical comparison of piezoelectricity and frictional electricity technologies, including their respective advantages and limitations, or (ii) completely removing piezoelectricity content from the main graphics and discussions.

Author's Reply1： Specifically, the image in Figure 1(b) has been replaced with a schematic that more directly illustrates the charge transfer process occurring when two electrode layers come into contact. This revision ensures that the figure now highlights the fundamental principle of triboelectricity, without unnecessary overlap with piezoelectric concepts.In addition, the corresponding textual description has been updated to align with the revised figure, emphasizing the mechanism of charge transfer in triboelectric systems rather than discussing piezoelectricity. These modifications improve the focus and consistency of the manuscript, ensuring that the discussion remains coherent with the central theme of frictional nanogenerators.

Question2：Fuzzy classification of rotational motion in operation mode

The classification criteria for distinguishing between sliding mode and independent mode need to be clarified, especially regarding the classification of rotational motion. Figure 3 () seems to represent an independent pattern configuration, but this classification requires clear reasons. I request the author's viewpoint on this classification and suggest adding clear criteria for distinguishing independent modes to eliminate ambiguity.

Author's Reply2： Regarding Figure 3(f), I have made the necessary modifications to provide a more detailed and accurate representation. Additionally, in Figure 5(d) of the independent layer module, I have added further explanations and visual cues to better clarify the distinction between the independent mode and the normal mode.

In the revised manuscript, I have also introduced explicit criteria for differentiating the independent mode from other modes, ensuring that the classification process is more transparent and less ambiguous. These criteria include specific characteristics of rotational motion, such as the relative movement of the components, the presence of frictional forces, and the behavior of the system under different operational conditions. These improvements aim to eliminate any confusion regarding the classification and to provide a more robust framework for understanding the rotational motion in the system.

Question3： Incomplete representation of single electrode mode

Unlike other operating modes, the single electrode mode lacks a schematic diagram, making it difficult for readers to understand the operating mechanism. I suggest adding a schematic for this pattern. Additionally, Figure 4 (c) appears to show two electrodes, which contradicts the designation of a single electrode. I suggest reorganizing the number set to ensure consistency and clarity.

Author's Reply3： In response, I have updated the manuscript by adding a clear schematic representation of the single-electrode mode. This diagram provides a more intuitive understanding of how the single-electrode mode operates and how it differentiates from other modes.Regarding Figure 4(c), I acknowledge your observation that it appears to show two electrodes, which contradicts the designation of a single electrode. I have revised the figure to ensure it accurately reflects the single-electrode configuration. Furthermore, to enhance clarity, I have reorganized the numbering and labeling in the figure to ensure consistency across the manuscript.Additionally, I have included more details about the application of the single-electrode mode in implantable and wearable devices. These additions aim to better illustrate the practical implications and working principles of the single-electrode mode in various real-world scenarios.

Question4：Limited discussion on emerging applications

Although the author proposes "application extension" as a research direction, I suggest combining it with the emerging trend of frictional energy harvesting, especially in solid-liquid interface applications. Contact electrocatalysis represents an important emerging application field worth including. I suggest the author refer to it https://doi.org/10.1021/acsaelm.4c00531 And combined with the discussion of trends in solid-liquid interface research, to strengthen the application expansion part.

Author's Reply4：After reviewing the recommended references, I summarized their contents and added Figure 3(c), which includes an image and description of the solid-liquid interface mode, along with the corresponding references. I appreciate your suggestion to incorporate the emerging trend of triboelectric energy harvesting, especially in the context of solid-liquid interfaces. I agree that contact electrochemistry is an important emerging application area and deserves inclusion.

In response to your feedback, I have thoroughly examined the suggested reference [https://doi.org/10.1021/acsaelm.4c00531] and comprehensively discussed the development trends of solid-liquid interface research. I believe this addition significantly strengthens the "Application Expansion" section.

Thank you again for your valuable feedback, which has greatly improved the manuscript.

Question5： Insufficient author perspective and future prospects

The entire review will benefit from an increase in the author's perspective and critical analysis. In addition, I strongly recommend including a forward-looking number indicating future research directions, which will provide valuable guidance for readers to seek promising research avenues in the field of Teng.

Author's Reply5：Thank you for providing constructive feedback. I fully agree that the manuscript would benefit greatly from strengthening the author's viewpoints, adding more critical analysis, and highlighting future prospects. Based on your suggestions, I have revised the discussion section to incorporate deeper critical insights and provide a more comprehensive evaluation of the current progress and limitations of triboelectric nanogenerator (TENG) research. Additionally, I have added a prospective section outlining possible future research directions, such as optimization of solid-liquid interface applications, integration with flexible wearable electronic devices, and exploration of hybrid systems based on triboelectric nanogenerators (TENG).

Overall, after careful revisions, I believe the readability and professionalism of the article have been greatly improved. Thank you again for providing valuable feedback, and we look forward to your further feedback.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have carefully addressed the reviewer’s feedback, making significant refinements to the manuscript and supporting materials. They have incorporated relevant references, provided more detailed explanations of the mechanisms, and improved the quality and informational content of the figures. These revisions have notably enhanced the manuscript’s clarity. Considering these improvements, the reviewer recommends the manuscript for acceptance in Micromachines.

Author Response

Question:The authors have carefully addressed the reviewer’s feedback, making significant refinements to the manuscript and supporting materials. They have incorporated relevant references, provided more detailed explanations of the mechanisms, and improved the quality and informational content of the figures. These revisions have notably enhanced the manuscript’s clarity. Considering these improvements, the reviewer recommends the manuscript for acceptance in Micromachines.

Author's Reply:Thank you for your thorough review and valuable feedback. We greatly appreciate your recognition of the refinements we have made to the manuscript. We have diligently addressed the suggestions and incorporated the necessary revisions, including the addition of relevant references, more detailed explanations of the mechanisms, and improvements to the figures to enhance clarity and informational content. We are pleased that these revisions have positively contributed to the quality of the manuscript. Your recommendation for acceptance in Micromachines is highly appreciated, and we look forward to the next steps in the publication process.