Simultaneous Sensing of Touch and Pressure by Using Highly Elastic e-Fabrics
Round 1
Reviewer 1 Report
This paper presents a hybrid fabric sensor. The work is interesting and useful, but the following points should be considered:
1) You mention your sensor as a 3D fabric e-skin. However, it looks like a sheet-structure, which I assume is still 2D. You may need to carefully define your ‘3D’.
2) The manufacturing process looks not ‘simple’ unless you can quantitatively compare your sensor with other existing work.
3) Is silver paste no toxic? If low toxic, any better electrode material candidate?
4) You claimed your sensor breathable. Then I assume environment may influence your sensor performance such as sensitivity and hysteresis issues. I believe a sensor should discuss these points and suggest solutions to these issues.
5) A supplementary video to Fig. 8 is needed.
Author Response
Thank you so much for your comments!
Reviewer 1:
Comments and Suggestions for Authors
This paper presents a hybrid fabric sensor. The work is interesting and useful, but the following points should be considered:
1) You mention your sensor as a 3D fabric e-skin. However, it looks like a sheet-structure, which I assume is still 2D. You may need to carefully define your ‘3D’.
=> Removed “3D”.
2) The manufacturing process looks not ‘simple’ unless you can quantitatively compare your sensor with other existing work.
=> Done in the Introduction section, yellow text:
“The manufacturing process, as shown in Figure 1, allows for rapid, reliable, and scalable production of large sensor sheets. Because this process just focuses on printing the layers, so it is more simple than other existing works [26, 44]. Otherwise, the screen printing technology is easy to approach and apply in industry. The fabrication method demonstrated the possibility of mass production for wide applications in soft robotics, health monitoring, human motion tracking, or prosthetics devices.”
3) Is silver paste no toxic? If low toxic, any better electrode material candidate?
=> Done in the Introduction section (yellow text), and Reference [33]:
“The resulting e-fabric-skin has high flexibility, breathable, lightweight, and easy integration on to clothing. The CNTs is toxic for the skin, but it will be covered by silver pastes. As knowledge of the authors, the toxic of silver is very low, and there are no materials cheaper than and least harmful to the skin as silver [33] in order to make electrode materials.”
4) You claimed your sensor breathable. Then I assume environment may influence your sensor performance such as sensitivity and hysteresis issues. I believe a sensor should discuss these points and suggest solutions to these issues.
=> Done in the Characterization of the e-fabric skin section (yellow text), Figure 7, and Figure S2 (Supporting Information).
“Figure 7a-b shows the effect of environments on the performance of the sensors. The capacitance has...”
“Besides, Figure 5e also shows the breathable ability of this structure that is impermeable to water and permeable to air. Figure S2 (Supporting Information) demonstrates the test method for determining the breathability of the sensors. The sample was kept on the hand within 5 hours. This skin area is not itchy or discolored when comparing to the beside skin area.”
5) A supplementary video to Fig. 8 is needed.
=> Added Video S1.
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
see attached document
Comments for author File: Comments.pdf
Author Response
Thank you so much for your comments!
Reviwer 2:
TITLE AND ABSTRACT
The title fits to the corresponding content. But, the touch fabrics do not assess all possible spatial directions of touches, so the title with 3D could be misleading.
=> Removed “3D”.
The introduction of this paper says that the focus lies in assessing high repeatability and hysteresis free pressure responses. Thus, the results regarding the hysteresis should also be mentioned in the abstract. In addition, the sensitivity results are of interest here.
=> Done in Abstract section (yellow text), and Characterization of the e-fabric skin section (yellow text), and Figure 7.
“Hysteresis is the maximum difference between the output values obtained...”.
INTRODUCTION
The introduction is well written. It describes the potential and applicability of e-skins in different fields as well as diverse approaches in developing them. Finally, the necessity of developing further approaches becomes clear, because limitations of the previous works is mentioned (ll. 35 f). However, the comparison of capacitive and resistive sensors should be underlined by studies comparing different measurement principles (ll. 28 f). It is also unclear whether the following sources [23-26] are only examples of previous approaches dealing with capacitance for developing an e-skin.
=> Added reference [46]
It is unclear what harm-ness in line 41 mean. Also the breathability, the benefits of the stretchable silver paste, the performance (deformation and response rate) as well as in particular the harmlessness of using the e-skin on the human skin (line 41-45) appears to be just claimed and not proven by a study. This should be adapted by the authors.
=> Done in the Introduction section (yellow text), and reference [33]
“The resulting e-fabric-skin has high flexibility, breathable, lightweight, and easy integration on to clothing. The CNTs is toxic for the skin, but it will be covered by silver pastes. As knowledge of the authors, the toxic of silver is very low, and there are no materials cheaper than and least harmful to the skin as silver [33] in order to make electrode materials.”
The reasons why this manufacturing process is suitable for mass production remains unclear (line 49).
=> Done in the Introduction section (yellow text), and reference [26], [34].
“The manufacturing process, as shown in Figure 1, allows for rapid, reliable, and scalable production of large sensor sheets. Because this process just focuses on printing the layers, so it is more simple than other existing works [26, 34]. Otherwise, the screen printing technologies are easy to approach and apply in industry. The fabrication method demonstrated the possibility of mass production for wide applications in soft robotics, health monitoring, human motion tracking, or prosthetics devices.”.
Maybe the description and figure of the manufacturing process should be shifted to chapter 2 “materials and methods” for a better readability and to give immediately more details.
=> Moved the Figure 1 to the Materials and Methods section.
MATERIALS AND METHODS
For me it is unclear, what the SWCNT ink 0,1 wt% in line 86 is. What means the percentage? Also what does the ratio 76/24 mean in line 88? Should it be specified which printing technology in line 96 they had used? Which technology, which tool, which machine? This explanation is a little too vague for me.
=> Done in the Fabrications of the sensor layers section (yellow text), and Supporting Information
“In the first step, the SWCNT ink 0.1 wt% (the weight percent...”
“In the second step, the SWCNT ink and silver pastes were applied on the PET/SP fabric (Figure 1b-c-d-e-f-g) and the PET/SP spacer fabric (Figure 1h-i-k-l-m) by screen printing technologies...”
Is the developed manufacturing process a unique invention or is it inspired/derived from previous works? Here, it appears as a unique invention, because no other sources are mentioned.
=> The developed manufacturing process of this e-fabric skin is a unique invention of authors.
RESULTS AND DISCUSSION
In this version, there is a large empty space after line 107. This should be adapted in the final version. The authors explain well the working principle of each sensor layer. However, it remains unclear what dimensions are realized for the respective prototype and what are the smallest possible dimensions/resolutions (see line 118-120, line 125-129).
=> Done in the Structure section (yellow text).
“The diamond structures have been selected for the capacitive touch layer with the pitch of 14 mm and the gap of 2 mm...”
“The column structures have been selected for the capacitive pressure layer with the width of each sensing plate (column/row) is 12 mm, and the gap between two plates is 5 mm. These dimensions/resolutions of two sensing layers were chosen in order to easily make the prototype samples. In the screen printing technologies on the fabric, the smallest size of each electrode line should be about 0.1 mm to ensure the working performance, but it needs more experiments to get the final size.”.
For me the conclusion in line 139 needs to be further explained. Why does the spacer layer help to increase the applicability in wearable research? Are there any other studies dealing with this problem?
=> Done in the The capacitive pressure sensor layer section (yellow text), and reference [26], [43], [44].
“The spacer layer, by PET yarns of the spacer fabric, will improve the elasticity of the electrodes, thereby increasing the sensitivity of the sensor in for the flexible applications in the wearable research [26, 43-44]. ”.
The abbreviation “SEM” in line 155 needs to be explained by first appearance.2 It should be explained what the abbreviation UTM (line 169) stands for. It is also of interest how the authors applied the pressure levels ranging from 0 to 100 kPa (line 170). It is difficult to understand, because first the prototype are described and up to line 167 the experiments for the electronic response are introduced. It would be better to integrate the construction etc. into the previous chapter (and to use the chapter „Protoype development“). This would make it clearer, particulary with regard to research objectives. Then, please change the 3rd chapter to „experiment“ and use the subsections „structure“, „results“ and „discussion“.
=> Done in the Characterization of the e-fabric skin section (yellow text).
“the scanning electron microscope (SEM)”
“universal testing machine (UTM machine, South Korea)”
=> Restructured of the paper (Experimetal,...)
In line 173: The given pressure sensitivity is not equal for the range, but only valid for a pressure of 100 kPa, this should be mentioned.
=> Done in the Characterization of the e-fabric skin section (yellow text).
“There are two slopes based on 60 kPa. The pressure...”.
The test method for determining the breathability should be explained in line 178. The given figure is not sufficient enough. Also the order of the pictures in fig. 5 are not matching the order of appearance/explanation in the text. This should be revised for the final version to improve the readability.
=> Done in the Characterization of the e-fabric skin section (yellow text), Figure 5, and Figure S2 (Supporting Information).
“Besides, Figure 5e also shows the breathable ability of this structure that is impermeable to water and permeable to air. Figure S2 (Supporting Information) demonstrates the test method for determining the breathability of the sensors. The sample was kept on the hand within 5 hours. This skin area is not itchy or discolored when comparing to the beside skin area.”
Please match in line 194 the sources [39- 41] to the respective application field. Line 199 says that the resistance change of the sensor under strain 20% is visualized in c), but here is a strain range from 0 to 20 % shown. The abscise should be modified to stretch like it is said in line 212.
=> Done in the Characterization of the e-fabric skin section (yellow section), and Figure 6.
“Response/recovery times and breathable ability become important...”
The last sentence in line 213 should be reviewed, because it is not understandable to me. Maybe “ In real applications, sensors often face high stretches and large deformation.”
=> Done in the Characterization of the e-fabric skin section (yellow section).
“In real applications, sensors often face high stretches and large deformation (Figure 6e).”.
The comparison of this e-skin to other works is suitable. The “better breathable properties” in line 218 should be more specified. The application example in Fig. 8 is suitable but should be extended to an example with varying pressures that are detected by the pressure sensor layer but not by the sensor layer.
=> Done in the Characterization of the e-fabric skin section (yellow section), Figure 8, and Figure S2 (Supporting Information).
“The sensors are evaluated in an overview comparison...”.
“. Figure S2 (Supporting Information) demonstrates the test method for determining the breathability of the sensors. The sample was kept on the hand within 5 hours. This skin area is not itchy or discolored when comparing to the beside skin area....”.
Generally, the results according to the hysteresis mentioned in line 46 in the introduction are missing in the paper. (Das Word Hysteresis wird nur einmal im gesamten Paper verwendet.)
Done in the Characterization of the e-fabric skin section (yellow section), Figure 7d,
“Hysteresis is the maximum difference between the output values obtained for the same input value. The small hysteresis properties of the...”.
PRESENTATION
Overall, the text is well written.
Figures 1 shows clearly the manufacturing process.
Some scales in figure 4 need a revision due to poor visibility. Some scales could be printed in black color.
=> Fixed the scale of Figures.
Generally, the letters in the different figures have an different size and appear sometimes as too big (e.g. Figure 4, 6).
=> Fixed the size of letters in the Figures.
The font size and bars in figure 7 are too big.
=> Changed the size of the Figure.
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
In this manuscript, the author presents the simultaneous sensing of touch and pressure by using elastic fabrics based on SWCNT and Ag paste. The system can be utilized to monitor some forms of motion for wearable robotics applications. However, there are some questions should be clarified to improve the quality of this work. The following points were our main concerns and suggestions about this manuscript.
References are required for line 69. In Figure 5b, there are two slopes based on 60 kPa. 2.05*10^-5 kPa-1 is not an exact sensitivity. It is not linear. In the manuscript, there is no explanation in Figure 5e. Figure 5f is explained before 5d. The author need to change the order. It would be helpful to see the sensitivity of the sensor with other studies in Figure 7. Textile electronics has a major limitation. What is the effect of washing?Author Response
Thank you so much for your comments!
Reviewer 3:
Comments and Suggestions for Authors
In this manuscript, the author presents the simultaneous sensing of touch and pressure by using elastic fabrics based on SWCNT and Ag paste. The system can be utilized to monitor some forms of motion for wearable robotics applications. However, there are some questions should be clarified to improve the quality of this work. The following points were our main concerns and suggestions about this manuscript.
=> Added reference [35], [36] in the Reference section.
In Figure 5b, there are two slopes based on 60 kPa. 2.05*10^-5 kPa-1 is not an exact sensitivity. It is not linear.
=> Done in Characterization of the e-fabric skin section, yellow text.
“There are two slopes based on 60 kPa. The pressure sensitivity is 93.3 x 10-4 kPa-1 at 60 kPa, and 205 x 10-4 kPa-1 at 100 kPa. This value depends on the level of pressure...”
In the manuscript, there is no explanation in Figure 5e.
=> Done in Characterization of the e-fabric skin section (yellow text), and Figure 5.
“Besides, Figure 5e also shows the breathable ability of this structure that is impermeable to water and permeable to air....”
Figure 5f is explained before 5d. The author need to change the order.
=> Changed the order of Figure 5.
It would be helpful to see the sensitivity of the sensor with other studies in Figure 7.
=> Done in Characterization of the e-fabric skin section (yellow text), and Figure 8.
“The sensors are evaluated in an overview comparison with other existing works. About the sensitivity, our sensors are higher than two studies [26] (0.283 kPa-1 at 5 kPa), [48] (121x10-4 kPa-1 at 100 kPa), and lower than two studies [34], [49] (0.007 kPa-1 at 5 kPa). About the thickness, our sensors are thinner than those studies as shown in Figure 8. Because of using the spacer fabric, the sensors also have better breathable properties than the reference samples in two studies [34] (using aluminum foil), and [48] (using silicone layers). The spacer layers by the PET yarns will also have more highly elastic than the silicone.”.
Textile electronics has a major limitation. What is the effect of washing?
=> Done in Characterization of the e-fabric skin section (yellow text), and Figure 7.
“Textile electronics have a major limitation, that is the electrode materials (CNTs/silvers) will fall-out after washing. Figure 7c shows the capacitance of the sensors at 100 kPa after a number of washing times. It is clear that the sensors can still work well after 50 washing times. This advantage is mainly caused by the adhesive-ability of silver pastes in order to protect the electrode materials.”.
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Thanks for the revise and I am happy with them.
Reviewer 2 Report
Most of the changes have been incorporated. In my view, there is nothing to be said against an acceptance.
Reviewer 3 Report
I could recommend the publication in this manuscript.
