A Force Measurement Method Based on Flexible PDMS Grating

Round 1

Reviewer 1 Report

The paper describes a simple method for measuring the elasticity of PDMS. The technique is simple even if, as stated by the authors, its range of applicability is limited to soft PDMS (PDMS 1:5 gives unstable results) and to small tensile strength values.

Nevertheless, I think the technique could be interesting for the scientific community working in the field of soft materials.

I recommend the authors thoroughly revise the text of the manuscript (asking for the help of an English native speaker) as it is written in poor English and some sentences seem not to have a clear meaning.

Figure 2 is not an original image but authors copied it from a PhD thesis (easily accessible on the web), so I recommend the authors to cite the source of the image correctly or ask for the permission to use it.

Materials and methods are written with an excess of details, describing steps and procedures that are obvious for people working in the field and for the journal audience, I guess. So I recommend the author to eliminate unnecessary descriptions from those sections. Moreover, Fig. 8 should be eliminated, in my opinion, as the MATLAB workflow has no novelty or added value for the reader but it reports only obvious steps.

Concerning experimental data, it is not clear to me why two graphs (figures 9 and 10) report the same experimental data, one without error bars (figure 9) and one with error bars (but it is limited to a smaller set of data). In figure 11 the numbers reported on the image are too small, and the units are missing. The data reported in Figure 11 are reported without errors, so I ask the authors to estimate and indicate the errors of the measures they report.

In general, the captions are too short and do not clearly explain the figure content.

A reference (page 7) is missing. 

As a general consideration, the paper has been written with a very poor scientific attitude so I recommend the editor not to accept the paper unless major revisions to both text and figures (error bars and captions) are done.

 

 

 

 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper presents the a flexible grating fabricated in PDMS that can be used for measuring force through monitoring the diffraction angle. There are several issues with the paper that would need to be addressed before I could recommend it for publication. 

1) There are several issues with English grammar in the paper. 

2) There are also several instances of the cross-reference for the references being missing leaving a [Error! Reference source not found] warning.

3) The paper should be written in 3rd person. 

4) More references should be used to support the statements in the introduction. 

5) It is not clear what the novelty of the work is. There are many other examples of PDMS gratings in the literature. The authors have referenced Guo et al [8]. which could also be used to measure force. The novelty of the current device needs to be made clear, what advantage is there over other flexible gratings that could also measure force, as force is being inferred from strain.

6)  The methodology needs more clear explanation of how the samples are cut - i.e. how accuracy of dimensions are ensured. What are the errors on the dimensions. Also how is the thickness of the grating set and determined (is it measured)? 

7) Measurement errors and uncertainty should be included in the results. i.e. what is the accuracy of the diffraction spot shift.

8) Figure 12: symbols should be included in the legend or the caption. 

9) The results should be compared to state of the art strain gauges and other sensors in the literature. i.e. how does the accuracy of the force measurement compare to other force sensors.

10) There should be more discussion of the practicality of a sensor that requires line of sight laser illumination and a screen at a fixed distance, to be able to determine the diffraction angle. Also as it is used in transmission mode it can not be stuck onto anything opaque. Is it really usable in real scenarios ?  

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addressed all of my concerns.

I think the manuscript has been significantly improved.