A Novel Love Wave Mode Sensor Waveguide Layer with Microphononic Crystals

Round 1

Reviewer 1 Report

In this manuscript, Authors have reported a new design rule for Love sensors to overcome previous issues and thus extending their application fields.  To this end, Authors proposed a structure of waveguide layer with micro photonic crystals and theoretically investigated their characteristics. Finally, Authors demonstrate the theoretical results with experiments. Overall, the manuscript is readable and well written. I believe the manuscript will provide access to simple and versatile design rules to improve Love sensors. I suggest Authors address the following comment, then I would be happy to recommend the publication in Applied Science.

1. I suggest Authors provide more information regarding Love sensor in Introduction for general readership.
2. I found typos in the manuscript that should be corrected. (e.g., In page 5, line 165, “Thus quasi-three-dimensional FEM (FEM?)…”)
3. Authors have stressed the applicability of Love sensor in aqueous condition. If I understand correctly, however, characteristics of their device (Fig. 8) was not explored in the aqueous condition. It would be of interest to provide the relevant result.

Author Response

Author Response File: Author Response.docx

Reviewer 2 Report

Manuscript presents some theoretical and experimental results on Love sensors with an embedded micro patterned structure of Al. The study could be of a potential interest, but there are some clarifications and corrections needed in the manuscript. Here are several:

Introduction

“Usually the wave in the piezoelectric wafer propagates perpendicular to the X-axis”

- Axis are not defined by the authors

“On the other hand, piezoelectric phononic crystals (PnCs) [19] are periodic elastic structures consisting of two different elastic materials, which have the band gaps.” ???

Materials and methods

“The structure is as shown in the Figure 1, the Al cylinders have the period of 20 um and the

diameter of 10 um”

- Represented model is not with cylinders !. There is a rectangular section represented !

“The finite element method is used to analyze the energy band structure, namely, the eigenvalue character.”

- What is the geometrical model used and what are the frontier boundaries after all ?

- Does the model consider an inter-diffusion between the materials or is a “theoretically” sharp edge between them ?

3 Experiment and Results

“From the Figure 9, we can see that with introducing the designed micro structure of phononic

crystals in the propagation path, the attenuation is barely increased and the frequency is just shifted

a little”

- It is not clear to me what shift the authors are actually talking about. Furthermore I would have prefer to see the overlap of the theoretical and experimental results of the same structure and the authors to comment on the origin of the differences.

4 Discussion

The chapter is probably intended to be the “Conclusion” chapter

Serious English revision needed ( e.g. - “Furthermore, experiments verify the results of new intruding of micro PnCs can achieve no serious disturbance of attenuation”, and there are many other examples).

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript is nowhere close to ready for submission or in a readable form. The authors need to work out the layout and focus of the manuscript first, what is the intention of the paper? What's the purpose of describing P-Matrix? why has the FEM simulation been done?  There is no clarity in the entire manuscript except the first few paragraphs in the Introduction. 

I see there is the prospective result on integrating PnCs with the Lovewave mode SAW device, the authors should now consider the focus only on fabrication and subsequent fluid sensing.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The manuscript was indeed improved, but at least the simulation part and results interpretation still rises some question marks to me, and I will emphasize two aspects:

1) If the authors are talking about “finite element” approach, but in their response are mentioning using one “single cell” to model (more likely in a quasy-periodic mesh structure I guess ???) However, since they are presenting a non-homogenious structure it is still not clear to me HOW this cell is containing the embedded photonic crystal (geometrically speaking) and after all why they are talking about a “finite element model” with a single-cell symmetry approximation

2) Authors are mentioning in their response that it is not possible to place together the simulation results and experimental since their are “not very well matching”. In my opinion the idea of a simulation is actually to match the experimental results and try to have a model and a better understanding of the experimental results. If this is not the case, I see not much sense of the simulation. Thus, unless there should be a reasonable correlation between the experimental and simulation results, I would suggest the authors either to improve the model to match the existing results, or to keep only some theoretical consideration about obtained results which briefly explain the results rather then an unclear model with non-matching results.

Author Response

Please see the attachmen

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript is improved a lot from the previous version, some more revisions are needed, following are my suggestions

1. Fig. 4 shows multiple curves and the authors just mention merely there is no band gap below 200 MHz. The discussions are insufficient. Clearly explain the curves, x-axis ranges, how the reader can understand there is no band gap. 
2. Fig, 6 results, explain in text how Y21 was calculated from FEM. 
3. Authors have mentioned Love Sensor or Love delay line. I believe it should be “Love wave mode” instead of just Love.
4. Fig. 10 (a) is not at all clear, provide a clear picture. Also, all the figures in Fig. 10, provide scale.
5. Fig. 12(b) shows an N/W analyser that is in OFF condition, keep the equipment ON and take the picture else there is no point in showing the picture. 
6. The experiment was done using only a 2uL sample, how abt few more like 4 uL, 8uL, 10uL then it can provide more clear trend for the proposed application. Then a plot of S12 can be shown for all these samples. 

Author Response

Please see the attachmen

Author Response File: Author Response.docx

Round 3

Reviewer 3 Report

The authors have revised the manuscript and addressed my comments. The manuscript may be considered for publication.