Microfluidic Sensor Based on Composite Left-Right Handed Transmission Line

Round 1

Reviewer 1 Report

Please address my comments/questions listed below:

Why the operating frequency at 1.275GHz was selected? Fig 3: Please indicate which section is 1) RH microstrip line and 2) CLRH. Also, where are the 3-unit cell of the shunt C and series L? Fig. 5a: The Y-axis is the magnitude of what parameter? Fig. 5b: Can the phase (degrees) be presented with lower values, for example, set 0 degree instead of -200 degrees. Fig. 7 (a & b): Set the same orientation for the schematic diagram (7a) and the photo (7b). Fig. 9:

- Caption: there is a typo: ‘d)’.

- 9a: There are 3 sample sets: TL, epsilon=1, and epsilon=80.1. What are the materials?

- 9b: There are 5 sample sets: epsilon = ~1, ~20, ~24, ~32, ~80. What are the materials? Why didn’t the authors use the same samples for 9a?

Also, since there are just 5 epsilon values, the points should not be connected. Same for Fig. 10.

Author Response

Dear Sir/Madam,

We appreciate the careful reviewing of our manuscript and we gratefully acknowledge the reviewers and editor for their useful comments. We have modified the manuscript to answer the questions raised by the reviewers. Our answers, some additional comments and explanations are given in the text below and the changes are made in the resubmitted manuscript.

We thank you for the opportunity to improve our paper, including your comments and suggestions.

Sincerely,

The authors

Reply to the Reviewer’s Comments

 

Answers to the First Reviewer

Comment 1:

Why the operating frequency at 1.275GHz was selected?

Authors’ response:

According to the Reviewer’s valuable remarks, authors would like to give a more detailed clarification, explained in [1] in more details:

The main advantage of the phase-shift method lies on the fact that on the frequencies high enough, the influence of conductivity to the phase response can be neglected.

Complex propagation constant for lossy medium can be expressed as:

                                                (s.1)

where µ, ε and σ are the real parts of the permeability, permittivity, and electrical conductivity of the medium through which the signal is propagating, respectively. If the imaginary part of the complex propagation constant is known, the phase velocity can be determined as:

                                                              (s.2)

Based on Eq. (s.2) it can be seen that phase velocity is dominantly influenced by permittivity, permeability and signal frequency, and then electrical conductivity.

Is the frequencies high enough, the influence of conductivity can be neglected:

                                                                           (s.3)

and therefore, expression for velocity on high frequencies can be reduced to:

                                                                           (s.4)

where phase velocity is determined by permeability and permittivity only.

On the other hand, in order to apply standard electronics components in the design of the detection circuit, the frequency is chosen to be high enough to eliminate the conductivity effect but low enough to apply standard phase comparator.

According the reviewer valuable comment we includes additional explanation in the resubmitted manuscript, L185-L187

Comment 2:

Fig 3: Please indicate which section is 1) RH microstrip line and 2) CLRH. Also, where are the 3-unit cell of the shunt C and series L?

Authors’ response:

According to the Reviewer’s valuable remarks, the Figure 3 was replaced with the new one in which we marked the specific parts of the proposed sensors, such as Wilkinson power divider, RH section, CLRH section and unit cell.

Comment 3:

Fig. 5a: The Y-axis is the magnitude of what parameter? Fig. 5b: Can the phase (degrees) be presented with lower values, for example, set 0 degree instead of -200 degrees.

Authors’ response:

In response to the Reviewer’s valuable comment, the Y-axis in Fig 5a (now Figure 6 in the resubmitted manuscript) was corrected. The results proposed in Figure 5b are Unwrapped phase of the transmission characteristic of the RH and CLRH sections. The phase difference can also be shown in a different, normalized range (as suggested by the reviewer) or as a standard ranging from -180 to 180 degrees. However, proposed mode in the best way reflects the phase changes over the frequency and therefore it is selected.

Comment 4:

Fig. 7 (a & b): Set the same orientation for the schematic diagram (7a) and the photo (7b)

Authors’ response:

We would like to thank reviewer for point that out. Figure 7 (now, Figure 8 in the resubmitted manuscript) was replaced with new one.

Comment 4:

Fig. 9:- Caption: there is a typo: ‘d)’.

Authors’ response:

We appreciate this comment. We believe that revised manuscript is better in this context, bearing in mind that we have performed carefully proof-reading.

 

Comment 5:

9a: There are 3 sample sets: TL, epsilon=1, and epsilon=80.1. What are the materials?

9b: There are 5 sample sets: epsilon = ~1, ~20, ~24, ~32, ~80. What are the materials? Why didn’t the authors use the same samples for 9a?

Also, since there are just 5 epsilon values, the points should not be connected. Same for Fig. 10.

Authors’ response:

Thank you for this comments. In Figure 9 (now, figure 10 in the resubmitted manuscript) we compare the simulated and measured results. As was add in the text above the epsilon=1, and epsilon=80.1 correspond the air and water inside the channel, respectively. In addition, the results proposed in the Figure 9a shows only two marginal values, while the results proposed in Figure 9b shows the phase shifts for different fluids inside the channels. Due to the vast number of curves, we decide to use such presentation. Good agreement between measurements and simulations was demonstrated in Fig. 9a for marginal values, while phase shift responses for different fluids inside the microfluidic channel are shown in Fig. 9b. The displaying of all the curves for different fluids in Figure 9a would cause total confusion and the results would not be clearly visible.

The dielectric constants of 1, 2.2, 19.7, 24.5, 32 and 80.1 correspond to different fluids, namely Air, Oil, Isopropanol, Ethanol, Methanol and Water, respectively. To make this clearer we add in new Fig. 6 all values of the dielectric permittivity and tangent loss factor used in simulations.

We agree with the reviewer for the third comments related to the connection of the points. We remove the interconnection between points in Figures 9b, 10, and 11 (now Figure 10b, 11, and 12). In addition, additional fitting curve and equation were added to figures 11 and 12 that modelled their linear approximation.

The following lines were included in the resubmitted manuscript: L211-L214, L222-L224.

Author Response File: Author Response.pdf

Reviewer 2 Report

The submitted manuscript "Microfluidic Sensor based on Composite Left-Right Handed Transmission" reports a microfluidic sensor by measuring the phase difference between a referent microstrip line and CLRH microstrip line. There are some concerns as listed below.  

The authors didn’t mention any physics of the proposed CLRH microstrip line. More discussions should be given for the CLRH line. The authors attribute the phase shift to the change of the real part of permittivity. Can authors comment on the imaginary part of the permittivity? Does the change of the imaginary part of permittivity contribute to the phase shift? Some minor typo error should be corrected. “negative permeability, permeability…” should be “negative permittivity, permeability...” in line 34 page 1, “their comparison with a results…” should be “their comparison with results…” in line 210 page 7. It is suggested to add the following relevant papers to the reference in order to give the general audience a more complete and contemporary reference of the microfluidic metamaterials. such as Doi.org/10.1002/adom.201601103, and Doi.org/10.1063/1.4985288.

In conclusion, the manuscript can be re-considered after the above questions are well addressed.

Author Response

Dear Sir/Madam,

We appreciate the careful reviewing of our manuscript and we gratefully acknowledge the reviewers and editor for their useful comments. We have modified the manuscript to answer the questions raised by the reviewers. Our answers, some additional comments and explanations are given in the text below and the changes are made in the resubmitted manuscript.

We thank you for the opportunity to improve our paper, including your comments and suggestions.

Sincerely,

The authors

Reply to the Reviewer’s Comments

Answers to the Second Reviewer

Comment 1:

The authors didn’t mention any physics of the proposed CLRH microstrip line. More discussions should be given for the CLRH line.

Authors’ response:

We really appreciate this comment. In the resubmitted manuscript authors provide more detail about physics of the proposed CLRH line, explain its equivalent circuit and explain how the geometrical parameters influences to the phase response.

The following lines were included in the resubmitted manuscript: L150-L179, as well as additional figure, Figure 4 was added.

 

Comment 2:

The authors attribute the phase shift to the change of the real part of permittivity. Can authors comment on the imaginary part of the permittivity? Does the change of the imaginary part of permittivity contribute to the phase shift?

Authors’ response:

We really appreciate this comment. The imaginary part of the complex permittivity does not affect the phase shift but can influences the amplitude of the signal and insertion losses [1]. The imaginary part of the complex permittivity cannot be directly calculated from the phase shift and therefore the measurement of the amplitude of two signals should be taken into account in order to calculate the imaginary part. The imaginary part can be also calculated using Kramers-Kroning relation [1]. Since the used Phase comparator allows also measurement the amplitude difference between referent and measurement signal, this signal can be used for estimation of the imaginary part of the complex permittivity as well as for the mitigation of the comparator measurement error of the phase shift. Some additional explanations were included in the resubmitted manuscript. Some additional explanation is given in resubmitted manuscript L270-276.

Comment 3:

Some minor typo error should be corrected. “negative permeability, permeability…” should be “negative permittivity, permeability...” in line 34 page 1, “their comparison with a results…” should be “their comparison with results…” in line 210 page 7.

Authors’ response:

We appreciate this comment. We believe that revised manuscript is better in this context, bearing in mind that we have performed carefully proof-reading.

Comment 4:

It is suggested to add the following relevant papers to the reference in order to give the general audience a more complete and contemporary reference of the microfluidic metamaterials. such as Doi.org/10.1002/adom.201601103, and Doi.org/10.1063/1.4985288.

Authors’ response:

We agree with this comment. In the revised manuscript the following references were added.

 

[7] Song, Q.; Zhang, W.; Wu, P. C.; Zhu, W.; Shen, Z.X.; Chong, P.H.J.; Liang, Q.X.; Yang, Z.C.; Hao, Y.L.; Cai, H.; Zhou, H.F.; Gu, Y.; Lo, G.‐Q.; Tsai, D.P.; Bourouina, T.; Leprince‐Wang , Y.; Liu, A.‐Q. Water‐Resonator‐Based Metasurface: An Ultrabroadband and Near‐Unity Absorption, Advance optical materials, 2017, 5, doi.org/10.1002/adom.201601103.

[8] Song, Q.H.; Zhu, W.M.; Wu, P.C.; Zhang, W.; Wu, Q.Y.S.; Teng, J.H.; Shen, Z.X.; Chong, P.H.J.; Liang, Q.X.; Yang, Z.C.; Tsai, D.P.; Bourouina, T.; Leprince-Wang, Y.; Liu, A.Q. Liquid-metal-based metasurface for terahertz absorption material: Frequency-agile and wide-angle. APL Materials, 2017, 5, doi.org/10.1063/1.4985288.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Please address the following comments:

On line 186: Change the word ‘small’ to ‘low’. Figs. 5, 6 and 10, for black and white printing, the authors should plot the data using different patterns, e.g. solid, dotted, dashed, etc., besides using different colors. Fig. 7, a ruler or dimensions should be added to the photo in order to show the structure size/dimensions. To further improve the article, the authors should also add the most recent relevant papers to the references in order to give the general audience a more complete and updated list of references for MTM-based microfluidic sensors, such as: N. Wongkasem and M. Ruiz, "Multi-Negative Index Band Metamaterial-Inspired Microfluidic Sensors," Progress In Electromagnetics Research C, Vol. 94, 29-41, 2019.
doi:10.2528/PIERC19041503, and  Zhou, H., D. Hu, C. Yang, C. Chen, J. Ji, M. Chen, Y. Chen, Y. Yang, and Z. Mu, “Multiband sensing for dielectric property of chemical using metamaterial integrated microfluidic sensor,” Scientific Reports, Vol. 8, 14801, 2018.

 

Comments for author File: Comments.pdf

Author Response

Dear Sir/Madam,

We appreciate the careful reviewing of our manuscript and we gratefully acknowledge the reviewers and editor for their useful comments. We have modified the manuscript to answer the questions raised by the reviewers. Our answers, some additional comments and explanations are given in the text below and the changes are made in the resubmitted manuscript.

We thank you for the opportunity to improve our paper, including your comments and suggestions.

Sincerely,

The authors

Reply to the Reviewer’s Comments

 

Answers to the First Reviewer

Comment 1:  On line 186: Change the word ‘small’ to ‘low’.

Authors’ response:

Thank you for point that out.

Comment 2: Figs. 5, 6 and 10, for black and white printing, the authors should plot the data using different patterns, e.g. solid, dotted, dashed, etc., besides using different colors. Fig. 7, a ruler or dimensions should be added to the photo in order to show the structure size/dimensions.

Authors’ response:

According to the reviewer valuable comment we change mentioned Figures in the resubmitted manuscript. In Figures 5, 6, and 10 we plot curves using different symbols, while in Figures 7 and 8b we add rulers.

Comment 3: To further improve the article, the authors should also add the most recent relevant papers to the references in order to give the general audience a more complete and updated list of references for MTM-based microfluidic sensors, such as:

Wongkasem and M. Ruiz, "Multi-Negative Index Band Metamaterial-Inspired Microfluidic Sensors," Progress In Electromagnetics Research C, Vol. 94, 29-41, 2019. doi:10.2528/PIERC19041503,

Zhou, H., D. Hu, C. Yang, C. Chen, J. Ji, M. Chen, Y. Chen, Y. Yang, and Z. Mu, “Multiband sensing for dielectric property of chemical using metamaterial integrated microfluidic sensor,” Scientific Reports, Vol. 8, 14801, 2018.

Authors’ response:

According to reviewer valuable suggestion we include second reference in the text together with some recently published references related to the metamaterial-based sensor. However, the first reference is based on simulation only and we believe it is not relevant to our work.

[a1] Vivek, A.; Shambavi, K.; Alex, Z.C. A review: metamaterial sensors for material characterization. Sensors Review. 2019, 39. Doi: 10.1108/SR-06-2018-0152

[a2] Zhou, H.; Hu, D.; Yang, C.; Chen, C.; Ji, J.; Chen, M.; Chen, Y.; Yang, Y.; and Mu, Z. Multiband sensing for dielectric property of chemical using metamaterial integrated microfluidic sensor. Scientific Reports, 2018, 8. Doi: 10.1038/s41598-018-32827-y