Review Reports - Inkjet-Printed Reflectarray Antenna Integrating Feed and Aperture on a Flexible Substrate Using Origami Techniques

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. The source of the ink is not clear. The ink's model, brand, and ink manufacturer should be provided. What's the ink rheological property?

2. The source of the PEN substrate is not clear as well. What is the surface free energy and the surface roughness condition?

3. The authors provided adequate information for the design of the antenna. However, the information about the manufacturing process of the antenna is still lacking, for example, the post-processing parameters such as the sintering temperature and duration are not discussed.

4. What's the resultant film thickness and the electrical conductivity of the printed film post-sintering?

5. PEN has a glass transition temperature of 120 deg Celcius. What sintering temperature was used?

5. Inkjet printing technique is a very common and established electronic printing technique. The authors should justify why inkjet printing is essential for the application. What's the contribution of this work to the scientific community? How does inkjet printing compare to other electronic printing method such as aerosol jet printing (AJP), direct ink writing (DIW), electrohydrodynamic printing (EHD)?

a. AJP: G. L. Goh, S. Agarwala, and W. Y. Yeong: 'High Resolution Aerosol Jet Printing of Conductive Ink for Stretchable Electronics', Proceedings of the 3rd International Conference on Progress in Additive Manufacturing (PRO-AM), Nanyang Technological University, Singapore, 2018, 109-114.

b. DIW: Castelló-Palacios, S., Antonino-Daviu, E., Vila-Jiménez, A., Vallés-Lluch, A., Cardona, N., & Garcia-Pardo, C. (2023). Tailored EM Materials for Millimeter-Wave Direct Ink Write Printed Antennas. IEEE Access.

c. EDH: Wu, Y., Fu, C., Qian, S., Zong, Z., Wu, X., Yue, Y., & Gu, W. (2020). Flexible and transparent W-band absorber fabricated by EHD printing technology. IEEE Antennas and Wireless Propagation Letters, 19(8), 1345-1349.

6. What the waveform used for the ink droplet ejection? how was the optimization done?

7. how many print passes/overprinting was done?

Comments on the Quality of English Language

nil

Author Response

Thank you for your feedback and comments.

We have carefully considered and addressed all the reviewers' comments. The necessary revisions have been made to the manuscript to enhance its clarity, comprehensiveness, and overall quality. The manuscript has been heavily revised to incorporate all suggestions. We have uploaded the revised manuscript and the detailed reply to the reviewers as a PDF file. We kindly ask the reviewers and the Associate Editor to review the attached PDF file for a comprehensive overview of the changes made.

Thank you once again for your valuable feedback and for facilitating the review process.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study outlines the design and performance evaluation of an inkjet-printed reflectarray antenna, discussing its structure, fabrication process, and results. However, there are several major concerns regarding this manuscript. The authors can consider the following;

1) The title is misleading as it claims an "inkjet-printed origami reflectarray," when in reality only the feed and aperture are printed using inkjet technology. To accurately represent the content, the title should be revised accordingly.

2) The authors state that that “This paper presents an innovative method for fabricating reflectarray antennas using inkjet printing technology on flexible substrate”. However, this method is already well-established and its feasibility for antenna production has been extensively reported in the literature. Considering that the inkjet printing is not carried out on the deployable surfaces of the origami design, the reviewer cannot see any distinction between this study and the conventional offline assembling of the reflectarray within the origami structure.

3) The origami-based reflectarray designs were also reported by the authors in their previous work. https://doi.org/10.1109/TCPMT.2024.3376351.

4) The manuscript heavily focuses on inkjet printing, but there is a lack of investigation into the parametric effects of inkjet printing on the final result. Details regarding other factors affecting deposition, such as ink rheological properties and kinematic settings, should be included to provide a comprehensive understanding of the process.

5) Since the printing is performed on a flexible substrate (PEN), it is crucial to report the relative resistance change of the conductive printing after bending cycles. This assessment is necessary to prove the reliability and durability of the printed antenna, especially during the self-deployment stage where the antenna may undergo mechanical stress.

6) The manuscript does not clarify the method of coupling the feed unit to the reflectarray. Mechanical coupling details regarding the feeding mechanism should be provided.

7) Figure 16 does not depict the printed reflectarray. It is necessary to clearly indicate the printed reflectarray in the figure for better visual comprehension.

8) The post-heat treatment process needs further clarification. Details such as the post-sintering temperature, duration, and any potential compromise in the adhesion strength of the printing should be included to ensure an understanding of the fabrication process.

9) The glass transition temperature of the PEN substrate material is approximately 120°C, which may limit the practical applications of this antenna in various fields. The implications and potential challenges resulting from this limitation should be explicitly discussed.

10) With a total of 19 figures, the manuscript becomes challenging to read and comprehend. The authors should consider compiling relevant figures together to streamline the presentation and improve readability.

11) A schematic illustrating the printing strategy can be provided for a clear visual representation of the process.

Overall, the biggest concerns about this manuscript are: (i) the origami sections of the reflectarray do not include any printing, which contradicts the practical application of origami reflectarrays, and (ii) there is a lack of systematic investigation into the ink-jet printing process for fabricating the reflectarray.

Author Response

Thank you for your feedback and comments.

Thank you once again for your valuable feedback and for facilitating the review process.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper introduces a 3-D printed foldable reflectarray antenna that integrates the feed source and reflectarray aperture on a flexible substrate. Simulated and measured results are given to demonstrate the concept and design. While the design is interesting, the main concern is the large discrepancy between the simulated and measured antenna performance. Some comments:

1. The abbreviations of PET, PEN, and PI should be explained in their first appearance in the paper.

2. Check the sentence in line 240, “The radiation performance”.

3. The patch antenna in Fig. 4a is fed in the corner. What is the polarization of the patch antenna?

4. Please elaborate on why the measured cr-pol level is much higher than the simulated one in Fig. 7.

5. The simulated insertion loss of the reflectarray element is 2.91 dB. Is the loss caused by the substrate or the low conductivity of the printed conductor layer?

6. The measured aperture efficiency of the two reflectarray antennas should be given.

7. There exists a large discrepancy between the simulated and measured radiation patterns. Please elaborate on the reason.

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

Thank you for your feedback and comments.

Thank you once again for your valuable feedback and for facilitating the review process.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Please see the file attached.

Comments for author File: Comments.pdf

Author Response

We would like to thank the reviewer for the insightful suggestions on our manuscript. The manuscript is now heavily revised as per the comments provided by the reviewer. Please see the attachment for our detailed responses.