4D Printing of Hydrogels Controlled by Hinge Structure and Spatially Gradient Swelling for Soft Robots

Round 1

Reviewer 1 Report

In this manuscript, the authors reported 4D printing of hydrogels controlled by hinge structure and spatially gradient swelling. The authors successfully designed the hinge structure in hydrogels by printing, and analyzed the mechanical properties. this achievement will contribute to the field of soft robotics as well as hydrogel engineering. This reviewer suggest the publication of this manuscript after minor revision. Please consider the following comment to improve the manuscript.

1. The chemical structure of the hydrogel should be provided as Figure. This will be highly useful for the readers in the field of materials science to understand the significance of this work. In addition, please provide the illustration for the ICN gel network structure.

2. The ICN gel was used for the printing. It would be better to discuss why controlling 4D printing of the ICN gel is important, or the merit of ICN gel in the 4D printing technology.

3. The authors investigated the important factors for actuation. The factors can be understandable, however, it is difficult to follow which factors is the most significant. Can the authors discuss the summary of the important factors for actuation? If possible, please consider the summary as Table, and equation if possible.

4. Minor point:

- Figure 1: Please provide the scale bars in the images.

Author Response

Thank you very much for your good evaluation and worthy comments to our manuscript (machines-2101859). We revised our manuscript after considering your helpful comments. Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The novelty should be clearly presented in the abstract.

One of the weaknesses of the abstract is the quantitative results and data that should be added to it.

Move figure 1 to the results section.

Use up-to-date sources in the introduction. The following source is suggested.

https://doi.org/10.1002/adem.202201309

Choose more appropriate keywords. For example, “gradient materials” is not repeated in the abstract, but it is presented as keywords.

Provide more explanations regarding the SEM image used (Figure 2). This section is not complete.

The caption in figure 3 is very long. These explanations should be provided and added in the text.

The research method is very long. If possible, the presentation of parameters in the table should be used to summarize this section.

With what parameters can the swelling ratio be controlled?

How is the validity of the simulation results checked?

The images of actual samples are very small. These images should be presented independently, not in quantitative results.

Author Response

Thank you very much for your worthy comments to our manuscript (machines-2101859). We revised our manuscript after carefully considering your helpful comments. Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

In this study, the effect of parameters such as swelling ratio and Young's modulus on the deformation at different rates in the process of 4D printing of hydrogels controlled by the hinge structure and spatially gradient swelling for soft robots, and their simulation were carried out.

As a result, it was emphasized that the deformation can be adjusted by changing the initiator concentration, crosslinker concentration and thickness. It was concluded that the upper value in deformation was partially estimated and formed an idea for complex structures.

The work is a collective and detailed subject that has not yet been studied in the last few years, on which work has been developed and focused on small goals. Studies are generally on review. Despite the fact that the subject has been studied a lot, focusing on its effect on deformation and discussing its effect on simulation has increased the originality of the study. Although it is foreseen that similar studies will be studied in more detail, it is high expectation that this study will contribute to the literature.

In addition, the study includes applications and presents important results with related methods. Explanation of the buildings with visual materials, the suitability of the software and evaluation tools used stand out.

There are some spelling and grammatical errors eg "5th simulation" needs capitalization and units of measurement need reconsideration.

The number of resources can be increased. Review studies on this subject can be examined and these can be considered as citations.

Its resources should be focused in the last 5 years. It is essential that such innovative topics be supported by more recent citations.

The visual materials are presented very strongly. However, the page layout should be checked again. There are exaggerated dimensions.

Figure descriptions can be explained in more detail. Thus, the reader can approach the picture more selectively.

Author Response

Thank you very much for your good evaluation and worthy comments to our manuscript (machines-2101859). We revised our manuscript after considering your helpful comments. Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Almost all the comments have been answered, and the paper can be published after minor corrections. The quality of the images is excellent, and they can be provided in a smaller size. Reference 36 is also missing, so it is suggested to use this article instead, "A New Strategy for Achieving Shape Memory Effects in 4D Printed Two-Layer Composite Structures".

Author Response

We have made the second minor revisions after carefully considering the helpful comments raised by the reviewer as follows:

“Almost all the comments have been answered, and the paper can be published after minor corrections. The quality of the images is excellent, and they can be provided in a smaller size. Reference 36 is also missing, so it is suggested to use this article instead, "A New Strategy for Achieving Shape Memory Effects in 4D Printed Two-Layer Composite Structures".”

Here we fixed Reference 36 to be new Reference 37, and we add "A New Strategy for Achieving Shape Memory Effects in 4D Printed Two-Layer Composite Structures" as Reference 24. Additionally, we checked that all the references are relevant to the contents of the manuscript, and then we found Reference 17-20 were not relevant and fixed them. All the revised parts are shown in red color in the manuscript.