Photo-Responsive Liquid Crystal Elastomer Coils Inspired by Tropism Movements of Plants

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors present a very interesting work in LCE coiling actuators for artificial muscles. Plant-mimetic actuators have long been a field of interest in soft robotics research.

The introduction is appropriate and clearly shows the history of the field while outlining the novelty of the paper  by finding a gap in the literature, namely the assertion that "Although several types of light-responsive LCE have been reported in the literature these materials were either too soft or too small displaced."

This assertion however comes at a cost; for the authors to prove the originality of the paper they then have to prove that their own LCE actuator is stiff and capable of wide displacement.

The authors perform no mechanical characterization of the actuator other than a visual assement of linear strain that they estimate is around 30%, this is insufficient. A study of Work Density of the actuator would thus be highly recommended. And furthermore, a comparison table comparing the linear strains, young's moduli and Work Density of the present work to those of the state of the art would be warranted, since the main assertion of novelty is a quantitative improvement over the state of the art.

To estimate the Young's Modulus, classic testile testing or DMA of the material will suffice. With this experimental information it would be possible to extract the true linear strain from the bending angle using Timoshenko-Ehrenfest Beam Theory. And with this, Work Density would be trivial to calculate, leading to a quantifiable measure of the actuator's force, with which it can be quantitatively compared with the literature.

This is but one possible approach of course, but the need to have a true quantifiable comparison with the literature is essential for a work whose main claim is a quantitative improvement over the state of the art.

The work is original and its results interesting, it would be a shame to not see it published, but substantial further work is needed in characterizing the interesting results obtained.

Author Response

please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is well-written. The work and results given in the manuscript are sufficiently novel and significant for publication in Actuators. However, the manuscript needs improvement before its formal publication.

(1) The core part of the manuscript is the extrusion rolling process described in Fig. 1b. More details need to be provided for its description and understanding. Some of the information shown in Fig. S1 needs to be brought back into the main text. Giving more information, or comments, on the parametric studies, such as the impacts of the rotation speed, mandrel thickness, and maximum achievable device dimensions, will greatly help the readers. 

(2) The bending mechanism in Fig. 4c is unclear. It is understandable that the V-deformation of the molecule can lead to contraction of the whole structure. But why is it leading to bending as well? The figure itself seems insufficient. 

(3) The reviewer thinks that the work's relation to the plant tendril structure is marginal at best. It just showed up in the title, very briefly mentioned in the introduction, and not much more (referring just to a video is not sufficient). If the source and implication of the tendril-inspiration could not be further elaborated, it should be removed. 

(4) Are Fig. 1c(i) and Fig. 1c(ii) showing the same device? If not, please clarify.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

While it is unfortunate that the authors were unable to perform the relevant mechanical characterization of the actuator, the work itself shows an original approach and shows interesting results, meriting publication. Given the publication constraints given to the authors and the corrections made by the authors in light of the peer review, I would indeed recommend this work for publication.