Natural Flexible and Responsive 2D Photonic Materials with Micro-Sandwich Structure

Round 1

Reviewer 1 Report

This manuscript by Pan et al describes a study of natural biomaterials (molluscs shells) with responsive photonic properties. The materials are interesting due to the "non-iridescent" nature of scattered light from a polydisperse array of pore-like structures. I find the content and context of this paper to be highly suitable for the MDPI Photonics journal.

There are a number of examples of analogous engineered photonics materials, where some effects of non-resonance scattering from a significantly disordered structure may play a role, and I think the paper would benefit from discussion and citation of these? Examples might include the work of Baumberg et al (e.g. "polymer opals"), and M. Kolle.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Photonics 2092896 peer review v1

Natural flexible and responsive 2D photonic material with micro-sandwich structure

Overview and general recommendation:

In this manuscript the authors theoretically and experimentally study the origin of the colour reflected from the periostracum of Green lipped mussel (Perna canaliculus). They claim that they first find the exterior green colour is resulted from the 2D amorphous photonic structure in the central layer of periostracum. I think the manuscript is overall well written, and the authors also systematically demonstrated many observation results. However, just to my point of view, two basic questions need to be clarified before considering this manuscript. Therefore, I would recommend that a major revision is warranted. I explain my concerns in more detail below.

 Major comments:

1. The authors claim that the parallel proteinous nano fibers are the main components of the 2D amorphous photonic structure, which reflects the exterior green colour. However, the SEM images (Figure 3) show that the uniformity of these nano fibers should be not good. That is, the effects of the variations of (1) the curvature of these nano fibers, (2) the parallelism between the nano fibers, and (3) the separation between the nano fibers should be considered. The authors must give some discussion about these issues.

 2. In this manuscript there is almost no description of the theoretical study for the photonic crystal. What we can find are from Line 105 to 108, in Line 206 and 207, and the predicted results, Figure 6 (B). In fact, as shown in Figure 5 (A), the parallel proteinous nano fibers is far from a perfect 2D photonic crystal. Besides, as I mentioned above, the uniformity possibly is not good. How to simplify and transform this complex nano fiber structure into a computable 2D photonic crystal is an important and inevitable task. If possible, please describe your work of this task.

Besides, I have some secondary comments as follows:

1.      The “A-A’ ” is mentioned in Line 71 and Line 129, but I do not find “A-A’ “ in Figure 1 (A).

2.      As far as I know, the Bragg diffraction is dependent on the incident and exit angles of light. However, as shown in Figure 1, the exterior green colour is omnidirectional. Please explain this phenomenon.

3.      As shown in Figure 1 (A), the exterior colour of most periostracum is not green. Is there proteinous nano fibers in the non-green periostracum?

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx