Review Reports

Round 1

Reviewer 1 Report

The authors have carried out very interesting experiments on water droplet behavior when touching the polydimethylsiloxane (PDMS) superhydrophobic cold membrane on which static water contact angle was160 degrees. Using a high-speed camera, they could record 1000 frms/s and observed behavior of the droplets on the different stiffness of the membranes as well the different speeds of the impacting droplets, what is shown on the attached Video as the supplementary material. The obtained results may have an important application to reduce the ice adhesion to different industrial equipment, like radar antennas and others. This is because the authors have found that the droplets can be completely removed from the cold elastic superhydrophobic membranes, what “validate the low ice adhesion”. Although one can have some reservation to the author’s explanations of the droplet behavior (the energy transfer vs. spreading, retracting and rebounding), as long as no other mechanism is proposed the ones given by the authors are acceptable.

168. 167-168. Some ‘justification’ would be worthy to add to the statement “As shown in Figure 6, the surface stiffness has a significant influence on the spreading ratio, which increases (from 2.5 to 2.7) with the increase of membrane stiffness (from 0.65 N/m to 5.21 N/m)”. Is really the change of the spreading ratio by 0.2 significant if the stiffness increases from 0.65 to 5.21 N/m, and a little bit more for the rigid membrane?

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

In this manuscript, the authors investigate the effect of solid substrate's elasticity and wettability on its ice-repelling performance. The manuscript is well written and the experiments seem to be carefully conducted.

The main point of disagreement about this manuscript is that they do not state the limitations of superhydrophobic surfaces under real (not laboratory) conditions. In particular, as referred in Kulinich et al (Langmuir 2010):

"...rough superhydrophobic surfaces are shown not to be always effective anti-ice materials, because of their relatively low abrasive resistance and the inability to deice in all climatic conditions. Though ice accretion on such (“dry”) surfaces can be delayed compared to flat hydrophobic surfaces, when it eventually occurs, it causes a gradual damage of the surface micro-structure during icing and/or deicing. This leads to a gradual decrease in the anti-icing performance. On the other hand, in a humid atmosphere (when water condenses in the rough structure) the icing of such surfaces may lead to very large values of ice adhesion strength (anchor effect)..."

I propose that the authors should state the above limitations in order to make clear that simple superhydrophobic surfaces (or even elastic ones) are not the the "magical" solution for achieving icephobicity.

Furthermore, considering that a little part of the droplet pins on the substrate in the case of the inclined surface (Figure 10), I suspect that the contact angle hysteresis of the fabricated surface is high. The authors should mention the contact angle hysteresis value of their surface, as well as should state the important of hysteresis on icephobicity (see e.g. Nosonovsky & Hejazi [ACS Nano, 2012])

I also have some minor revisions which are listed below:

line 31: "to removal" -> "to remove"

line 32: "are inefficiency" -> "are inefficient"

Overall, I recommend that this article can be accepted for publication, after performing the above revisions.

Author Response

Please see the attachment. 

Author Response File: Author Response.docx