Unexpected Frictional Behavior of Laser-Textured Hydrophobic Surfaces
Round 1
Reviewer 1 Report
My congratulations to the authors for this very successful work, which combines experimental and theoretical / simulative tribology in an excellent way and investigates the 'right' questions. From my point of view, only minor changes / additions might be made, the suggestions can be found as comments in the attached PDF file.
Comments for author File: 
Comments.pdf
Author Response
Please find our answers in the attached document.
Author Response File: Author Response.pdf
Reviewer 2 Report
The authors investigated the effect of surface texturing on the frictional behavior of PTFE vs. glass in water-lubricated conditions. Specifically, the authors machined cavities by laser ablation. In comparison with an untextured surface, the authors observe an increase in the friction coefficient. They discuss their observation based on the build-up of high pressure in the liquid and the formation of vortices inside the cavities. In the reviewer's understanding, the formation of vortices should both depend on the size of the cavities and the sliding velocity. It would be helpful if the authors show the velocity dependence of friction for different sizes of the cavities. This may however require recording the friction behavior at intermediate velocities. Also, providing plots of friction versus the sliding distance is desirable, since it could shed light on the sliding mechanisms at play. While the interpretation of the results appears reasonable, it remains too speculative. I thus recommend the article to be reconsidered for publication after revision.
Author Response
Please find our answers in the attached document.
Author Response File: Author Response.pdf
Reviewer 3 Report
In this contribution by Jendoubi and co-workers, the authors examined unexpected frictional behavior of laser-textured hydrophobic surfaces. The results are interesting and potentially attractive to the readership of Lubricants. Overall, I judge this should be published, subject to some minor revision as below.
- Line 81, ‘107 o and 112 o’ should be changed to ‘107o and 112o’.
- Figure 1, it is difficult to see the numbers in the figure.
- The authors should make it clear in the ‘materials and methods’ that what is the lubricant and what is the counter surface for fiction measurement. It is better not to let the reader to look for such important information.
- What is the pressure between the surfaces?
- In the introduction or discussion, it is worth mentioning that in boundary lubrication regime, the fiction coefficient between hydrophobic surface and hydrophilic surface could be very low (in super-lubrication regime) due to hydration lubrication mechanism. In that case, it is reasonable that the fiction coefficient of rough surface is higher that of smooth surface since it is in boundary lubrication regime. While in this study, the authors should emphasis it is in hydrodynamic lubrication regime therefor the phenomenon is unexpected. Some references (doi.org/10.1021/acsnano.8b04735; doi.org/10.1016/j.cocis.2019.10.001) should be included related to this discussion.
Author Response
Please find our answers in the attached document.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors convincingly answered the comments raised during the review process. I recommend accepting this manuscript.
