Fingerprint Blurring on a Hierarchical Nanoporous Layer Glass
Round 1
Reviewer 1 Report
The authors presented very interesting results about fingerprint blurring effect on HNL glass. Optical observation and IR-absorption spectroscopy were conducted to analyze the driving force of the blurring effect. The authors concluded that the transportation of fatty acid by capillary force in fine porous regions underneath the surface was the key to the blurring effect. This work is highly original and of potential interest to readers. However, the conclusion is not strongly supported by experimental results, and further improvement could be made. Besides, a few questions and comments need to be addressed.
Figure 1 (a) should be cross-sectional view and (b) should be surface view? The authors need to add a scale bar in Figure 4 (a). It would be useful to provide direct evidence of fatty acid in deeper regions at the spreading ring, such as a cross-sectional mapping of chemical components at the ring area. Capillary action is only a hypothesis rather than a strong conclusion, unless all other types of transportation mechanisms are excluded. For example, the author might want to add an argument that all other types of transportation mechanisms would result in fatty acid on surface region. A theoretical analysis of dependence of capillary force on nanopore size will also help to corroborate the conclusion. Is the HNL glass reusable for fingerprint blurring? If the nanopores have been filled with fatty acid, can it still blur another fingerprint?
Author Response
The reviewer-1 evaluated the authors' manuscript highly original and of potential interest to readers. The reviewer also provided some comments and suggestions to improve the manuscript and enrich the discussion.
At first, we corrected the caption for fig.1 and added a scale-bar in fig.4(a) according to the reviewer's comments. They were our careless mistakes.
The reviewer also suggested that direct evidence of fatty acid in deeper regions at the spreading ring would be useful in this work. Though the authors agree with the opinion, the cross-sectional mapping of chemical components is practically unavailable in this case. The HNL in this work is so thin (less than 500 nm) that the spatial resolution of EDS, for example, is unable to differentiate where the fatty acid exists within the HNL. The authors have added a discussion about the driving force and transportation path of the fatty acid, instead.
According to the reviewer's advice, the authors enriched a discussion in the last part of the manuscript. As the reviewer pointed out, the previous discussion remained just within a hypothesis. We compare two possible mechanisms of the fingerprint blurring: surface diffusion and capillary action with a short comment from the viewpoint of the theory of capillary action.
Finally, the reviewer asked questions about the reusability and quantitative limit. Actually, the authors have some experience that a widely blurred fingerprint on HNL was apparently removed by organic solvent. However, further investigation as to how much amount of fingerprint components remained, whether the blurring occurs alike on the pristine HNL, have not been conducted.
Much amount of fingerprint attachment will also exhibit the blurring on HNL according to the indicated mechanism. Since the capillary action in the deeper region continues widely in the lateral direction, the fatty acid only spreads more widely even in the case of a large amount. There are preliminary experimental results consistent with it. However, capillary action will not work if a tremendous amount of material fills the entire edge of the HNL. Anyway, the limit of the fingerprint blurring is not quantitatively examined yet. The authors, therefore, would like to make detailed results about these topics another article in the near future.
Reviewer 2 Report
The work by Tabata and co-authors, “fingerprint blurring on a hierarchical nanoporous layer glass” is well organized for new functionality of a thin layer of hierarchical nano-porous structure. Please find minor comment as:
In page 2, line 79-80: authors need to provide the superhydrophilicity and optical reflectivity results in the paper or at least a reference if they have previously published. Figure 1: it seems (a) and (b) are cross section view and surface view respectively.Author Response
The reviewer-2 evaluated the authors' manuscript as well organized and gave some comments and suggestions to improve the manuscript.
The reviewer pointed out the necessity to provide the data about the superhydrophilicity and low reflectivity in the HNL characterization. In the revised manuscript, therefore, we refer our previous publication for the superhydrophilicity and have added a reflectivity spectrum as figure 1(c).
Furthermore, we corrected the figure caption for fig.1(a) and (b) as the reviewer pointed out. It was our typo.
Reviewer 3 Report
The manuscript ID:coatings-611830 entitled „fingerprint blurring on a hierarchical nanoporous layer glass, authors Erika Tabata, Takumi Ito, Yuki Ushioda and Takuya Fujima reports the phenomenon of blurring of fingerprints on a modified glass. Manuscript is concise and well written. The experimental data are organized, and the results are presented in the form of tables figures and microscopy images. The conclusions are justified and supported by the experimental data.
I recommend that the paper should be published in the present form, with the suitable modification of title (capital letter at “fingerprint”)
Author Response
The reviewer-3 highly evaluated the authors' manuscript and recommended publication with a title modification.
The authors appreciated the reviewer-3's comments and modified the title capitalizing the letter "f" of "fingerprint."
