Investigations of Adhesion under Different Slider-Lube/Disk Contact States at the Head–Disk Interface
Round 1
Reviewer 1 Report
Brief summary
The authors are intensively working on a numerical adhesive contact model for the TFC slider-disk interface based on the Lifshitz theory. Therefore a handling of various recording status including the flying state, lubricant contact state and solid contact state, are examined. As well as the adhesive contact characteristics of the HDI the presence of thin lubricant and DLC layers and further effects are examined.
Broad comments
The overall paper is very well and precisely written. A detailed overview on the state of knowledge seems to be given. The paper and description of the methods are intensively structured especially the conclusion.
Thanks to the authors for sharing this specific insight.
There are no specific comments.
Author Response
Reviewer's Point: There are no specific comments. 

Author's Response: Thank you very much for reviewing our manuscript.
Reviewer 2 Report
The manuscript under review looks to be of scientific and practical interest. It is well organised and clearly written. It can be recommended for publication after performing a language check and text formatting. Best regards!
Author Response
Reviewer's Point: The manuscript under review looks to be of scientific and practical interest. It is well organised and clearly written. It can be recommended for publication after performing a language check and text formatting.

Author's Response: Thank you very much for your kind suggestions. We have revised the whole manuscript carefully in terms of the language. Furthermore, the text is re-formatted according to the journal guidelines.
Reviewer 3 Report
The author conducted numerical calculation for the adhesive contact model of the TFC slider-disk interface. The research was well designed and explained. Few points should be addressed before acceptance.
- What is the type of lubricant the author used in the model?
- Can the author provide the operation condition? If the system was modeled in the ambient air, does the author expect any adsorption of water? In this case, the meniscus of the adsorbates may affect the adhesion.
- Was the system simulated under the static condition? What does the author expect for the dynamic condition? How does the sliding or rotation speed affect the model?
Author Response
Point 1: What is the type of lubricant the author used in the model?
Response 1: Thank you very much for your kind reminder. The solid-like perfluoropolyether (PFPE) type lubricant is used in the present simulation. This point has been added in line 124 in Section 2.1.
Point 2: Can the author provide the operation condition? If the system was modeled in the ambient air, does the author expect any adsorption of water? In this case, the meniscus of the adsorbates may affect the adhesion.
Response 2: Thank you very much for this thoughtful comment. The operation condition is in the dry air, which has been added in line 120 in Section 2.1. We agree with the reviewer that if the system is modeled in the ambient air, the adsorption of water and effects of the meniscus of adsorbates on the adhesion may become significant. Two previous experimental studies provide some conclusions. Brunner [1] measured the adhesion on PFPE-lubricated magnetic recording disks using AFM in the ambient air and results of the measurements showed that there was no evidence for meniscus formation at the contact. Liu et al. [2] studied effects of humidity on the adhesion properties of PFPE films by AFM. It was found that for PFPE film having polar (Z-DOL) surface terminal groups, because of their hydrophobic surface properties, only at high humidity (relative humidity≥45%) water molecules could be adsorbed and caused an increase in the adhesive force. From these studies, we may conclude that the effects of water adsorption should be considered at high humidity. The reviewer provides us a meaningful research idea for the future work.
[1] Brunner R, Tyndall GW, Waltman RJ, Talke FE. Adhesion between surfaces separated by molecularly thin perfluoropolyether films. Tribology Letters. 2020, 40, 41-48.
[2] Liu HW, Bhushan B. Nanotribological characterization of molecularly thick lubricant films for applications to MEMS/NEMS by AFM. Ultramicroscopy. 2003, 97, 321-340.
Point 3: Was the system simulated under the static condition? What does the author expect for the dynamic condition? How does the sliding or rotation speed affect the model?
Response 3: Thank you very much for your thoughtful guidance. The present model is established for the HDI under the static condition, which has been added in line 18 in the abstract, line 110 in Section 1 and line 121 in Section 2.1. Considering the adhesion force predicted by the present model, and coupling with the air-bearing forces, the preload of the suspension and the friction force, the dynamics equation of the head-gimbal-assembly can be established. The rotation speed of the disk has no direct effects on the adhesion force at the HDI. However, it can affect the air-bearing forces directly, thus influence the flying height and as a result influence the adhesion force [3]. Dynamic analysis will be conducted in our subsequent research.
[3] Li JH, Liu B, Hua W, Ma YS. Effects of intermolecular forces on deep sub-10 nm spaced sliders. IEEE Transactions on Magnetics. 2002, 38, 2141-2143.
Reviewer 4 Report
On looking at the paper in greater detail, I found that my physics/maths knowledge was insufficient to judge the soundness of the paper. The paper appears excellent.
Reference numbers in square brackets would make it more easily read. eg [1]
Author Response
Reviewer's Point: Reference numbers in square brackets would make it more easily read. eg [1].

Author's Response: Thank you very much for your kind suggestions. We have revised the format of reference numbers according to the journal guidelines.
Reviewer 5 Report
Overall I find this to be a well written article. The background section in thorough, the methodology and theory is laid out clearly, and the conclusions are supported by the evidence. There seem to be some issues with the formatting of the reference numbers, but I assume that will get fixed in copy editing.
Author Response
Reviewer's Point: There seem to be some issues with the formatting of the reference numbers, but I assume that will get fixed in copy editing.

Author's Response: Thank you very much for your kind suggestions. We have revised the formatting of reference numbers according to the journal guidelines.
