Experimental approach of contact mechanics for polyethylene materials with human skin under wet condition

Abstract

As a lifestyle habit, shoppers like to lick their fingers before opening the polyethylene (PE) shopping bag. In fact, this implies a scientific problem, that is, moisture has an impact on the friction behavior between the plastic bag and the surface of the finger skin. In this study, an experimental method was employed to measure skin friction at three different hydration levels. The high-density polyethylene (HDPE) and low-density polyethylene (LDPE) materials were performed, and photographs of fingertips touching PE films were recorded by a camera. The experimental results showed that the applied normal load is positively correlated with the friction force and negatively correlated with the friction coefficient. And moisture content will increase friction. Specifically, when the fingertip slides on the HDPE film, the friction coefficient of the water-soaked skin is 5.9 times that of the dry skin. It can be inferred that the decrease in modulus of elasticity, as well as volume expansion, leads to an increase in contact area when the skin is wetted with water. This is the main reason for the increase in finger friction. In addition, a negative power function model was established to describe the relationship between the coefficient and the friction conditions by considering the combined effects of hydration level, normal load and material.

Abbreviations: CCD: Charge-coupled Device; COF: Coefficient of friction; HbA1C: Hemoglobin A1C; HDPE: High-density polyethylene; LDPE: Low-density polyethylene; PE: Polyethylene; SC: Stratum corneum;

Keywords:

• Skin friction
• sliding behavior
• hydration level
• polyethylene plastic bag

Authors’ contributions

Chunge Wang and Sheng Zhang conceived the subject of the review. Chunge Wang and Bangbang Ma wrote the manuscript and contributed equally to the content. Chunge Wang and Sheng Zhang edited and reviewed the paper before submission. All authors participated in the discussion of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data needed to evaluate the conclusions in the paper are presented in the paper.

Additional information

Funding

Ningbo Scientific and Technological Innovation 2025 Major Project [No. 2021Z108].