Tribological Measurements of Human Skin

There are practical answers to tribology-related problems all around us. Often, one of the interacting surfaces in relative motion is the human skin. Tribological measurement of the skin is an asset to study the properties of the skin and how they are altered in different conditions and with the popular dermal treatments. Test procedures for skin tribology must be in vivo, subject- and anatomical location-specific. In this system, measurement includes the contact with a flexible body and the presence of friction-induced vibration. Tribological studies depend on the frictional and electrical properties of the skin surface, which are determined by the frictional coefficients. These studies are used to quantify skin hydration and health. The friction coefficient of the skin measured depends on key factors like age, anatomical site, and skin hydration. Other factors which affect the coefficient are the design of the measuring instrument and the probe geometry and material. It was found that the skin with decreased hydration had a reduced friction coefficient and an increased resistance to current flow. The treatments on the skin which can affect the skin hydration level also influence the friction coefficient. The application of emollients and moisturisers influences the quantity of greasiness and stickiness quantitatively. Surface texturing and polymer brush coatings are intriguing new developments because they offer a way to customise friction in sliding contacts without having to make significant product adjustments.