Adhesion, friction and wear characterization of skin and skin cream using atomic force microscope.

Skin cream is commonly used to improve skin health and create a smooth, soft, and moist perception by altering the surface roughness, friction, and adhesion of skin surface. In this study, a systematic characterization of the friction and adhesion properties of skin and skin cream was carried out, which is essential to develop better skin care products and advance biological, dermatology, and cosmetic science. Since cream rheology is expected to be a function of its thickness as well as the velocity and normal load during its application, friction and adhesion experiments were performed at a range of cream film thickness, velocity, and normal load in order to study their effect on virgin skin and cream treated skin. Since environmental dependence of skin and skin cream is of importance, the effect of relative humidity and temperature on the coefficient of friction and adhesive force was also studied. Durability of the virgin skin and cream treated skin was studied by repeated cycling tests. These experiments were performed by using an atomic force microscope (AFM) and a macroscale friction test apparatus in order to study the scale effects. Friction and wear mechanisms under various operating conditions are discussed.