Measurement of in-vivo friction coefficients of human skin by using multi-components load-cell

The friction coefficients have been used to evaluate skin care and cosmetic products which aim at conferring smoothness to skin. Cosmetic products are thought to perform their function by depositing sufficient amounts of desirable ingredients leading to perceptible change in adhesion and friction coefficients. We design the friction coefficients measurement system which is assembled with multi-component load cell and linear motor. The multi-component load cell simultaneously measures the normal load (Fz), and the friction forces (Fx, Fy) with strain gages while probe is sliced on the cosmetic applied skin of arm fixed with the linear motor. Capacity and accuracy of load cell are less than 5 N and 0.1%. In-vivo friction coefficients of skin of arm is varied from 0.177 to 1.327 dependent on the cosmetic products, normal load, materials and surface condition of probe.