Towards simultaneous measurements of skin friction and contact area: Results and experiences

Abstract

This article investigates one of the important parameters when designing for feel, namely the friction coefficient. An experiment was performed to evaluate how fringe projection could be used to investigate the topography of the fingertip, especially while in contact and sliding on a smooth surface. By allowing this smooth surface to be a small sheet of glass, a topographic camera could take pictures through it. The glass was also connected to a universal force gauge to measure normal and tangential forces from which the coefficient of friction could be calculated. The intention was to get dependable data on the forces, coefficient of friction, apparent contact area and actual contact area. This set-up was tested using 66 students who used one and three fingers in both dry and wet conditions and with a rubber glove. In order to measure natural everyday friction, they were not given any particular instructions on how to clean or slide their fingers. This method resulted in a much higher variation in friction coefficients than has been found in previous research. In particular, many higher values were noticed. This illustrates that the friction coefficient is a very hard parameter to rely on when it comes to designing surfaces for feel.