Effect of Finger Sliding Direction on Tactile Perception, Friction and Dynamics

Human beings use certain styles when perceiving physical characteristics of objects with fingers. Sliding direction of finger contact is among the aforementioned styles. Thus, understanding the effect of sliding direction on tactile perception is essential. This study investigated the perception and identification of the roughness of sandpapers in two different sliding directions: proximal and distal. Furthermore, the corresponding tribological and dynamical properties of finger contact were examined using a custom setup. It was observed that the sliding direction and sliding speed influenced subjective judgment. The interaction between these two factors was also considered. A macroscopically continuous movement with a series of local collisions among the contact asperities enhanced the tactile perception in the proximal sliding. While in the distal direction, stick–slip occurred and interrupted the collision process, and reduced the tactile perception. The stick–slip phenomenon is modulated by various factors, including the external force and variations in the skin stiffness, which is influenced by the fingernail as well as the different friction properties in the two sliding directions.