Sliding direction dependence of stick-slip in finger friction

The sliding direction dependence of finger stick-slip significantly affects tactile perception. In this study, a balance model and a viscoelastic model were established to quantitatively describe the mechanism of this di-rection dependence. Parameters affecting the occurrence of stick-slip were analyzed, including the damping ratio zeta, tangential stiffness k, and the difference between static and sliding force Delta Ff, etc. During experiments, the structure of phalanges caused larger Delta Ff in distal direction than in proximal. This effect, together with the smaller k, caused the stronger stick-slip phenomena, which agreed well with the models. These findings could enhance the understanding of principles and mechanism of finger stick-slip and might provide guidance in better describing and modeling the tactile perception.