Friction Behavior of Fingers on Micro-Textured Flexible Surfaces

Abstract

Compared to rigid materials, people have a distinct tactile perception when touching flexible materials. Moreover, adding micro-patterns to the surface enhances the tactile experience even further. This sensation arises from the physical stimulation of frictional behavior between the skin and flexible materials. Therefore, this study focuses on human fingers as the research subjects and employs flexible materials with micro-textured surfaces as the frictional objects. A friction test setup is designed to conduct a series of finger friction experiments, and theoretical explanations are provided to elucidate the reasons for performance variations. Research findings show that as the normal load increases, the frictional force gradually increases, while the friction coefficient decreases. The former is attributed to the expanding contact area, while the latter is due to the inconsistent rate of frictional force increment with the normal load. The impact of friction velocity is mainly caused by changes in the viscous forces generated at the liquid film in the contact interface and the energy loss in elastic hysteresis. On the other hand, the effect of surface micro-topography is primarily a result of the transition between partial contact and full contact modes under the influence of normal load, leading to alterations in the contact area. Overall, during the finger-friction process on a flexible micro-textured surface, changes in contact area play a vital role in modifying frictional performance, with adhesive friction exerting a more significant influence than deformation friction. This study summarizes the variations in frictional performance parameters based on experiments and analyzes the effects of contact area changes and deformation friction mechanisms from a theoretical perspective, providing a theoretical foundation for exploring the genesis of delicate tactile sensations during friction.