Abstract
When we touch an object, complex frictional forces are produced, aiding us in perceiving surface features that help to identify the object at hand, and also facilitating grasping and manipulation. However, even during controlled tactile exploration, sliding friction forces fluctuate greatly, and it is unclear how they relate to the surface topography or mechanics of contact with the finger. We investigated the sliding contact between the finger and different relief surfaces, using high-speed video and force measurements. Informed by these experiments, we developed a friction force model that accounts for surface shape and contact mechanical effects, and is able to predict sliding friction forces for different surfaces and exploration speeds. We also observed that local regions of disconnection between the finger and surface develop near high relief features, due to the stiffness of the finger tissues. Every tested surface had regions that were never contacted by the finger; we refer to these as “tactile blind spots”. The results elucidate friction force production during tactile exploration, may aid efforts to connect sensory and motor function of the hand to properties of touched objects, and provide crucial knowledge to inform the rendering of realistic experiences of touch contact in virtual reality.
Highlights
The tools we touch, grasp and manipulate often have topographical features such as ridges, bumps and texture that are meant to guide our gestures and provide crucial information on their nature and function
To clarify the relation between contact geometry and force production during tactile exploration of relief surfaces, we developed a simplified analytical model that could be used for comparison with our measurements
We investigated the frictional sliding of the fingertip against relief surfaces, using high-speed video and force measurements, and analyzed the results with the aid of a friction force model that accounted for interfacial and deformation effects
Summary
The tools we touch, grasp and manipulate often have topographical features such as ridges, bumps and texture that are meant to guide our gestures and provide crucial information on their nature and function. While the relevance of friction forces to sensory and motor functions of the hand is well established, our understanding of how time-varying friction forces are produced during contact with non-flat surfaces is incomplete This can partly be attributed to the complex dynamics governing the tribology of the finger pad[12], including the moisture content of the fingertip skin, which can affect the mechanics and dynamics of frictional sliding sliding[12,13,14], static to sliding transitions[15,16,17], and the presence of non-Coulombic behavior[18]. The evolving regions of contact are difficult to capture during tactile exploration, and there has been little prior empirical investigation of the role of contact geometry in shaping forces felt by the finger
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
