Finger pad mechanics during dexterous object manipulation

Humans are able to manipulate small objects with high dexterity. To achieve this, the central nervous system (CNS)critically relies on tactile information coming from the numerous mechanoreceptors innervating the hand. Finger pad mechanics has been extensively studied in passive touch conditions, revealing that slips at the fingertip-object contact occur progressively, starting at the periphery of the contact and propagating towards its center until full slip. The systematic occurrence of this partial slip phenomenon under tangential loading of the fingertip combined with the importance of cutaneous feedback in object manipulation led us to formulate the hypothesis that the CNS might rely on these partial slips to adjust the grip force exerted on the object. It is unclear, however, what is the level of partial slip at the fingertip-object contact during active object manipulation. To answer this question, we designed a manipulandum equipped with both fingertip force sensing and fingerprint imaging capabilities. Here, we describe the apparatus and lay out the experimental tasks that we will perform to assess the level of partial slip during dexterous object manipulation