Fig. 4.

(A) The finite-difference model of the fingertip. (B and C) Surface-deformation profiles when in contact with a low-friction (B) and a high-friction (C) surface for 1, 2, and 3 N. Point trajectories are shown in red. The black arrows represent the pressure and traction exerted by each point when brought in contact with the surface. (D) Total divergence of the contacted skin as a function of the normal force for friction coefficients varying from 0.1 to 0.6. (E) Stress profiles at 3 N of normal force for a high- and a low-friction condition.