  In humans, the tactile perception of fine textures is mediated by skin
vibrations when scanning the surface with the fingertip. These vibrations are
encoded by specific mechanoreceptors, Pacinian corpuscules (PCs), located about
2 mm below the skin surface. In a recent article, we performed experiments
using a biomimetic sensor which suggest that fingerprints (epidermal ridges)
may play an important role in shaping the subcutaneous stress vibrations in a
way which facilitates their processing by the PC channel. Here we further test
this hypothesis by directly recording the modulations of the
fingerpad/substrate friction force induced by scanning an actual fingertip
across a textured surface. When the fingerprints are oriented perpendicular to
the scanning direction, the spectrum of these modulations shows a pronounced
maximum around the frequency v/lambda, where v is the scanning velocity and
lambda the fingerprints period. This simple biomechanical result confirms the
relevance of our previous finding for human touch.
