Characterizing and imaging gross and real finger contacts under dynamic loading

We describe an instrument intended to study finger contacts
under tangential dynamic loading. This type of loading is relevant to the
natural conditions when touch is used to discriminate and identify the
properties of the surfaces of objects — it is also crucial during object
manipulation. The system comprises a high performance tribometer
able to accurately record in vivo the components of the interfacial
forces when a finger interacts with arbitrary surfaces which is combined
with a high-speed, high-definition imaging apparatus. Broadband skin
excitation reproducing the dynamic contact loads previously identified
can be effected while imaging the contact through a transparent window,
thus closely approximating the condition when the skin interacts with a
non-transparent surface during sliding. As a preliminary example of the
type of phenomenon that can be identified with this apparatus, we show
that traction in the range from 10 to 1000 Hz tends to decrease faster
with excitation frequency for dry fingers than for moist fingers.