There is a recent New York Times article which describes the difficulties of creating a robot with a sense of touch comparable to a human. One of the links in the article, “Feeling Small: Exploring the Tactile Perception Limits”, contains suprising results. It turns out our fingers are exponentially more sensitive than previous research has indicated. Earlier studies used abrasive paper, while this study used wave-like ridges, which may account for some of the difference in the new findings.
Human fingers, when using “dynamic touch” — sliding across a surface — can distinguish a ridge that is 13 nanometers, which is .013 microns, or about .0000005 of an inch. For comparison, the thickness of a sheet of standard copy paper is a mountainous .004 of an inch thick. The average particle size of green chromium oxide stropping compound is .5 micron, which produces a mirror finish on steel.
My mind is blown. Should I be able to feel the individual fibers on a Japanese tissue paper repair? Will I ever be able to pare leather smoothly enough?
Peachey Conservation 