In addition to helping us grip, the ridges on the skin of our fingertips help us feel fine textures and tiny objects on a surface, French researchers report in the Jan. 30 issue of Science. Previous studies have shown that this ability to feel fine features – less than 200 micrometers, or roughly the width of a human hair – involves skin vibrations that arise as our finger scans a surface. To investigate how these vibrations translate into an actual feeling, Julien Schiebert and colleagues developed a mechanical sensor covered with a stretchy elastic cap that can be either smooth or ridged the way our fingertips are. When the “fingerprinted” sensor was rubbed across a variety of patterned surfaces, the vibrations that developed had a frequency that certain nerve endings in the skin, called “Pacinian corpuscles” are able to detect. The corpuscles are connected to sensory neurons that signal the brain once activated. (Pacinian corpuscles are known to be involved in sensing fine textures. A separate type of nerve ending is involved in sensing coarser textures.) The fingerprinted surface – but not the smooth one -- appeared to amplify and filter certain vibrational frequencies, enabling the nervous system to detect the signal, the researchers report.
Article #24: "The role of fingerprints in the coding of tactile information probed with a biomimetic sensor," by J. Scheibert; S. Leurent; A. Prevost; G. Debregeas at Laboratoire de Physique Statistique de l'ENS, CNRS-ENS-Universite Paris 6 & Paris 7 in Paris, France.