A study suggests how fingerprints enhance grip. Why fingerprints evolved in primates and the role of fingerprints in aiding grip are not fully understood. The tips of fingers and toes have a much greater density of sweat glands than flat skin, and the sweat glands under fingerprint ridges respond to emotional states and anxiety rather than temperature changes, suggesting that the fingerprint ridges interact with moisture to regulate friction between the skin and the gripped surface. Gun-Sik Park, Michael J. Adams, and colleagues used various spectroscopic and tomographic imaging techniques to characterize the behavior of moisture on a fingertip in contact with a glass surface. For an initially dry fingertip, sweat secretion led to plasticization of the skin and increased friction, until sufficiently close contact between the fingerprint ridges and the surface effectively blocked the sweat glands. For an initially wet fingertip, the fingerprint furrows facilitated the removal of excess moisture via capillary evaporation. Thus, regardless of whether the fingertip was initially wet or dry, the amount of moisture on the fingertip always ended up at the same value, which corresponded to the maximum friction between the finger and the glass. The results could aid in the development of improved tactile sensors and haptic feedback systems, according to the authors.
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Article #20-01055: "Fingerprint ridges allow primates to regulate grip," by Seoung-Mok Yum, In-Keun Baek et al.
MEDIA CONTACT: Gun-Sik Park, Seoul National University, REPUBLIC OF KOREA; tel: +82-10-5408-7749; e-mail: < gunsik@snu.ac.kr >; Michael J. Adams, University of Birmingham, UNITED KINGDOM; e-mail: < m.j.adams@bham.ac.uk >
Proceedings of the National Academy of Sciences