Fingerprint ridges allow primates to regulate grip

Seoung Mok Yum, In Keun Baek, Dongpyo Hong, Juhan Kim, Kyunghoon Jung, Seontae Kim, Kihoon Eom, Jeongmin Jang, Seonmyeong Kim, Matlabjon Sattorov, Min Geol Lee, Sungwan Kim, Michael J. Adams, Gun Sik Park

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Fingerprints are unique to primates and koalas but what advantages do these features of our hands and feet provide us compared with the smooth pads of carnivorans, e.g., feline or ursine species? It has been argued that the epidermal ridges on finger pads decrease friction when in contact with smooth surfaces, promote interlocking with rough surfaces, channel excess water, prevent blistering, and enhance tactile sensitivity. Here, we found that they were at the origin of a moisture-regulating mechanism, which ensures an optimal hydration of the keratin layer of the skin for maximizing the friction and reducing the probability of catastrophic slip due to the hydrodynamic formation of a fluid layer. When in contact with impermeable surfaces, the occlusion of the sweat from the pores in the ridges promotes plasticization of the skin, dramatically increasing friction. Occlusion and external moisture could cause an excess of water that would defeat the natural hydration balance. However, we have demonstrated using femtosecond laser-based polarization-tunable terahertz wave spectroscopic imaging and infrared optical coherence tomography that the moisture regulation may be explained by a combination of a microfluidic capillary evaporation mechanism and a sweat pore blocking mechanism. This results in maintaining an optimal amount of moisture in the furrows that maximizes the friction irrespective of whether a finger pad is initially wet or dry. Thus, abundant low-flow sweat glands and epidermal furrows have provided primates with the evolutionary advantage in dry and wet conditions of manipulative and locomotive abilities not available to other animals.

Original languageEnglish
Pages (from-to)31665-31673
Number of pages9
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number50
DOIs
Publication statusPublished - 2020 Dec 15

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. This work was funded by the National Research Foundation of Korea through the Korea government Ministry of Science and Information Communication and Telecommunication (MSIT) under Grants 2016R1A3B1908336 and 2018M3A7B4070990.

Publisher Copyright:
© 2020 National Academy of Sciences. All rights reserved.

All Science Journal Classification (ASJC) codes

  • General

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