Fingerprints don’t increase friction to improve grip on smooth surfaces

June 13th, 2009 - 11:34 am ICT by ANI  

Washington, June 13 (ANI): A new study has debunked the age-old belief that fingerprints provide friction to improve people’s grasp on smooth surfaces.

Roland Ennos, who led the study at the University of Manchester, recruited Manchester undergraduate Peter Warman to test out fingerprint friction by pushing a piece of acrylic glass against the latter’s finger.

A research article published in the Journal of Experimental Biology reveals that the researchers designed a system that could produce forces ranging from a gentle touch to a tight grip, and then Warman strapped his index finger into the machine to begin measuring his fingerprint’s friction.

However, after days of testing, the researcher observed that the friction did not increase in proportion to the amount the glass pushed against Warman’s fingers and thumbs.

Ennos said that the friction increased by a smaller fraction than had been expected.

The researchers realised that rather than behaving like a normal solid, the skin was behaving like rubber, where the friction is proportional to the contact area between the two surfaces.

The study group then set out to determine whether the skin behaves more like rubber than a normal solid.

Varying the area of each fingerpad that came into contact with the surface by dragging narrow and wide strips of the glass along Warman’s fingerpads, the researchers did find the friction to increase as more of the fingerprint came in contact with the surface, so the skin was behaving just like rubber.

Finally, the friction issue was clinched when Warman measured his fingerprints’ surface area. The area of skin in contact with the glass was always 33 per cent less than if the fingerpads were smooth resulting in the maximum contact area.

Fingerprints definitely don’t improve a grip’s friction because they reduce our skin’s contact with objects that we hold, and even seem to loosen our grip in some circumstances.

Ennos said that the observations made during the study suggested that the idea that our fingerprints provide friction for grip is just another urban myth.

According to the researcher, our fingerprints may function in other ways. They might have evolved to grip onto rough surfaces, like tree bark; the ridges may allow our skin to stretch and deform more easily, protecting it from damage; or they may allow water trapped between our finger pads and the surface to drain away and improve surface contact in wet conditions.

Other researchers have suggested that the ridges could increase our fingerpads’ touch sensitivity. (ANI)

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