Get a grip: Truth about fingerprints revealed

Get a grip: Truth about fingerprints revealed
12 June 2009 by Ewen Callaway
The long-held notion that fingerprints marks help us grip more firmly appears to be wrong. Instead, a new study finds that the marks actually reduce the friction between skin and surfaces.
"Because there are all the gaps between the fingerprints, what they do is reduce the contact area with the surface," says Roland Ennos, a biomechanicist at the University of Manchester, UK, who led the study with colleague Peter Warman.
Rather than singe the prints off an unlucky student to compare hands with and without prints, Ennos rigged Warman's fingers to a special device that slides a weighted sheet of Perspex across a finger and measures the resulting frictional force.
Ennos and Warman determined that the amount of friction generated went up as more of the fingerprint was touching the sheet, but not by as much as expected. This indicated that the skin was behaving like rubber, where friction is proportional to the contact area between the two surfaces. With most solids, friction depends on the force of contact between of the surfaces.
Further tests with varying widths of plastic sheet confirmed this behaviour.
Measurements taken from ink marks then revealed that fingerprints actually reduce the area in contact with a surface by about one third, compared with smooth skin. Therefore fingerprints actually reduce friction, Ennis says.