Fingerprints enhance the sense of touch

London, Jan 30 (ANI): French scientists have found that fingerprints can actually help detect fine texture of surfaces and amplified vibrations identified by nerves deep under the skin.

Led by Georges Debregeas at the Ecole Normale Superieure in Paris, the research team rubbed an artificial fingertip across rough surfaces, and found that the tiny ridges on our fingers help us to grip objects by increasing friction.

They discovered that the ridges also amplify vibrations triggered when fingertips brush across an uneven surface, helping transmit the signals to deeply embedded nerves involved in fine texture perception.

For the study, the physicists covered a pressure-detecting sensor, acting as a nerve fibre, with an elastic material that was either smooth, or patterned with fingerprint-like ridges.

They then moved the 'fingertip' over a glass slide that had been covered with raised lines of uneven spacing and thickness, which made the artificial skin to vibrate at varying frequencies that could be detected by the sensor.

Mark Hollins a psychologist at the University of North Carolina at Chapel Hill said that using an artificial device to determine the role of fingerprints is "very novel".

In their studies on real fingertips, they had shown that humans feel fine textures by moving their fingers over a surface and triggering vibrations in the skin, which are picked up by nerves.

However, some of the nerve endings, called Pacinian corpuscles, are relatively deep - about 2 millimetres - under the skin, raising questions about how they could detect such subtle vibrations.

And it was found that certain vibrations from the patterned fingertip are 100 times stronger than those from the smooth fingertip.

According to the results, the ridged skin acts as a filter that selects which vibrations to transmit to the underlying nerves.

For a typical human fingertip with ridges half a millimetre apart and which scans a surface at 10-15 centimetres per second, the amplified frequencies would be about 200-300 hertz, the team calculated.

The frequency range is significant because the embedded Pacinian nerve fibres are most sensitive to vibrations at 250 hertz.

"Fingerprints might actually improve the sensitivity of perception by enhancing the skin vibrations at a frequency that matches the best frequency of these Pacinian corpuscles," Nature magazine quoted Debregeas as saying.

Making use of the findings, engineers could now hope to design robots with a more refined sense of touch, said Richard Crowder, a robotics engineer at the University of Southampton, UK. (ANI)