Are the fingertips of physics enough for the NEET

Fingerprints: More grip thanks to finger sweat

Apart from primates, only koalas in the animal kingdom have the characteristic grooved pattern on their fingertips. It can therefore be assumed that fingerprints give tree climbers more holding power. But how they fulfill this function is the subject of controversial debate among researchers. Gun-Sik Park from the National University in Seoul and colleagues have now investigated how our hands use the interaction of fingerprints and finger sweat to maximize the frictional forces on a smooth surface.

As you write in the specialist magazine »PNAS«, the suspicion arises that sweat plays a special role. Because our fingertips are covered with sweat glands, which also react less to body temperature than to the emotional state of the owner. Stress leads to moistening of the fingertips - perhaps to enable a faster escape into the treetop.

However, the fingers should not get too wet either, otherwise there is a risk of excessive water loss and the risk of slippery hands slipping off again. With the help of imaging processes, the team has now found that the body finely regulates the moisture on the skin of the fingertips. When test subjects touched a glass surface with initially dry fingers, their sweat glands began to produce secretion. At a certain point, however, the grooves of the fingerprints softened to such an extent that they mechanically closed the glands. If, on the other hand, the test subjects tended to have sweaty fingers at the beginning, the grooves ensured that the superfluous substance was removed. In the end, the moisture on the fingertip leveled off at the same value - at which the friction between hand and surface is optimal.