No blemish stuck to it

Inspired by the sticky feet of the gecko, an adhesive tape capable of keeping dirt away from itself.

By: Ofir Marom

Geckos surpass adhesive tapes in a number of ways and one of the interesting ones is that even after repeated contact with dirt and dust, their legs stick perfectly to smooth surfaces. After many years of research, researchers were able to develop an adhesive tape that imitates the adhesive mechanism of the gecko's fingers, and just like them, it is also able to keep dirt away from it and maintain the ability to adhere many times.
Gecko feet are not coated with a sticky substance and they do not need to create a vacuum to stick to surfaces. Instead, each of their fingers is covered in millions of tiny hairs that create an electric quantum effect. A weak attraction is created between each hair and the surface as a result of the random movement of electrons (van der Waals forces). The sum of the forces between millions of hairs and the surface adds up to a significant force, which allows the gecko to maintain a firm grip even on polished glass. Dirt left on the gecko's legs impairs its ability to stick, so it must clean them continuously. The removal of dirt is carried out while moving, when the gecko drags its legs over part of the surface. As a result of the friction created, the large pieces of dirt are removed, while the small particles fall and settle between the hairs.

The new adhesive tape developed by a group of scientists from the USA and Germany works in exactly the same way. The film is a dry material that is covered with artificial and flexible microhairs similar in shape to a mushroom. To test the cleaning ability of the adhesive film, experiments were carried out with tiny glass beads of various sizes, which simulated dust grains. In the experiments it was found that when the diameter of a bead exceeded the diameter of the microhair, the material lost its stickiness after the first contact, but after a cleaning process similar to that used by the gecko, most of the dirt was removed, and the adhesive tape returned to almost 100% of its capacity. When the diameter of the bead was smaller than that of the microhair, only one-third of the original adhesion force was restored.
"In order to perfectly mimic the gecko's adhesion ability, we need to create nanometer-sized hairs that are smaller than most dirt particles," says Dr. Michael Röhrig. Using this type of adhesive tape will allow food packages or bandages to be opened and closed many times. There is no doubt that after the development is completed it will be possible to find many uses for the adhesive tape with such capabilities in the field of sports and medicine or in the automotive industry and space technology.

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