Reusable and self-cleaning tape is inspired by gecko feet

Gecko feet have the same ability to stick as a piece of tape. However, there is one difference: the gecko leg always maintains the ability to stick no matter how many times it is used.

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Now, thanks to a study conducted by Carnegie Mellon University and the Karlsruhe Institute of Technology in Germany, in the future we will be able to use a reusable tape with multiple self-cleaning abilities. from the gecko.

The reason for the gecko foot has good adhesion ability to help it climb to the vertical surface is thanks to millions of microscopic hard hairs. These hairs bind temporarily to the surface at the molecular level thanks to Van der Waals interaction laws (causing gravitation and repulsion at the molecular level). When a gecko crawls forward, friction creates when the feet push back behind the surface, causing a large amount of dirt particles to fall off the hard hairs and smaller particles fall to the folds. in the foot skin. This is an important factor in the self-cleaning ability of gecko feet.

Scientists have copied this effect by creating a sticky tape with microscopic plastic hairs with mushroom shapes in 3 dimensions. Next, they spread small glass balls instead of dust onto a plate. A piece of tape attached to the hard mushroom-shaped hairs pressed against the disk filled with glass bridges, then they slid the tape several times and removed it, similar to how geckos lift their feet on the wall.

In the case of hard hairs having a diameter smaller than the diameter of the sphere, the initial adhesive tape will lose its grip after the first contact with the disc surface. However, it quickly regains the grip force from 80 to 100% equivalent to 8 to 10 times of continuous removal. This is the self-cleaning effect of a piece of tape adhered to by this action, causing the spheres to fall out of the microscopic hair.

However, when the hairs are larger in diameter, the spheres tend to fall into the gap between the fibers instead of falling out. Since there are no folds on the bandage like the gecko's skin, the self-cleaning effect is not promoted. Only 1/3 of the initial adhesion force is recovered after the test is performed.

Therefore, scientists believe that smaller hard hairs will have a better self-cleaning effect. With nanometer sizes, they will be small in diameter of dust particles. The team has now reproduced the same folds of gecko skin on a piece of adhesive tape so they can hold larger dust particles. They also planned to test an improved version of the tape with real dirt in the future. Hopefully once it becomes more perfect, the technology can be used in applications such as "reusable adhesive tape, self-cleaning clothes and medical adhesive tape".

This is not the first time that the unique adhesion ability of gecko feet is an idea for a study of materials. In the past, Amherst University of Massachusetts and Kiel University have also made super-sticky materials based on the mechanism of gecko feet.

A detailed article on the study has just been published in Interface magazine.