A team of engineers has formulated a new method of adhesion based on a natural phenomena found in geckos. Inspired by the gecko’s ability to stick to any kind of surface and easily un-stick itself, the engineers from Northwestern University and the University of Illinois have developed a new reversible adhesion stamp. The team created a square polymer stamp that can easily transport an array of electronic devices and print them onto a diverse range of complex surfaces including clothing, plastics and leather.
The footpad of a gecko contains micro- and nano-filaments which allow the lizard to increase or decrease its contact area with a surface. Thus the secret to the square polymer stamp is the design of its underside surface, which incorporates four pyramid-shaped rubber tips, one in each corner. These are designed to mimic a gecko’s foot, whereby the amount of contact made from the flexible surface of the stamp to the surface of an electronic device can be altered.
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When the four pyramids on the stamp press firmly against the surface of an electronic device, the soft tips expand and thus increase the surface-to-surface contact. The stamp can pick up the device and then by returning to its original pyramid shape (removing the adhesive force) the electronic device can be easily transferred to another surface.
“[The] design of the pyramid tips is very important,” said Yonggang Huang, Professor of Civil and Environmental Engineering and Mechanical Engineering at Northwestern University. “The tips have to be the right height. If the tips are too large, they can’t pick up the target, and if the tips are too small, they won’t bounce back to their shape.”
After conducting many tests using the stamp and electronics, the engineers concluded that the stamp could vary its adhesion strength by 1,000 times. They were also successful at printing layers of electronics, that may lead to the development of complex devices in the future.
The research was published in Proceedings of the National Academy of Sciences (PNAS).
The gecko’s remarkable climbing ability was also recently explored by another group of U.S. engineers, who created the Stickybot, a robot that can climb up rough surfaces such as brick walls or concrete.