Geckos inspire robots, but there’s no reason to limit one’s imagination. Why not use the fantastic properties of gecko feet to make something everyone needs: tape?
At the University of Kiel in Germany, a group led by Stanislav Gorb has made a silicone tape patterned after the feet of the lizard. Unike your garden-variety scotch tape, this stuff is strong, it can be used over and over again, and it doesn't leave sticky goo behind. In fact it is so strong a piece a bit less than 8 inches by 8 inches (20 cm on a side) can hold up the weight of a fully grown person.
How does this work? Geckos and some insects have tiny hair-like structures on their feet called setae, and each one end in a flat structure called a spatula. When they touch a surface, the attraction between molecules, known as the Van der Waals forces, pull on them and cause them to stick. This is the same force that makes water droplets stick to the ceiling or to the side of a glass.
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Ordinarily Van der Waals forces are relatively weak (this is why water droplets stuck to a surface never get very big). But when hundreds of thousands of spatulae on a gecko’s foot are working together they can hold a lot of weight (which is why geckos can curry across a ceiling and up a glass window).
Ordinarily Van der Waals forces are relatively weak (this is why water droplets stuck to a surface never get very big). But when hundreds of thousands of spatulae on a gecko’s foot are working together they can hold a lot of weight (which is why geckos can curry across a ceiling and up a glass window).
The tough part about building this kind of material has always been fabricating it, and getting it to work on a surface even if it isn’t perfectly smooth. Gecko’s setae are flexible, enough so that they can mold to the surface they are on. Finding artificial materials that can do that also has been tougher, and fabricating tiny hairs tougher still.
The team presented their work at the AVS Symposium in Nashville last week.
Image: University of Kiel, Germany
