Gecko Feet—Best Foot Forward: Design in Nature by Melinda Christian

Mankind may walk on the moon, but we still can’t catch the gecko. Climbing up walls and walking across ceilings—the stuff of science fiction for humans—is just a part of the gecko’s daily routine. And scientists are eager to imitate his secrets.

Scientists have long tried to understand how geckos can walk on walls and ceilings, even on smooth glass. How can a dry foot stick on glass without sticky glue or suction cups? It wasn’t until the twenty-first century that the gecko’s secret was finally discovered. Now researchers are hoping to apply these discoveries to robots.

The ridged toes of many species of gecko are covered with millions of tiny hairs called setae, and at the end of each hair is a bundle of tiny strands called spatulae. These strands, much smaller than a human hair, are so tiny that individual molecules on the gecko feet are attracted to the individual molecules on the surface of the glass.

This molecular attraction is called van der Waals forces. Simply put, if the electrons of two different molecules are thrown out of sync in close contact to each other, they form a temporary bond.

In the gecko’s case, the bond is also directional, meaning that it sticks in only one direction. That’s key. The gecko can release the bond simply by lifting its foot in a different direction. No “unsticking” necessary. (Think of loosening the hook fastener on a pair of dress slacks. The fastener is not glued down, so it doesn’t have to be yanked apart. You simply lift it forward.)

So far, scientists have developed “gecko tape,” a dry unidirectional adhesive, based on the gecko’s remarkable “toe fuzz.” When you pull the tape one direction, it sticks; but when you pull it another direction, it releases.

But the mechanics of climbing are complex and more challenging to emulate. Still, researchers at Stanford’s Center for Design Research are working on it. First they made synthetic setae out of a rubber-like material. Then they put this material onto a lizard-like robot they called Stickybot. Not to be outdone, Carnegie Mellon University has developed another robot called the Geckobot.

Though this nanotechnology is still in the early stages of development, who knows what the future holds? A fully functioning gecko-footed robot would be of immense value in reaching places too difficult or dangerous for humans.

Thanks to God’s amazing design of gecko feet, we could one day live in a world where tires grip smooth surfaces, climbing gloves and boots grip rocks, and even Spider-Man suits are a reality (seriously, the Center for Design Research is working on a Z-Man suit). But the gecko, with its fantastic ability to scamper up glass walls and ceilings, still wins by a foot.