Will "Gecko Tape" Let Humans Climb Walls?

By John Roach
for National Geographic News
June 2, 2003

Humans may someday be able to scuttle up walls, scamper across ceilings, and scurry out windows with the agility of a startled gecko in the tropical night—thanks to a new adhesive tape that mimics the lizard's sticky feet.

"Geckoman is less than science fiction these days," said Andre Geim, a physicist at the University of Manchester, England, who is part of a team that overcame considerable engineering challenges to produce the first synthetic "gecko tape."

The breakthrough comes just a few years after scientists resolved the centuries-old mystery of how geckos climb up and down trees and cling from the underside of branches.

The geckos' secret is millions of microscopic hairs on the pads of their feet. Each hair, or seta, provides a miniscule adhesive force called van der Waals, which operate over very small distances but bond to just about anything.

Since geckos have millions of these hairs on each foot, their combined adhesive force is hundreds of times greater than what is required for the gecko to hang from a ceiling by one foot.

Inspired by this biological design, Geim and his colleagues etched a plastic mold with a scanning electron microscope that they used to make little hair-like pillars for a 0.4 inch by 0.4 inch (1 centimeter by 1 centimeter) piece of tape.

Once they make the tape more durable and scale up the technology, Geim and colleagues calculate that a human could hang from a ceiling by one tape-covered palm.

"I think it is really exciting to see every step toward the design of an adhesive that can be as effective as a gecko," said Robert Full, a biologist at the University of California at Berkeley. "It shows the importance of biological inspiration."

Full is part of the team that discovered in 2000 the adhesive force of the hairs on the pads of gecko feet. He and his colleagues are also developing synthetic setae based on the biological design of the gecko.

Machining Tape

To make tape stick like a gecko, Geim and his colleagues etched several molds to make various sized plastic pillars that resembled the hairs on gecko feet. "We tried to find out what would be optimal geometry," said Geim.

Through trial and error, the researchers found that no matter what the diameter of the pillar, the adhesive force created does not change.

Continued on Next Page >>




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