Climbing a glass building? Try a gecko’s sticky pads

An irresistible attraction to gecko feet is an occupational hazard for engineers who study how one thing sticks to another. Geckos can climb just about anything, including glass, and in 2002 scientists identified the force of molecular attraction that bonds dry gecko footpads to a surface.

Engineers copied nature’s invention with synthetic gecko-inspired materials, but the artificial materials didn’t work well with heavy loads like the roughly 150-pound body weight of Elliot W. Hawkes, a Stanford graduate student in mechanical engineering.

He was part of a team that developed a climbing rig outfitted with gecko-inspired sticky pads. And he stars in a video demonstrating their accomplishment by ascending a short distance up a vertical glass surface.

He readily acknowledges that he looks nothing like Spider-Man. “The whole idea of a Spider-Man suit just ignores ergonomics,” he said. “We don’t have the upper body strength that a gecko has.”

In the rig the group developed, the pads on Hawkes’ hands are made of a number of small patches of an existing synthetic material based on gecko feet. Cables run from the pads to foot platforms so that his body weight is on his legs and he is leaning forward.

But what made the rig work, say the researchers, is the way they attached many small patches of adhesive material to the full hand pad, using degressive springs, which evenly distribute the weight of a human climber so that every small adhesive patch carries an even part of the load.

The research arm of the Defense Department created a functioning climbing rig a couple of years ago, the Stanford team said, but did not publish all the details of how it was done.

The Stanford team, which included Eric V. Eason and David L. Christensen, graduate students, and Mark R. Cutkosky, a professor of mechanical engineering, reported their work Nov. 19 in The Journal of the Royal Society Interface.