With thanks from CSIRO Australia newsletter.
Watching geckos scurry up walls and over windows, you could be forgiven for thinking they have suction pads on their feet. You might even imagine they secrete some sort of special glue. In truth, they do it simply because they have hairy feet. Amazingly, engineers at the University of Berkeley in California have created an adhesive material which works in the same way.
Suction pads would be bad news for the poor gecko. Not only would they always have to press their feet hard into the wall to make them stick, they’d also need to tug hard to remove them. This would be exhausting work.
Instead, they have a large number of tiny, microscopic hairs, each with a split end, creating a large surface area for their foot-pads. The molecules at the tip of each split exert a very weak attracting force. On their own, each hair couldn’t hold very much, but all together they manage to stop the gecko from sliding down nearly any surface. Better yet, the hairs are easy to keep clean, and it takes very little effort for the lizard to lift its foot from the wall as it climbs.
Obviously it would be quite useful if we could produce something similar. Researchers have created a material from plastic fibres which are only 20 micrometers long and 0.6 micrometers wide (that’s 1/100th the width of one of your hairs!). These plastic fibres are packed together tightly into a small space and act like the gecko’s hairs – when sliding up against a surface, they adhere in a given direction. The molecular forces hold it in place and stop it from sliding backwards while still making it easy to move forwards. So far, the researchers have managed to hold up weights of up to 400 grams on a wall using only two centimetre wide squares of the material.
The next step is to attempt to make their material cling just as easily to rough surfaces and find a way to keep the hairs free from dirt and dust. They see this new type of adhesive being useful in a number of markets, including making climbing robots. I think I should ask them to design me a pair of super gecko-powered cricket gloves!