University of California scientists have developed an adhesive that, they claim, is the first to reproduce the quick catch and rapid release traits of a gecko's foot. The research team says that the material may find its application in a wide range of products, ranging from climbing equipment to medical devices. The new material has been crafted from millions of tiny, hard, plastic fibres that establish grip.
According to the researchers, a mere square two centimetres on a side can support 400 grams (close to a pound) of weight. Unlike tape that sticks when it is pressed onto a surface, the new adhesive sticks as it slides on a surface, and releases as it lifts.
The researchers say that this is the trick behind a gecko's speedy vertical escapes, and something very important for any application that requires movement such as climbing. "The gecko has a very sophisticated hierarchical structure of compliant toes, microfibers, nanofibers and nanoattachment plates that allows the foot to attach and release with very little effort," said Berkeley professor Ron Fearing, co-author of the study published online in the Journal of the Royal Society Interface.
"The gecko makes it look simple, but the animal needs to control the directions it is moving its toes--correct movement equates to little effort," he added. Experiments have shown that the new material is also novel in that it gets stronger with use. It tightens its hold as it is rubbed repeatedly against a glass plate.
The researchers have revealed that the extra strength is caused by the fibres bending over to make more contact, yet once released, the fibres return to their original shape. They are exploring ways to permanently bend the fibres in order to achieve strong grip from the outset, and to avoid massaging for the purpose.
According to Fearing, the new material is the first to mimic the nature of the gecko's characteristic "non-sticky by default" feet. The Berkeley researchers, all engineers, have worked closely with biologists Robert Full, also at Berkeley, and Kellar Autumn of Lewis and Clark College in Portland, Ore., to uncover the key natural properties behind that unique foot, the secret to high mobility on sheer surfaces. Fearing and his colleagues are part of an NSF-supported Nanoscale Interdisciplinary Research Team (NIRT) that was specifically tasked in 2003 with developing biologically-inspired synthetic gecko adhesives.
"The results of this project are an impressive example of how teaming engineers with biologists results in a better understanding of the role of 'engineering' in nature," says National Science Foundation (NSF) officer Lynn Preston. "This is a perfect example of how to turn that understanding into products that are as sophisticated as those developed by 'Mother Nature'," she added.