The gecko is getting a lot of exposure in insurance commercials on TV, but that’s not why the lizard has stimulated scientists’ imaginations. Researchers are paying heed because geckoes and other lizards and insects can run up, down or sideways on nearly any surface, wall or ceiling, without falling off. Their remarkable ability has inspired studies of new forms of adhesives.
“The secret to the lizards’ mobility is the millions of micron-scale fibrils on each toe that form a self-cleaning dry adhesive,” says Anand Jagota, professor of chemical engineering and director of the Bioengineering Program. “Each fibril consists of up to 1,000 spatulae, or flattened tips, that are only tens of nanometers in thickness. These nanostructures hold the promise of an entirely new type of adhesive.”
The study of gecko-inspired adhesives is one of the latest examples of biomimetics, or the development of technology that mimics nature. Velcro was developed when a scientist noticed plant burrs stuck in the fur of his dog. A tropical sea sponge might inspire new fiber-optic strands, and a sea creature related to the starfish could light the way to a better design for optical lenses.
With funding from NSF and the U.S. Department of Energy, Jagota is conducting experiments to measure the gecko’s adhesion and friction while also seeking to fabricate gecko-like adhesives using polymers. His group includes Chung-Yuen Hui, professor of theoretical and applied mechanics at Cornell University; Richard Vinci, professor of materials science and engineering at Lehigh; Manoj Chaudhury, professor of chemical engineering at Lehigh; and Nicholas Glassmaker of DuPont, as well as graduate and undergraduate students at Lehigh and Cornell.
“The idea is to develop the architecture of these kinds of adhesives so that they can be made from a variety of materials,” Jagota says. His group has developed one design that Jagota calls a “mini-Parthenon,” because its fibrils form columns and a roof block. That design, Jagota notes, is much stickier than a plain block of the material.
“By changing structure and adding two critical elements from nature – the fibril and the terminal thin film – we have improved performance eight or nine times over the performance of the design using plain material,” says Jagota. “We think this phenomenon has to do with the thinness and smallness of the feet, and that is part of what we’re measuring.”
Bio-inspired adhesives might be more useful in applications requiring repeated adhesion than in those imposing heavy loads, says Jagota. “There is a lot of potential here and we’re excited to try to demonstrate it.”