Place a single water droplet on the sole of a gecko toe, and the pad repels the water. The anti-wetting property helps explain how geckos maneuver in rainy tropical conditions. However, saturate that same toe pad in water or drench the surface on which it climbs, and adhesion slips away, the researchers say.
As researcher Alyssa Stark research team leader explains, geckos do not fall from trees during downpours in the tropics. What, then, makes them stick? The team hopes to make that discovery in order to create synthetic materials that hold their grip in wet environments, such as inside the body, for surgical procedures.
“We are gathering many clues about how geckos interact with wet surfaces and this gives us ideas of how to design adhesives that work under water,” says Ali Dhinojwala, UA department of polymer science. “Nature gives us a certain set of rules that point us in the right direction. They help us understand limitations and how to manipulate materials.”
Stark and her research team members tested gecko toe hair adhesion in a series of scenarios: dry toe pads on dry, misted and wet surfaces and soaked toe pads on dry, misted and wet glass. The soaked toe pads demonstrated low to no adhesion proportionately with the wetness of the surface on which they were applied and pulled. Likewise, dry toe pads lost their adhesive grip increasingly with the amount of water applied to the surface upon which they were pulled. For the experiments, geckos were pulled on a glass surface by way of a small, gentle harness placed around their midsections.
“There were anecdotes before the study that geckos cannot stick to wet glass. We now know it is a bit more complicated than that. What we expect to learn is going to be relevant to synthetics and their capabilities to work not only on dry surfaces, but also wet and maybe, submerged ones,” Peter Niewiarowski says. “This implies a more versatile adhesive capability.”
After close study of the tiny hairs at the bottom of gecko feet that enable them to cling to surfaces, Dhinojwala and his colleagues have already developed a dry synthetic adhesive, comprised of carbon nanotubes, that outperforms nature’s variety. Now, with these new findings, Dhinojwala and his colleagues are one step closer to unfolding the secrets behind gecko toe adhesion in wetness.
MEDICA.de; Source: University of Akron