A faint, fatty residue found in gecko footprints may finally solve the riddle of these lizards' ability to stick to walls and ceilings. Researchers believed that molecular interactions between the microscopic branching hairs  on the gecko's footpads and the surface to which they clung were responsible for the gravity-defying feats. A team of researchers, however, noticed that the geckos had footprints; that is, they left behind a slight residue as they walked. Analysis of the residue, published today in the Journal of the Royal Society Interface, showed that it consisted primarily of fats known as phospholipids. These compounds may help protect the delicate hairs on the gecko's toes, as the hairs never showed any signs of wear. The lipids might also provide a liquid-like layer that makes the lizard's toes cling better . And that could help materials scientists trying to create an adhesive-free, reusable tape that mimics the geckos' sticky skills.
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