Adhesive mimics gecko’s gravity-defying grip

TULANE (US)—A four-year-old gecko named Nikki is among a family of reptiles inspiring scientists to develop a new type of reusable dry adhesive. Researchers anticipate dry adhesives may one day be used as self-stick notes and page tabs that would not leave a residue, as bandages that would not fall off when wet, and possibly as adhesive pads on astronaut’s shoes.

When scientists began studying the gecko adhesive system, they discovered that geckos stick not by suction, or capillary forces, or by sticky substances on their toes, but by weak electromagnetic forces called van der Waals interactions.

It is the force of millions of nanoscale “split hairs” contacting a surface at once that gives the gecko a grip so strong it can hold its own body weight by a single toe, says Noshir Pesika, an assistant professor of chemical and biomolecular engineering at Tulane University.

Many research groups are fabricating structures of hair-like fibers attempting to replicate the gecko adhesive system. In his laboratory, Pesika is developing polymer-based dry adhesive structures. Details of the work are reported in the Journal of Physics: Condensed Matter.

Along with collaborators at the University of California, Santa Barbara, and Lewis & Clark College, Pesika has developed an innovative and simple technique to incorporate tilt in the hairy fibers. The angled fibers more closely duplicate the natural curve of the gecko hairs, which Pesika says exploits friction forces to enhance adhesion.

“We have structures that are already working,” Pesika says. “Our aim is to further improve adhesion and simplify the processing scheme to make the technology attractive to an industrial market.”

Dry adhesives have an advantage over traditional “sticky” adhesives, Pesika says, because they are a solid material that would not collect dirt and would still adhere in water or in space, where glue would evaporate.

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