TECHNOLOGY NEWS: ADHESIVES
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Geckel adhesive was inspired by adhesion shown by geckos and mussels.
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A research group has developed a glue that uses molecular bonds to maintain adhesion through multiple contact-and-release cycles. Dubbed “geckel,” the glue was inspired by natural adhesive properties demonstrated by geckos and mussels. The research group that developed the glue, led by professor of biomedical engineering Phillip Messersmith at Northwestern University (Chicago, IL, USA), created nanoscale arrays of silicone pillars modeled after the setae found on geckos’ feet. When a gecko walks, these hair-like microscopic structures create an electrodynamic attraction with the surface underneath them that enables the lizard to scale vertical and inverted surfaces. The gecko’s impressive climbing capability suffers, however, in the presence of moisture.
The researchers thus turned to the mussel, which produces a glue-like material that allows it to cling to rocks underwater—even as waves crash around it. Mussels accomplish this trick by excreting a protein adhesive that simultaneously displaces water molecules and binds oxygen atoms within it to metallic or mineral atoms. “I came up with the idea for geckel about two years ago after reading how geckos cannot adhere well underwater,” Messersmith says. “Having done several years of research on mussels’ adhesive proteins, it occurred to me that we might be able to borrow ideas from both organisms to come up with a hybrid adhesive,” he explains.
The adhesive developed by Messersmith’s group “has the gecko-like features of temporary and reversible adhesion,” says Messersmith, “but also can function on wet surfaces like a mussel.” The researchers were able to combine both properties by coating nanoscale strands with a polymer modelled on an amino acid found in mussels’ adhesive protein. The resulting hybrid adhesive can withstand thousands of contact-and- release cycles and retains bonding power when submerged in liquid. “The biggest challenge when developing the adhesive was fabricating the array of polymer pillars that mimic the gecko’s setae,” Messersmith notes. “Once we succeeded, application of the mussel adhesive protein mimetic polymer was actually quite easy.”
Although Messersmith believes that it could be several years before the new adhesive hits the marketplace, he is confident that geckel will be used in a variety of areas including industrial, medical, and consumer products. In the medical sphere, he predicts tapes using the adhesive could be used to replace sutures and also as a water-resistant ad- hesive for bandages, drug-delivery patches, and other medical materials that must adhere to the skin. “For instance, the glue could be used for adhesion of ostomy bags to the skin for several days while allowing easy removal from the skin,” he explains.
