Nanoscale Polymer Strands Anchor New Adhesive

Originally Published MPMN October 2007

NEED TO KNOW

Nanoscale Polymer Strands Anchor New Adhesive

Brian Buntz

An independent research group has developed a glue that uses molecular bonds to maintain adhesion after multiple contact-and-release cycles. The polymer adhesive made by this university-based research team could have applications in the medical industry.

The glue, dubbed “geckel,” was inspired by natural adhesive properties demonstrated by the gecko and the mussel. Led by professor of biomedical engineering Phillip Messersmith at Northwestern University (Chicago; www.northwestern.edu), a research team created nanoscale arrays of silicone pillars modeled after the setae found on a gecko’s feet. When a gecko walks, these hair-like microscopic structures form a strong electrodynamic attraction with the surface underneath them that enables the lizard to scale vertical and inverted surfaces.

But the gecko’s impressive climbing capability suffers in the presence of moisture. The researchers thus turned to the mussel, which naturally produces a glue-like material that allows it to cling to rocks underwater—even as waves crash around it. To do so, the mussel excretes 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.”

The resulting adhesive “has the gecko-like features of temporary and reversible adhesion, but also can function on wet surfaces like a mussel,” according to Messersmith. By coating nanoscale strands with a polymer modeled on an amino acid found in a mussel’s adhesive protein, the researchers were able to combine both properties. The hybrid adhesive can withstand thousands of contact-and-release cycles and retains its 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. “It was particularly difficult finding a technique that would allow us to fabricate arrays of these pillars with high fidelity. Once we succeeded, application of the mussel adhesive protein mimetic polymer was actually quite easy,” he adds.

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 that tapes using the adhesive could be used to replace sutures and also may be useful as a water-resistant adhesive 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,” Messersmith explains.

Copyright ©2007 Medical Product Manufacturing News