Geckos walk up and down walls with the greatest of ease, thanks to tiny, spatula-shaped “hairs” on their feet that adhere and release (SN: 7/15/00, p. 47). Although materials researchers have made surfaces that borrow from the nanoscale design of gecko feet, the imitators’ adhesive power fades after repeated attachment and removal (SN: 6/7/03, p. 356), and they don’t work when wet.
To solve these problems, Phillip Messersmith and his colleagues at Northwestern University in Evanston, Ill., have contributed their knowledge of wet adhesives in mussels (SN: 12/18/04, p. 401). Mussels secrete a protein from their feet that bonds them to a variety of underwater surfaces. The sticky ingredient is the side chain of an amino acid, 3,4-dihydroxy-L-phenylalanine (DOPA).
The researchers used a mold to cast a network of gecko-style silicon-based pillars 400 nanometers in diameter and 600 nm tall. The team then coated the network with a thin, synthetic polymer containing the DOPA side chain. The resulting tapelike material can stick and restick more than 1,000 times and adheres almost as well in water as when dry, the researchers report in the July 19 Nature. The product is “kind of like a Post-it,” Messersmith says, albeit only half a square centimeter in size.
If they can find a method to produce larger swaths of the material, Messersmith and his colleagues envision a variety of medical applications, from bandages that stay put when wet to a tape alternative to surgical sutures. The team calls the new adhesive “geckel.”