Novel medical adhesive comes unstuck with ultraviolet light

Of all the minor-but-annoying pains in life, removing a sticking-plaster ranks unaccountably highly, especially if you are unlucky enough to have suffered an injury to hairy skin. It’s even generated an idiom, dividing people between the schools of “peel it off in little stages” and “go for one agonising rip”. But researchers in the US and China have now devised a new type of adhesive that can stick to moist surfaces strongly and yet be detached easily by exposing it to specific frequencies of light.

The research was directed by Zhigang Suo, a professor of mechanics and materials at the John A Paulsen School of Engineering and Applied Sciences (SEAS) at Harvard University, and also involved researchers from Xi’an Jiaotong University in China. “In nature, wet materials don’t like to adhere together,” Suo said. “We have discovered a general approach to overcome this challenge.”

Suo refered to his team’s discovery as “molecular sutures”. It occupies a middle ground between adhesion through covalent bonds, which would be permanent and is sometimes used to stick materials together in industry, and sticking through physical interactions, which is how current sticking plasters work. This sort of adhesive requires removal using solvents or simple brute force, leading to the familiar ouch. Molecular sutures work through a phenomenon known as topological entanglement, where polymer chains form a network between two pre-existing polymer networks: in this case, the substrate of whatever material needs to be stuck to the skin, and the surface of skin itself.