Engineering Minute

Engineering Minute – Reversible Adhesive Inspired By Snail Slime

Engineers at the University of Pennsylvania have developed a reversible adhesive that is inspired by the mechanics of snail slime. The adhesive is comprised of a polyhydroxyethylmethacrylate (PHEMA) hydrogel that is rubbery when wet but becomes rigid when dry. The properties of the adhesive are reversible when wet, allowing it to be reset if needed. Their work was recently published in the journal Proceedings of the National Academy of Sciences.

 

“When it’s conformal and rigid, it’s like super glue. You can’t pull it off. But, magically, you can rewet it, and it slips off effortlessly,” says study lead Shu Yang, professor at the University of Pennsylvania's School of Engineering and Applied Science. “Additionally, PHEMA doesn’t lose its strong adhesion when scaled up. Usually, there’s a negative correlation between adhesion strength and size. Since PHEMA is not dependent on a fragile structure, it doesn’t have that problem.”

 

 Snails can anchor themselves in place using a structure known as an epiphragm. The snail’s slimy secretion works its way into the pores found on even seemingly smooth surfaces, then hardens, providing strong adhesion that can be reversed when the slime softens. Penn Engineers have developed a new material that works in a similar way.
Snails can anchor themselves in place using a structure known as an epiphragm. The snail’s slimy secretion works its way into the pores found on even seemingly smooth surfaces, then hardens, providing strong adhesion that can be reversed when the slime softens. Penn Engineers have developed a new material that works in a similar way. Credit: University of Pennsylvania

From the University of Pennsylvania article: "To demonstrate just how durable their PHEMA adhesive is, one of Yang’s lab members and co-first author, Jason Christopher Jolly, volunteered to suspend himself from a harness held up only by a postage-stamp-sized patch of their adhesive; the material easily held the weight of an entire human body. Based on the lab tests, the team determined that, although PHEMA may not be the strongest adhesive in existence, it is currently the strongest known candidate available for reversible adhesion.

With that kind of power, the snail-slime adhesive could have a big impact on the scientific field as well as in industry. Yang sees durable, reversible adhesives like her PHEMA hydrogel as having massive potential for household products, robotics systems, and industrial assembly.

Despite its promise in applications like heavy manufacturing, PHEMA is not a fit for most industries because its reversibility is controlled by water. While water is the perfect control mechanism for a snail, you wouldn’t want your car to fall apart in the rain. So, although PHEMA is the first of its kind in reversible adhesion, Yang acknowledges that it’s just a starting point."

 

Read more about the reversible adhesive inspired by snail slime at the University of Pennsylvania