Sticky when wet — spider glue tightens grip in high humidity

Spider glue droplets decrease in viscosity with an increase in humidity levels. University of Akron scientists say spiders’ adaptive web glue gives clues and promise to the development of smart adhesives that grip firmly under high humidity conditions.

Envision a bandage that sticks to your skin in the shower. University of Akron researchers are taking tips from nature to develop a smart adhesive that tightens its grip when wet.

Gaurav Amarpuri, University of Akron Ph.D. candidate in polymer science, along with UA professors Ali Dhinojwala and Todd Blackledge, joined Virginia Tech professor Brent Opell to study spider glue adhesion. They found that spiders make glue with maximum stickiness at the humidity matching the natural habitat of the spider.

Some spider species found near rivers that are active in highly humid environments use glue that is stickiest in 100 percent humidity. Species active in dry environments have glue that is maximally sticky at lower humidity, explains Opell. 

In all, the researchers examined five species of spiders in dry to wet conditions. They studied the viscosity, or “fluidity,” of spider web glue droplets by using high-speed video to measure the rate at which the droplets spread. The lower a droplet’s viscosity, the more quickly it spread.

Depending on the level of humidity, the consistency of spider glue changed from that resembling olive oil to peanut butter, says Dhinojwala, Morton Professor of Polymer Science.

Spiders adapt with ease

“The intuitive ability of spiders to adapt the viscosity of their web glue to catch prey in dry to highly humid conditions is beautiful to observe in these experiments.” says Amarpuri, explaining that all five of the species similarly evolved humidity-responsive glue. 

"We are taking a closer look at the role of proteins and salts in spider glue in controlling viscosity and adhesion and how they might be applied to creating tomorrow’s smart adhesive," explains Blackledge, a professor of biology.

Inspired by nature, in this case – spider glue adhesion – the scientists are exploring the possibility of developing synthetic glue that adapts its adhesion in humid conditions.

Their study was published in journal ACS Nano. 

Media contact: Denise Henry, 330-612-0494 or henryd@uakron.edu.