The everyday magic of moisture absorption


Your most sophisticated lawn sprinkler system may rely on a junk-drawer staple. Because magic tape — that whisper-thin, nearly invisible wonder of modern household adhesion — holds not just daily utility but super-powers. Professor Babak Ziaie is working to unleash them.

The electrical and computer engineering professor owes this new path of research in large part to serendipity: “One of my students noted, basically by accident, that the tape absorbs moisture really well, and we got thinking —If it absorbs moisture, is able to bend and move, maybe we can use it to make sensors and soft robots. And we have.”

In the lab, Ziaie and his team have applied the tape, so to speak, to moisture sensor switches and millimeter-scale robotic swimmers, which he anticipates having utility for biomedical and environmental applications. Wherein previous navigable robotic swimmers relied on expensive metal oxides, the projects in Ziaie’s lab are turning plain old magic tape into eco-friendly devices that can be mass-produced economically.

A lot of the benefit of the tape has to do with the fact that its sticky and smooth sides behave differently when moisture comes into the picture.

“The tape has two layers — adhesive and backing — and they absorb moisture at different rates, which causes it to bend along the length of the tape,” Ziaie says. “We can use that feature to control how it moves. It’ll curl like a rocket nozzle, and gas comes from one end so it can move in the water.”

Laser ablation further dictates how the tape moves in the face of moisture or water. Video on Ziaie’s website (https://engineering.purdue.edu/ZBML/) includes some flashy demonstrations, but the practical applications are in the grand scheme much more impressive.

“We’re seeing a lot of potential in our sensors and robots — tiny grippers that utilize the tape,” Ziaie says. “It’s new, and we’ve had a lot of fun with it, as our videos show, but I’m sure we can do a lot more.”