Discovery can lead to self-propelled robots – using only energy flow from their environment

Army-funded researchers have discovered how to make materials that can do self-propulsion so that materials can move without cars or hands.

Researchers at the University of Massachusetts Amherst have discovered how to make materials that can snap and repair themselves, relying solely on the energy flow from their environment. This research, published in Natural materials and funded by the U.S. military, could enable future military robots to move from their own energy.

“This work is part of a larger multidisciplinary effort to understand biological and engineered impulsive systems that will lay the foundation for scalable methods for generating forces for mechanical action and energy storage of structures and materials,” said Dr. Ralph Anthenien, Branch Chief, Army Research Office, an element of the U.S. Army to combat combat capabilities, now known as DEVCOM, Army Research Laboratory. “The work will have numerous possible future applications in operation and motive systems for the military and DOD.”

Researchers uncovered the physics during an everyday experiment that involved looking at a gel strip dry. The researchers noted that when the long, elastic gel strip lost internal fluid due to evaporation, the strip moved. Most movements were slow, but each time they accelerated rapidly.

These faster movements were snap instabilities that continued as the liquid further evaporated. Additional studies have revealed that the shape of the material matters, and that the strips can repair themselves to continue their movements.

“Many plants and animals, especially young ones, use special parts that work like feathers and latches to make them move fast, much faster than animals with muscles alone,” said Dr. Al Crosby, a professor of polymer science and engineering at the College of Natural Sciences, UMass Amherst. ‘Plants like the Venus flycatchers are good examples of this kind of movement, as are locusts and fall ants in the animal kingdom. ”

Snap instabilities are one way in which nature combines a spring and a latch and are increasingly used to create quick movements in small robots and other devices, as well as toys such as rubber poppers.

“However, most of these snap devices require a car or a human hand to keep moving,” Crosby said. “With this discovery, there may be different applications that do not require batteries or motors to replenish motion.”

After learning the essential physics from the drying strips, the team experimented with different shapes to find those that were likely to respond in expected ways, moving it repeatedly without cars or hands repairing it. The team even showed that the reformed strips could do work, such as climbing a staircase yourself.

“These lessons show how materials can generate powerful motion by using interactions with their environment, such as through evaporation, and this is important for designing new robots, especially in small sizes where it is difficult to control cars, batteries or other energy sources. have, “Crosby said.

The research team coordinates with DEVCOM Army Research Laboratory to transfer this knowledge and transfer it to future military systems.

Reference: “Autonomous snapping and jumping polymer gels” by Yongjin Kim, Jay van den Berg and Alfred J. Crosby, February 1, 2021, Natural materials.
DOI: 10.1038 / s41563-020-00909-w