NCSU Researchers Build Faster Thermal Actuator

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Actuator in motion

The actuator’s unique bistable design allows it to move back and forth quickly with changes in temperature. | Source: North Carolina State University

A research team from North Carolina State University (NCSU) developed a faster thermal actuator for soft robotic devices. Actuators create motion by converting energy into work.

“The use of thermal actuation isn’t new for soft robots, but the biggest challenge for soft thermal actuators was that they were relatively slow – and we made them fast,” Yong Zhu, corresponding author of the article and Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at NCSU, said.

The key to the team’s rapid actuator movements is its bistable design, and its preferred shape is temperature dependent.

The research team placed silver nanowires between two layers of different materials on top of each other. The two materials will heat and expand at different temperatures, as this happens the structure will bend.

At some point, once the structure reaches a critical temperature, it falls into place. Once it clicks into place, the structure is stable again. The same process occurs when the structure cools down. The critical temperatures, however, will be different with the critical heating temperature being higher.

“Think of a hair clip. It’s stable until you apply a certain amount of energy (by bending it), and then it takes on a different shape – which is also stable, ”Shuang Wu, first author of the article and PhD . student at NCSU, said.

The researchers created two prototypes to test their method. The first closes or opens, imitating the movement of a Venus fly trap. The second’s slamming motion helps him crawl, moving at more than one body length per second.

The actuator has potential applications in a variety of industries, from biomedical applications to manufacturing.

In the future, the team hopes to automate the process by creating sensors and control mechanisms.

“We are also interested in exploring other possible materials, so that we can refine the thermal and mechanical properties,” Zhu said. “This could allow us to match both the speed and the force of the actuator.”

Editor’s Note: You can read the whole team’s research here.

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