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Soft robots autonomously navigate mazes using ambient heat energy

Image credit: Parrish Freeman | Unsplash

Soft robots that are capable of navigating complex environments such as mazes, without any input from humans or computer software, have been developed by researchers from North Carolina State University and the University of Pennsylvania.

“These soft robots demonstrate a concept called ‘physical intelligence,’ meaning that structural design and smart materials are what allow the soft robot to navigate various situations, as opposed to computational intelligence,” said corresponding author of the study, Jie Yin.

The soft robots are made of liquid crystal elastomers in the shape of a twisted ribbon, resembling translucent rotini.

When the ribbon is placed on a surface that is at least 55°C, which is hotter than the ambient air, the portion of the ribbon touching the surface contracts, while the portion of the ribbon exposed to the air does not.

This induces a rolling motion in the ribbon: the warmer the surface, the faster it rolls.

“This has been done before with smooth-sided rods, but that shape has a drawback: when it encounters an object, it simply spins in place,” Yin said. “The soft robot we’ve made in a twisted ribbon shape is capable of negotiating these obstacles with no human or computer intervention whatsoever.”

The ribbon robot does this in two ways. First, if one end encounters an object, the ribbon rotates slightly to get around the obstacle. Second, if the central part of the robot encounters an object, it 'snaps'.

The snap is a rapid release of stored deformation energy that causes the ribbon to jump slightly and reorient itself before landing. The ribbon may need to snap more than once before finding an orientation that allows is to negotiate the obstacle, but ultimately it always finds a clear path forward, the researchers said.

“In this sense, it’s much like the robotic vacuums that many people use in their homes,” Yin added, “except the soft robot we’ve created draws energy from its environment and operates without any computer programming.”

Yao Zhao, first author of the paper, added: “The two actions, rotating and snapping, allow the robot to negotiate obstacles operate on a gradient.

“The most powerful snap occurs if an object touches the centre of the ribbon. The ribbon will still snap if an object touches the ribbon away from the centre, it’s just less powerful. The further you are from the centre, the less pronounced the snap, until you reach the last fifth of the ribbon’s length, which does not produce a snap at all.”

The researchers conducted multiple experiments demonstrating that the ribbon-like soft robot is capable of navigating a variety of maze-like environments. The researchers also demonstrated that the soft robots would work well in desert environments, showing they were capable of climbing and descending slopes of loose sand.

“This is interesting, and fun to look at, but more importantly it provides new insights into how we can design soft robots that are capable of harvesting heat energy from natural environments and autonomously negotiating complex, unstructured settings such as roads and harsh deserts.” Yin said.

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