Engineer makes squishy robots because 'instabilities are fun' -- and useful

Researchers embrace the wobbliness of soft materials to make squishy robots.

March 14, 2019, 4:19 PM

This is an Inside Science story.

(Inside Science) -- When you think of robots you probably picture something made of cold hard metal, or maybe smooth plastic armor. But what about a soft robot with no gears or wires? Katia Bertoldi, an engineer at Harvard University, and her colleagues are all about building robots with squishy and soft materials. She shared some of the designs at a meeting of the American Physical Society last week in Boston.

Drawing inspiration from snakeskin, Bertoldi’s team built a special suit that turned a simple balloon into a moving robot. They applied cutting techniques from the Japanese art known as kirigami -- which they had learned from previous projects -- to give the suit scale-like skin that would flare open when stretched, and close again when relaxed.

The repetitive flaring and closing of the scales created a motion that pulled the robot forward and was only possible using a soft material. In the past, these materials were usually avoided when designing robots because they are hard to control.

"Traditionally we design systems to avoid instabilities," said Bertoldi. "But I'm convinced that instabilities are fun, and we can use them to advance the functionalities of certain systems."

To further illustrate her point, Bertoldi shared another contraption made of soft chambers that can be expanded and contracted using fluidic pumps. It can be used as a simple motor when combined with other components such as legs and claws.

The chambers are made by nesting and sealing two rubber poppers of different sizes atop each other. When the poppers snap, the chambers flex in heartbeatlike pulses. In the future, Bertoldi said they will try using poppers with different stiffnesses as valvelike components that can selectively transfer energy along different channels connected by soft tubes.

These soft components are useful for making soft robotic systems, which in the future may replace their current hard counterparts one by one, making future robots more flexible.

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