Inspired by Rubber Popper Toy, Harvard Researchers Create a Fast-Moving Jumping Soft Robot Actuator

Researchers from Harvard University have designed a soft robot capable of hopping — and took inspiration from a classic and simple children's toy.

"Soft robots have enormous potential for a wide spectrum of applications, ranging from minimally invasive surgical tools and exoskeletons to warehouse grippers and video game add-ons," explains co-first author Benjamin Gorissen of his team's work. "But applications for today’s soft actuators are limited by their speed."

That speed problem relates to fluidic soft actuators, which require gas or liquid to be pumped into them to move — and the bigger the actuator, the more gas or liquid they require and the slower they are to actuate. "In this work, we showed that we can harness elastic instabilities to overcome this restriction," says fellow co-first author David Melancon, "enabling us to decouple the slow input from the output and make a fast-jumping fluidic soft actuator."

The inspiration of for the system: Toy poppers, small rubber half-spheres which are turned inside out to set running what is effectively a mechanical timer made wholly out of rubber. When the timer runs out, the popper violently inverts back to its original shape — propelling itself into the air with a pop.

The same concept is used in the team's soft robot: Shell buckling, the mechanical effect that makes a toy popper pop, is used to create an an actuator which is effectively two toy poppers joined together at the base. As air is pumped into the assembly, the thinner outer cap expands and the thicker inner cap quickly buckles and collapses — propelling the actuator into the air just like the toy popper.

"This actuator is a building block that could be integrated into a fully soft robotic system to give soft robots that can already crawl, walk and swim the ability to jump," adds Professor Katia Bertoldi, senior author of the study. "By incorporating our jumper into these designs, these robots could navigate safely through uncharted landscapes."

The team's work has been published under closed-access terms in the journal Science Robotics.