Diminutive device can leap 23 times its body length

Springtails, small bugs often found crawling through leaf litter and garden soil, are expert jumpers. Inspired by these hopping hexapods, roboticists at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have made a walking, jumping robot that pushes the boundaries of what small robots can do.

Published in Science Robotics, the research glimpses a future where nimble microrobots can crawl through tiny spaces, skitter across dangerous ground, and sense their environments without human intervention.

The new Harvard robot was created in the lab of Robert J. Wood, the Harry Lewis and Marlyn McGrath Professor of Engineering and Applied Sciences at SEAS. It is a modification of the Harvard Ambulatory Microrobot (HAMR), a microrobotic platform originally modeled after the dexterous, hard-to-kill cockroach.

Now, HAMR is outfitted with a robotic furcula—the forked, tail-like appendage tucked under a springtail’s body that it pushes off the ground to send it into the air.

“Springtails are interesting as inspiration, given their ubiquity, both spatially and temporally, across evolutionary scales,” Wood said. “They have this unique mechanism that involves rapid contact with the ground, like a quick punch, to transfer momentum and initiate the jump.”

To go airborne, the robot uses what’s called latch-mediated spring actuation, in which potential energy is stored in an elastic element—the furcula—that can be deployed in milliseconds like a catapult. This physical phenomenon is found time and again in nature, not just in springtails: from the flicking tongue of a chameleon to the prey-killing appendage of a mantis shrimp.

Wood’s team previously created a mantis shrimp-inspired punching robot. “It seemed natural to try to explore the use of a similar mechanism, along with insights from springtail jumps, for small jumping robots,” Wood said.

The springtail’s furcula is also elegantly simple, composed of just two or three linked units. “I think that simplicity is what initially charmed me into exploring this type of solution,” said first author and former SEAS research fellow Francisco Ramirez Serrano.

The team used streamlined microfabrication workflows pioneered in the Wood lab to develop the palm-sized, paper clip-light robot that can walk, jump, climb, strike, and even scoop up objects.

The robot demonstrates some of the longest and highest jumps of any existing robot relative to body length; its best performance is 1.4 meters, or 23 times its length. By contrast, a similar robot can jump twice as far but outweighs the Harvard robot by 20 times.

“Existing microrobots that move on flat terrain and jump do not possess nearly the agility that our platform does,” Serrano said.

The team incorporated detailed computer simulations into the design of the robot to help it land optimally every time, precisely controlling for the lengths of its linkages, the amount of energy stored in them, and the orientation of the robot before takeoff.

Packing all manner of athletic abilities into one lightweight robot has the team excited for a future where robots like theirs could traverse places humans can’t or shouldn’t.

“Walking provides a precise and efficient locomotion mode but is limited in terms of obstacle traversal,” Wood said. “Jumping can get over obstacles but is less controlled. The combination of the two modes can be effective for navigating natural and unstructured environments.”