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Harvard researchers develop 3D printed 'hopping' soft robot

12 July 2015

Harvard engineers have used 3D printing to combine the autonomy and speed of a rigid robot with the adaptability and resiliency of a soft robot.

The hopping robot (photo: Harvard Microrobotics Lab)

Described in a recent issue of the journal, Science, the design offers a new solution to an engineering challenge that has plagued soft robotics: the integration of rigid and soft materials.  

The robot’s body transitions from soft to hard, reducing the stress where the rigid electronic components join the body and increasing the robot’s resiliency. The body’s monolithic design — created in one continuous print job, using several different materials — increases its strength and robustness. 

With no sliding parts or traditional joints, the robot isn’t victim to dirt or debris like its more intricate cousins, making it a good candidate for use in harsh terrains.

“The vision for the field of soft robotics is to create robots that are entirely soft,” says Harvard's Professor Robert Wood. “But for practical reasons, our soft robots typically have some rigid components — things like batteries and control electronics.

"This robot is a demonstration of a method to integrate the rigid components with the body of the soft robot through a gradient of material properties, eliminating an abrupt hard-to-soft transition that is often a failure point.”

The combustion-powered robot comprises two main parts: a soft plunger-like body with three pneumatic legs and a rigid core module containing power and control components and protected by a semi-soft 3D printed shield.

To initiate movement, the robot inflates its pneumatic legs to tilt its body in the direction it wants to go. Then butane and oxygen are mixed and ignited, catapulting the robot into the air. It’s a powerful jumper, reaching up to six times its body height in vertical leaps and half its body width in lateral jumps. In the field, the hopping motion could be an effective way to move quickly and easily around obstacles.

“The wonderful thing about soft robots is that they lend themselves nicely to abuse,” says Harvard SEAS graduate student, Nicholas Bartlett, first author of the Science paper. “The robot’s stiffness gradient allows it to withstand the impact of dozens of landings and to survive the combustion event required for jumping."


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