Robot SHOOTS into the air with hot gas from its soft round behind

Harvard uni boffins have 3D printed a robot with a soft butt able to belch hot gases, thus unleashing a remorseless and invincible-ish hopping trouser-cough machine.

An article titled A 3D-printed, functionally graded soft robot powered by combustion describes the bot in the 10 July issue of Science.

The new design offers a fresh solution to the engineering challenge that the Harvard Gazette claims "has plagued soft robotics: the integration of rigid and soft materials."

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"The vision for the field of soft robotics is to create robots that are entirely soft," said senior author Robert J. 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 bot has two main parts: a soft plunger-like body with three pneumatic legs and a rigid core module which containing power and control components.

The core module is protected by a semisoft shield created with a 3D printer.

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, exploding the robot into the air.

Harvard believe it is a mighty hopper, 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," said Nicholas Bartlett, first author of the 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. Consequently, the robot not only shows improved overall robustness but can locomote much more quickly than traditional soft robots."

The new design is intended to demonstrate the potential of 3D printing in soft robotics. Traditional methods of fabrication, including custom molds and multistep assembly, are obviously costly and slow.

The increasing breadth of materials compatible with 3-D printers is allowing engineers to prototype new designs faster and putting to bed the old adage that increased complexity necessarily leads to increased cost.

"Soft robotics is a relativity nascent subfield, and 3-D printing is adding to the repertoire of things we can do in a really practical way," said Wood. ®