Fire-powered 3-D printed robot can jump like a frog

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Time and time again the animal kingdom has provided robot-makers with inspiration for their next great machine. There are the bots that run like cheetahs, crawl like centipedes, soar through the air like flying snakes. Now a team at Harvard has built a leaping robot that can jump like a frog.

The robot itself is the size of a dinner plate and looks like a stack of plunger cups. It takes off like a rocket, getting a boost from an explosive blast of butane and oxygen ignited under its central dome. The bot can reach about three feet with each jump, and if it starts at an angle, can jump sideways too.

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But the big technical leap here is that it’s a hardy fellow that can survive the landing after flying through the air. The plunger cups gradually vary in stiffness — which means it can absorb the shock of landing, while also staying upright and firm.

“We were really happy with how well it’s held up with jumping and surviving the explosion and falling from a number of feet,” said Nicholas Bartlett, a Harvard graduate student who was among the robot’s creators.

The unconventional body shape also makes it a reliable jumper, the team explained in a paper published Thursday in the journal Science.

Before they are put to use, robots must be able to carry their power source on their back. Bartlett said that this is a first demonstration of how a combination of hard and soft materials, 3-D-printed in a gradient, is a step toward more capable, hardier robots that can move independently.

This model, for example, could navigate easily over obstacles on turf that may be a challenge for a robot with wheels. If it’s part of a search rescue mission and falls from a height, for example, it would be no big deal.

The new model is a shift in the field that is turning a laser focus on soft machines, creating parts like hands out of tough stretchy polymers rather than metal. The advantages: More versatility, and an inbuilt degree of safety when they work with or around humans.

“Soft robotics has the potential to do a lot of cool things that traditional rigid robots can’t do,” Bartlett said.

For example, Harvard spinout Soft Robotics is already testing its models of soft, air-powered grippers to produce manufacturers in the food industry because their robotic hands can be gentle with fruit. The co-founder of that company, Harvard professor George Whitesides, is also part of the team that built this new jumping robot.

So it’s no surprise that it shares some DNA with other soft robots that have emerged from his lab. Among its predecessors are a fully-flexible soft robot that looks like a four-legged starfish, is powered by air, and can carry a battery on its back.

Nidhi Subbaraman writes about science and research. Email her at nidhi.subbaraman@globe.com.
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