A robot beetle goes the distance on its own thanks to a methanol-fueled micromuscle.

Scientists envision that swarms of robotic insects could assist search-and-rescue operations (SN: 5/19/16). But tight spaces are out of reach for robots that must be tethered to an energy source. The new bot, described August 19 in Science Robotics, carries its liquid fuel inside its body.

“I realized the critical issue was power,” says Néstor O. Pérez-Arancibia. His team at the University of Southern California in Los Angeles turned to methanol because in a given mass, it packs over 10 times the energy as tiny batteries.

To turn methanol into motion, the researchers coated a nickel-titanium alloy wire with platinum. The alloy contracts like a muscle when heated, and extends once cool. The platinum generates heat by combusting any methanol vapor that comes in contact with it. By varying the exposure to fuel in a periodic pattern, the temperature varies and the micromuscle accordions. That motion causes the bot’s forelegs to rear up. When the legs scooch back again, the body drags forward.

This beetle bot may weigh only as much as three grains of rice but to crawl it needs a tiny yet mighty source of fuel. Instead of tethering it to a power source, scientists stowed methanol inside the robot’s body, where it powers an artificial micromuscle. That self-contained fuel could be a crucial advance in creating bots that can swarm into tight spaces during search-and-rescue missions.

Excluding fuel, the beetle bot weighs about as much as three grains of rice, on par with live insects. It crawls on flat surfaces while carrying up to 2.6 times its weight. It tackles inclines steeper than the toughest treadmill setting. And it can run for over one hour, Pérez-Arancibia says. With a battery — even a state-of-the-art one — it would run for a few seconds at best, he estimates.

There’s room for improvement: The beetle is slower than comparable robots and can’t be steered. Next-generation prototypes will use the same artificial muscle principle with a speedier, more maneuverable design and a different fuel.

Flying robots are his ultimate goal. Specifically? “We want to do butterflies,” he says.

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