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Yang et al., Science Robotics 2020

Watch a tiny robot powered by alcohol

Robots tend to be powered by batteries and plug sockets. But the RoBeetle is a little different. This insect-size microbot (defined as weighing less than 1 gram) runs on methanol, a type of alcohol commonly found in solvents and antifreeze.

Liquid fuels like methanol hold more energy per unit volume than batteries, especially on a small scale. This means methanol-powered microbots don’t require an additional external power source, such as wires or electromagnetic fields. They could therefore theoretically move around with more autonomy than their electrically powered counterparts while retaining their minuscule size.

In a new study, researchers designed tiny artificial muscles that can contract and relax—just like the real thing. The system uses nickel-titanium alloy wires covered in a platinum powder, which speeds up the burning of methanol vapor. This produces heat, which causes wires in the robot’s legs to shorten and, after cooling, re-extend, driving the RoBeetle’s movement.

The RoBeetle weighs only 88 milligrams and can haul objects up to 2.6 times its own weight, the team reports today in Science Robotics. It can carry an additional 95 milligrams of fuel, which could power the robot for up to 2 hours. It’s also capable of climbing up slopes and can navigate surfaces with all kinds of different textures, including glass, a foam sleeping pad, and a concrete sidewalk.

Scientists now need to figure out how to refuel the robot to keep it continuously powered over longer periods. If they can program the RoBeetle to communicate with its human operator, methanol-powered microbots could one day act as artificial pollinators or assist complex surgeries.