Beetlebot carries heavy loads using alcohol-powered artificial muscles

One of the world's smallest microrobots is able to carry 2.6 times its own body weight thanks to a muscular system powered by alcohol. Conventionally, the "muscles" of small robots have been tethered to an external power source. Alternatively, they have been powered by batteries, the weight and size of which have limited efficiency and how small the robots can be. Top-of-the-range batteries have an energy density of around 1.8 megajoules per kilogram, a fraction of what you get from animal fat, which is about 38 MJ/kg. The methanol-powered muscles used by RoBeetle, an 88-milligram-long microrobot, can use catalytic combustion to reach energy levels up to 20 MJ/kg.