'In robotics, as in so many things, small is beautiful. The trouble is that making them really small is very nearly impossible. “Building robots that operate independently at sizes below one millimeter is incredibly difficult,” says roboticist Marc Miskin at the University of Pennsylvania. “The field has essentially been stuck on this problem for 40 years.”

Now researchers at Penn and the University of Michigan have created the world’s smallest, fully programmable, autonomous robots, packing significant capacities into a device smaller than a grain of salt. These are parsimonious little things, barely visible to the naked eye yet able to sense their environment, respond to it and move around in complex patterns. As described in a new paper in the journal Science Robotics, they run on infinitesimally small quantities of energy and gain power from light.

“These are the smallest programmable autonomous robots that I have seen,” said Kevin Chen, an MIT roboticist who wasn’t involved. “This is an exciting advance for the nanorobotics community.”

Miskin’s team at Penn provided the propulsion system. The robots work in liquid environments and move by generating a tiny electrical field that pushes on nearby water molecules. Lacking tiny arms and legs, which are hard to make and easy to break, the robots are quite durable and can swim for months as long as they have an energy source.'

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