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... Barely visible to the naked eye, each robot measures about 200 by 300 by 50 micrometers, smaller than a grain of salt.

Operating at the scale of many biological microorganisms, the robots could advance medicine by monitoring the health of individual cells and manufacturing by helping construct microscale devices.

Powered by light, the robots carry microscopic computers and can be programmed to move in complex patterns, sense local temperatures and adjust their paths accordingly.

Described in Science Robotics and Proceedings of the National Academy of Sciences (PNAS), the robots operate without tethers, magnetic fields or joystick-like control from the outside, making them the first truly autonomous, programmable robots at this scale. ...