This remote-controlled robot crab can sit on the side of a penny

How small is Northwestern University’s robot crab? It’s sit-on-the-side-of-a-penny small. It’s half a millimeter wide — making it even smaller than a common flea.
Researchers behind it have determined a fairly simple way to control it remotely — when heat is applied to the system, its thin coating of glass deforms the system’s shape, creating locomotion in the process.
Using a laser, the robot can be quickly heated, owing to its tiny surface area. When the laser is turned off, it rapidly cools. Doing so in quick succession causes the robot to walk. To make it go left, the laser scans right to

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