Sub-micro Tetris

A real-life implementation of the evergreen arcade game Tetris was obtained by optically trapping 42 glass microspheres (1 μm diameter) in a 25 μm x 20 μm sized field under a microscope. Their positions are then steered with a computer.
The generation of multiple traps, as well as the computer-steering, is accomplished by the use of acousto-optic deflectors: devices that tune the deflection of a laser beam that have very fast response.