Optical tweezers use light to immobilize microscopic particles as small as a single atom in 3D space. The basic principle behind optical tweezers is the momentum transfer between light and the object being held. Analogous to the water pushing on a dam that blocks the stream, light pushes onto and attracts objects that make the light bend. This so-called optical force can be designed to point to a certain point in space, where a particle will be held. In fact, the optical trapping technique has so far won two Nobel Prizes, one in 1997 for holding and cooling down single atoms, a second in 2018 for offering biologists a tool to study single biomolecules such as DNA and proteins.
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Source: Phys.org