This isn't the first Nobel for optical tweezers. Steve Chu used them in atom trapping experiments at Bell Labs, although the award is for the atom trap results, not for the tweezers themselves.
Chu's prize was for laser cooling, which uses a magneto-optical trap. Magneto-optical traps confine atoms by exploiting the Zeeman effect, a spatially-varying magnetic field, and a laser with a precisely-controlled wavelength tuned to be slightly red of an electronic transition. Optical traps, on the other hand, rely on the refraction of a much larger, but still microscopic, object.
Some of Chu's work uses an optical trap, but that work did not earn his prize.
Some of Chu's work uses an optical trap, but that work did not earn his prize.