The light mill's direction of rotation can be changed by altering the frequency of the laser light (Image: Zhang group)
OK, first of all, what’s a light mill? It’s a simple rotary motor consisting of four flat vanes mounted to a central axis, which spins when subjected to light. Light mills have been around since 1873, mostly just as novelty items, and have pretty much always been at least a few inches tall. Less than a week ago, however, scientists at California’s Lawrence Berkeley National Laboratory announced the creation of a light mill just 100 nanometers in size. Unlike its bigger brothers, this tiny device might actually have some very practical applications.