How awesome! — assuming this isn’t some sort of hoax. It doesn’t sound like one, though; the photoreactive properties of dies like azobenzene are well-documented. I think I used some of the stuff myself in college for a lab and considered sprinkling some in my abominable roommate’s bed (damn him). Anyhow, the actual machine, built by researchers in Japan, relies on an elastic material impregnated with a light-sensitive dye that contracts or expands depending on what wavelength of light it’s exposed to.

The force of billions of atoms changing their conformation shouldn’t be underestimated, but at this point it’s not creating much torque. It’s apparently quite durable though, and I should think it’s easily scalable as well. The conversion of light to mechanical energy is pretty inefficient at the moment, but theoretically could still work over any distance. I can think of a million cool applications for this.