A hand-held laser pointer produces no noticeable recoil forces when it is "fired"—even though it emits a directed stream of light particles. The reason for this is its very large mass compared to the very small recoil impulses that the light particles cause when leaving the laser pointer.
However, it has long been clear that optical recoil forces can indeed have a very large effect on correspondingly small particles. For example, the tails of comets point away from the sun partly due to light pressure. The propulsion of light spacecraft via light sails has also been discussed repeatedly, most recently in connection with the "star shot" project, in which a fleet of miniature spacecrafts is to be sent to Alpha Centauri.
In the journal Nature Nanotechnology, Würzburg physicists led by Professor Bert Hecht (Chair of Experimental Physics 5, Nano-Optics Group) have now shown for the first time that it is possible to not only efficiently propel micrometer-sized objects in an aqueous environment with light, but also control them precisely on a surface with all three degrees of freedom (two translational plus one rotational).
To read more, click here.