The devices harness the so - called gradient optical force, by which a light beam can exert a push or pull in a direction transverse, or perpendicular, to the direction of the light's propagation. (scientificamerican.com)
While optical forces such as radiation pressure have been studied and harnessed for a while, angular momentum and the force it induces, optical torque, have remained relatively unexplored. (sciencedaily.com)
According to Konstantin Bliokh, the corresponding author of the paper, «Our findings revisit fundamental momentum properties of light and, revealing a new type of optical force, enrich optomechanics.» (sciencedaily.com)