From Arnold's lab: Microscope-captured video shows a viral-sized nanoparticle pulled toward a microsphere and caused to orbit by light forces. For more details see "more info" on the YouTube side-bar.

Stephen Arnold, Institute and Thomas Potts Professor of Physics, and director of Polytechnic’s MicroParticle PhotoPhysics Lab (MP3L), presented lectures at a NATO Advanced Study Institute in Erice, Italy this July about his lab’s discoveries in nanoparticle transport by light.

His presentations centered on a technique he has dubbed an “optical tractor beam” which draws individual viral-sized nanoparticles toward the Whispering Gallery Mode Biosensor he invented with Iwao Teraoka of the Chemical and Biological Sciences Department. A prototype of the biosensor is able to detect individual viruses and other infectious agents in real-time, a potential clinical dream-come-true.

The tractor beam enhances the biosensor’s sensitivity by attracting nanoparticles and propelling them into orbit about the microspherical sensor’s equator (you can see an example of the process in the above video). 

A publication describing this advance, which creates a new area for nanoparticle transport by light, is available online.