Controlled rotation of biological micro- and nano-particles in microvortices.

Micrometer-sized re-circulating flows generated in a microfluidic system are used to drive the controlled rotation of biological particles of both micro- and nano-meter scale dimensions. This technique is independent of the intrinsic nature of the particle, and possesses the potential to rotate particles at high rates. We demonstrate in such microvortices the orientation control of single DNA molecules, and the axial rotation of biological cells in which the cellular contents were visibly affected by rotation.