Fast acoustic tweezers for the two-dimensional manipulation of   individual particles in microfluidic channels
  This paper presents a microfluidic device that implements standing surface acoustic waves in order to handle single cells, droplets, and generally particles. The particles are moved in a very controlled manner by the two-dimensional drifting of a standing wave array, using a slight frequency modulation of two ultrasound emitters around their resonance. These acoustic tweezers allow any type of motion at velocities up to few 10mm/s, while the device transparency is adapted for optical studies. The possibility of automation provides a critical step in the development of lab-on-a-chip cell sorters and it should find applications in biology, chemistry, and engineering domains. 
S. B. Q. Tran (LIPhy), Philippe Marmottant (LIPhy), Pierre Thibault   (LIPhy)
physics.flu-dyn physics.class-ph