A laminar flow expansion chamber facilitating downstream manipulation of particles concentrated using an ultrasonic standing wave

Microparticles (yeast cells) in flowing suspensions have been concentrated in bands in pressure nodal planes of a standing wave chamber driven at resonant frequencies ranging from its thickness fundamental of 0.66 MHz to its 15th harmonic. An outlet laminar flow expansion chamber preserves particle order for many centimeters downstream from the transducer. The 10 mm outlet width has the potential to facilitate the separation of concentrated microparticles from the clarified inter-band suspending phase, while the high frequencies utilised will allow manipulation of smaller microparticles. (C) 1998 Elsevier Science B.V. All rights reserved.