Issue
EPL
Volume 87, Number 4, August 2009
Article Number 47003
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/87/47003
Published online 04 September 2009
EPL, 87 (2009) 47003
DOI: 10.1209/0295-5075/87/47003

Rapid fluid flow and mixing induced in microchannels using surface acoustic waves

M. K. Tan, L. Y. Yeo and J. R. Friend

Micro/Nanophysics Research Laboratory, Department of Mechanical Engineering, Monash University Melbourne, Victoria 3800 Australia

james.friend@eng.monash.edu.au

received 26 March 2009; accepted in final form 29 July 2009; published August 2009
published online 4 September 2009

Abstract
Very-high-frequency surface acoustic waves, generated and transmitted along single-crystal lithium niobate, are used to drive homogeneous aqueous suspensions of polystyrene nanoparticles along microchannels. At a few hundred milliwatts, uniform and mixing flows with speeds of up to 10 mm/s were obtained in centimetres-long rectangular channels with cross-sectional dimensions of tens to a few hundreds of microns. A transition from uniform to mixing flow occurs as the channel width grows beyond the wavelength of sound in the fluid at the chosen excitation frequency. At far lower input powers, the suspension agglomerates into equally spaced, serpentine lines coincident with nodal lines in the acoustic pressure field. We expose the physics underlying these disparate phenomena with experimental results aided by numerical models.

PACS
77.65.Dq - Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics.
47.61.-k - Micro- and nano- scale flow phenomena.
43.25.+y - Nonlinear acoustics.

© EPLA 2009