P5G-2 Acoustic Surface Wave Induced Propagation of Liquids in Open Channels

The propagation of liquids induced by acoustic streaming turned out to be a successful approach, but applications seem to be restricted to small dimensions of the liquid channel in the order of some tens of micrometers and to piezoelectric substrate materials. In this contribution another approach will be described, which allows to extent the dimension of liquid channels to the order of some millimetres or centimetres and allows the use of common structural materials like metals, glass or ceramics as substrates for the propagation of surface acoustic waves: Rayleigh-like waves are excited on the interface of the substrate to the liquid by piezoelectric interdigital transducers attached to the backside of the substrate, from which sound waves are radiated off into the liquid under a characteristic angle determined by the velocities of waves in the liquid and on the substrate, respectively. Results of liquid propulsion in open channels obtained with such a set up will be presented, which demonstrate the contributions of different mechanisms of momentum transfer like e.g. acoustic streaming due to wave propagation along the channel bottom surface, sound absorption in the liquid ("quartz wind") and sound reflection at liquid surfaces.