On the bi-weekly seminar of the Journal Experiments in Fluids Christian reported on the latest developments of our research on surface acoustic waves. The complete talk can be found in here:

https://www.youtube.com/watch?v=wCfFpUCQ_xA

Abstract: Acoustic fields can be used in microfluidic devices to manipulate particles for example for the fractionation of particle suspensions or the transport and alignment of cells in biological assays. Using so called interdigital transducers on piezo-electric substrates surface acoustic waves (SAW) can be excited by applying high frequency electric signals. The superposition of different SAW can produce complex acoustic fields and pressure distributions in the bulk volume of a microchannel. In principle two forces act on the particles. The scattering of the acoustic waves on suspended particles results in the acoustic radiation force that influences their motion. Due to viscous damping of radiated waves within a fluid, a superimposed fluid flow is generated due to the acoustic streaming effect. This flow will also act on the particles by drag forces. As the boundary conditions and the physical phenomena for such systems are unknown or at least associated with a high degree of uncertainties, experimental approaches play a key role for the characterization of SAW-based microfluidics. In the current presentation astigmatism particle tracking will be introduced for 3D3C velocity measurements in conjunction with lifetime imaging to simultaneously measure the temperature in SAW devices. The data will be complemented by laser vibrometer measurements of the wave field to shed more light on the complex physics.