Ultrasonic particle manipulation in microchannels using phased co-planar transducers

We report the demonstration of a new, simple and flexible method of performing ultrasonic particle manipulations within planar microfluidic systems, using a set of ultrasonic transducers co-located on the top (or bottom) of a microchannel and driven with out-of-phase electrical signals. This method allows for the generation of in-plane standing waves while overcoming the integration challenges that have previously hindered the use of ultrasonic methods within microfluidic lab-on-a-chip or micro total analysis systems (/spl mu/TAS). We present the design of a simple device consisting of a pair of co-planar lead zirconate titanate (PZT) transducers mounted atop an anisotropically etched microchannel, including structural and acoustic finite element analysis (FEA) predictions of the device performance. Test results on suspensions of polystyrene beads show that the performance is in accordance with the analyses and with acoustic radiation force theory. We describe ongoing work on the development of a variety of more advanced and highly integrated devices, based on this method, that are suitable for performing a wide range of ultrasonic particle manipulations within microfluidic systems.