A microfluidic system combining acoustic and dielectrophoretic particle preconcentration and focusing

Microfabricated systems have recently become useful for routing particles to precise locations in microfluidic channels. In this paper we discuss the modeling, fabrication and characterization of such a platform that combines acoustic forces and ac dielectrophoresis (DEP). This system integrates a bulk lead zirconate titanate (PZT) slab with substrate patterned microelectrodes for DEP manipulation of particles. Moreover, a one-dimensional transmission line model is presented to understand the coupling of the acoustic and dielectrophoretic transducers with the microdevice. While the acoustic model does not predict the lateral coupling in the system, it does provide some insight into axial (thickness-mode) frequencies of operation. Experiments are also conducted in which particles were routed into a large (0.75 mm wide) microchannel and preconcentrated and focused into coarse bundles by coupling an acoustic wave into the channel. Subsequently, particles are further focused into single file particle streams using interdigitated DEP electrodes. This system can be used for high throughput assays for which it is necessary to isolate and investigate small bundles of particles and single particles.