Resonant ultrasonic particle manipulators and their applications in sensor systems

The paper describes the use of ultrasonic standing waves as bulk acoustic wave actuators, exploiting the acoustic radiation forces within the standing wave to move biological cells or other particles. This is a technology with the potential to enhance many forms of microflow-based sensors. Example applications discussed include half-wavelength filters, flow-through chambers which move cells from one fluid medium into another (washing the cells), and quarter wavelength chambers that attract cells to a solid boundary such as the face of a sensor. Microfabricated devices are described, including resonators with multiple sub-wavelength resonances, which are driven by multilayer thick film PZT actuators.