UC Santa Cruz

The integration of surface acoustic wave (SAW) technology with Lab-on-a-Chip (LOC) devices has enabled powerful acoustic mechanisms for cell sorting, cell deflection, and other types of manipulation of biological specimen. Their control can be further enhanced and specialized with the integration of phononic crystals, which are materials designed to have phononic bandgaps to control the propagation of acoustic waves through a substrate. While many methods of designing phononic crystals require fabrication techniques that alter the surface topology with pillar or hole arrays, our electropoling technique creates a completely monolithic substrate. Electropoling involves using a strong electric field to reverse the domains of a piezoelectric substrate in a periodic pattern to generate a phononic bandgap. The technique is both simple and allows for compatibility with microfluidic components. By integrating phononic crystal substrates into a LOC device, we can enable a new degree of control to SAW particle manipulation. Here we demonstrate the use of phononic crystals to reflect SAWs in order to generate standing SAW fields. Particle focusing experiments are performed to observe the standing wave pattern. This is a novel demonstration of utilizing reflecting phononic energy towards a functional device, as well as integration of phononic crystal technology into a microfluidic system device.