CMOS compatible GHz ultrasonic Fresnel microfluidic actuator

Abstract

We report on an aluminum nitride based gigahertz frequency ultrasonic transducer to realize a microfluidic actuator using acoustic radiation force and acoustic streaming. The transducer uses focusing transducers placed in a Fresnel lens configuration, which generates bulk acoustic waves through the silicon substrate adding in phase at the focus. The transducer is planar and is fabricated with a CMOS compatible process, with no thin-film release steps. Peak displacement of 250pm was achieved at the focus with 1.06GHz and 5V amplitude input. Acoustic vortices were formed with microfluidic streaming velocity >2.6mm/s in water droplets placed on top of the transducer.