Particle focusing in a microfluidic channel with acoustic metamaterial

Particle focusing has been numerically studied in a microchannel filled by an acoustic metamaterial fluid that possesses negative density, and under a pair of ultrasound incidences from the lateral boundaries. Acoustic metamaterial with negative density exponentially damps the ultrasound field along its propagation direction that forms a very low field at the center of the microchannel. Driven by the acoustic radiation force and dissipated by the fluid, the particles laterally vibrate in the microchannel and gradually aggregated in the vicinity of the channel center. A structural microchannel with acoustic resonant elements that generates equivalent negative density property for the fluid in the microchannel has been designed, which decays the ultrasound field in a similar way. Particle movement in the structural microchannel has also been investigated and particle focusing is also achieved. The merit of the proposed particle focusing method by metamaterial concept lies in its independence on the type of the incident wave and width or size of the microchannel.