Acoustic interference lens for trapping micro-scale particles

Acoustic trapping allows for the contactless manipulation of microparticles. It has led to many applications in chemistry, biology and engineering. In this paper, we report an acoustic cylindrical lens capable of modulating an ultrasound-dark field with minimal acoustic intensity in the center by interference. The ultrasound field, radiation force field and the flow field containing particles in the presence of the lens is simulated. Both simulation and experimental results confirmed that the ultrasound radiation field can be spatially modulated and trap small objects that are perpendicular to the direction of propagation of the ultrasonic waves, owing to the acoustic radiation forces in the system. This acoustic cylindrical lens has a simple structure and the potential to be used in vivo.