Generating Spatially Complex Ultrasonic Standing Waves for Particle Manipulation

We present a method for generating 2D complex ultrasonic standing waves based on the decomposition of a predefined pressure field into plane waves. Setting the spatial distribution of the pressure field allows one to create point acoustic traps with the desired relative position in a plane. A device containing 12 ultrasonic transducers was built which allowed one to generate specific 2D ultrasonic standing waves. Shadowgraph visualization of the pressure field and particles captured by it was performed. The pressure distributions corresponded to the expected ones, and the positions of the trapped particles were consistent with the theoretical prediction.