An electronically controlled acoustic tweezer was used to demonstrate two acoustic manipulation phenomena: superposition of Bessel functions to allow independent manipulation of multiple particles and the use of higher-order Bessel functions to trap particles in larger regions than is possible with first-order traps. The acoustic tweezers consist of a circular 64-element ultrasonic array operating at 2.35MHz which generates ultrasonic pressure fields in a millimeter-scale fluid-filled chamber. The manipulation capabilities were demonstrated experimentally with 45 and 90-lm-diameter polystyrene spheres. These capabilities bring the dexterity of acoustic tweezers substantially closer to that of optical tweezers.
Courtney, C. R. P., Demore, C. E. M., Wu, H., Grinenko, A., Wilcox, P. D., Cochran, S., & Drinkwater, B. W. (2014). Independent trapping and manipulation of microparticles using dexterous acoustic tweezers. Applied Physics Letters, 104(15), . https://doi.org/10.1063/1.4870489