3-D Acoustic Tweezers Using a 2-D Matrix Array With Time-Multiplexed Traps

The use of acoustic tweezers for precise manipulation of microparticles in the aqueous environment is essential and challenging for biomechanical applications in vivo. A 3-D acoustic tweezer is developed in this study for 3-D manipulation by using a two-dimensional (2-D) phased array consisting of 256 elements operating at 1.04 MHz. The emission phases of each element are iteratively determined by a backpropagation algorithm to generate multiple acoustic traps. Different traps are multiplexed in time, thus forming synthesized acoustic fields. We demonstrate the 3-D levitation and translation of positive acoustic contrast particles, a major class of bioparticles, in water by different acoustic traps, and compare the positional deviation along the intended path via experimentally measured trajectories. Improved manipulating stability was achieved by multiplexed acoustic traps. The 3-D acoustic tweezers proposed in this study provide a versatile approach of contactless bioparticle trapping and translation, paving the way toward future application of nanodroplet and microbubble manipulations.