Micro-Acoustic-Trap (µAT) for Microparticle Assembly in 3D

Abstract Acoustic tweezers facilitate the manipulation of objects using sound waves. With the current state of the technology one can only control mobility for a single or few microparticles. This article presents a state of the art system where an Acoustic Lens was used for developing a Micro-Acoustic Trap for microparticle assembly in 3D. The model particles, 2 micrometer diameter polystyrene beads in suspension, were driven via acoustic pressure to form a monolayer at wavelength-defined distances above the substrate defined by the focal point of an Acoustic Lens The transducer was driven at 89 MHz, mixed with 100 msec pulses at a repetition rate of 2Hz. Beyond a threshold drive amplitude sufficient to overcome Brownian motion, this led to 2D assembly of the microparticles into close-packed rafts greater than 80 micrometers across (∼5 wavelengths of the carrier wave and >40 particles across). This methodology was further extended to manipulation of live Dictyostelium discoideum amoebae. This approach therefore offers maneuverability in controlling or assembling micrometer-scale objects using continuous or pulsed focused acoustic radiation pressure.