Acoustofluidics has emerged as a promising method for submicron particle manipulation. However, ultrahigh-frequency or focused sound waves are usually required to generate sufficient acoustic radiation force or localized streaming vortex for trapping nanoscale objects, which is more challenging in device fabrication. This work presents a novel method using a low-frequency acoustic field actuated micro-pillar array (APA) chip to efficiently enable programmable and parallel trapping of nanoparticles. Driven by the acoustic waves, each arrayed vibrating micropillar generates a highly localized acoustic field with enhanced acoustic radiation forces and well-confined vortex streaming around the pillar. The APA chip is demonstrated with geometric tuning ability of regulating the trapping limit by altering the pillar size. Micropillar arrays with a diameter of 5 µm are demonstrated to trap 112 nm particles efficiently. Thanks to the convenience of using ultrasounds and arraying micropillars of different geometric sizes, the APA chip provides an alternative of submicron particle manipulation technique for programmable and high-throughput trapping and patterning of particles, with potential for “lab-on-a-chip” sample preparations.
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