Reconfigurable particle manipulation on micropillar-integrated silicon chips using a two-chip acoustofluidic platform

Reconfigurable acoustofluidic systems offer versatile and flexible capabilities for the capture, separation, and assembly of biological particles. However, conventional approaches generally require complex device architectures, high-precision micro-/nanofabrication, as well as sophisticated acoustic field control, resulting in increased fabrication costs and system complexity. Herein, we report a two-chip acoustofluidic platform that enables reconfigurable particle manipulation using a silicon chip integrated with micropillar arrays. Acoustic waves generated on the LiNbO₃ substrate are transmitted through a coupling medium to induce oscillations in the silicon superstrate and integrated micropillars, thereby generating localized secondary acoustic radiation forces that capture particles around the micropillars. We systematically investigated the effects of micropillar size, shape, spatial arrangement, and particle size on capture efficiency. The results indicate that particle capture efficiency is predominantly governed by the dimensions of the micropillars and particles, whereas the micropillar shape plays a negligible role. High-efficiency capture of 20-30 μm particles is achieved when micropillar diameters range from 200 to 500 μm, and the efficiency increases with higher input power. Moreover, by adjusting the layout of the micropillars, the arrangement of particles can be dynamically reconfigured to align with the micropillar pattern, highlighting the platform's potential for reconfigurable acoustic particle manipulation.