Selective patterning of hybrid colloids via reconfigurable acoustic-dielectric field

Acoustophoresis and dielectrophoresis are frequently used for microscale particle and cell manipulation but are often used as two separate modalities. This article presents dynamic, selective patterning of micro- and nanoparticles using a reconfigurable surface acoustic wave microfluidic platform that integrates both acoustic radiation force (ARF) and dielectrophoretic (DEP) force using a single actuation/excitation modality. This platform enables frequency-based modulation of acoustic wave polarization to dynamically control the competition between the acoustohydrodynamic (AHD) regime and the electrohydrodynamic (EHD) regime without changes to device geometry or buffer conditions. This system's exceptional capability to selectively pattern different micro- and nanomaterials is demonstrated, which cannot be achieved with existing acoustophoresis or dielectrophoresis technologies alone. In particular, the utility of this platform is demonstrated in the selective patterning of live and dead mammalian cells with high reversibility and reproducibility, and in controlled interaction of cells with functionalized microparticles. Together, these results demonstrate the potential of the reconfigurable acoustofluidic platform where acoustic effects create a force landscape and dielectric effects define landscape occupancy, providing a flexible and reversible framework for diverse microscale self-organization applications.