Acousto-dielectrophoretic enhancement enables label-free ternary separation of submicrometer particles

Label-free separation of multiple micrometer and submicrometer particle populations from complex samples is a critical but elusive capability. We report an integrated acousto-dielectric chip in which the piezoelectric potential associated with tilted-angle standing surface acoustic waves changes the local electric field distribution, thereby increasing the electric field gradient and enhancing dielectrophoretic forces. When combined with acoustic radiation forces in a cascaded geometry, this enhancement enables three distinct, size-governed particle migration modes in a single device. As a proof of concept, we demonstrate continuous-flow separation of 1.0, 0.4, and 0.25 μm radius polystyrene microspheres with removal efficiencies reaching 99.9% for the largest particles and purities of 87.8% and 97.1% for the two smaller fractions. As the underlying mechanism, piezoelectric modulation of the electric field gradient provides a low-voltage, high-resolution strategy for multi-target sorting of nanoscale bioparticles.