Continuous size-based sorting of microparticles using reconfigurable scanning-optical-trap arrays

The continuous, high-precision sorting of microparticles by size is crucial for biomedical and materials science, yet achieving label-free operation, dynamic reconfigurability, and high throughput simultaneously remains challenging. Here, we demonstrate continuous, size-based sorting using reconfigurable scanning-optical-trap (SOT) arrays. The method employs a dynamic optical potential landscape of orthogonally arranged guiding and sorting tracks, created via high-speed laser scanning. Sorting is governed by a tunable “sorting gap” at track junctions, in which size-dependent optical forces deterministically route a particle onto a sorting track only if its diameter exceeds a gap-specific critical value. Simulations establish a predictive one-to-one particle-size-to-optimal-gap relationship. Experimentally, the system achieves a sorting resolution of 90%, an average accuracy >90% (peak 98% at 1000 Hz) within a 900 to 1100 Hz frequency window, and successfully performs the simultaneous, continuous sorting of a four-component polydisperse mixture. This reconfigurable, flow-free, and label-free method bridges precise optical manipulation with higher-throughput sorting, offering a versatile platform for analyzing complex colloidal and biological samples.