Multiscale Particle Separation through Interfacial and Multiphysics Control.

Particle separation supports the analysis and manufacture of biological and synthetic particulate materials, but the governing transport mechanisms and performance constraints change markedly from nanometer to millimeter scales. Methods used at different scales are commonly evaluated with different terminology and performance priorities, complicating direct comparison. This Review develops a cross-scale framework organized around nanoscale fractionation, microscale sorting, and macroscale classification. Nanoscale fractionation combines centrifugal migration, Brownian diffusion, pore access, and membrane retention. Channel confinement, hydrodynamic migration, applied fields, and signal-triggered actuation control microscale trajectories, whereas particle-fluid motion and aperture passage establish population-level cuts at larger processing scales. Across these regimes, method selection depends on particle size, density, shape, deformability, surface chemistry, concentration, and intended output. The comparison reveals how concentration, agglomeration, carrier-phase properties, and collection conditions alter the usable separation contrast and the balance among resolution, recovery, throughput, and particle integrity. Tunable interfaces, coupled fields, and scalable parallelization emerge as practical routes for extending operating windows while preserving selectivity during particle processing.