Centrifugal microfluidics for size-selective separation of polydisperse Mie-resonant silicon nanoparticles

Abstract

Microfluidic separation, based on sedimentation in curved channels under the action of centrifugal forces, is a powerful method for sorting nanoparticles. However, most studies demonstrate performance on model monodisperse polystyrene spheres. In this work, we implement a centrifugal microfluidic chip for a centrifuge, the parameters of which are calculated based on an existing theoretical model, to solve the practical problem of separating colloidal solutions of silicon nanoparticles (Si NPs) containing Mie-resonant Si NPs synthesized by laser ablation in liquid. We demonstrate efficient separation of the ablated colloidal solution of Si NPs (size range from 50 nm to 450 μm), leading to a significant narrowing of the nanoparticle size distribution in the outlet fractions. A key result is the successful separation of Si NPs possessing strong Mie-resonances in the visible spectrum, corresponding to diameters of approximately 120–240 nm. Thus, the presented approach demonstrates the potential of centrifugal microfluidics as an effective method for separation of polydisperse nanomaterials, in particular, Si NPs with resonant optical properties.