Colloidal Assembly and Separation under UV‐Induced Convective Flows and on Inclines

Abstract Achieving directed motility and separation of colloidal particles is a crucial requirement in a range of technological areas. Herein, we describe a system that exploits the photothermal properties of plasmonic nanoparticles for the assembly and separation of larger microparticles. Irradiating an aqueous suspension of gold or silver nanoparticles with UV light generates thermal convection which can be used to move and organize larger particles. Moving the UV light source allows the relocation of the particle cluster. In addition, thermal convection can be used to separate inert particles of different sizes on an inclined plane. Since fluid motion stems from thermal convection, collection and separation can be reversed simply by turning off the UV light enabling a rapid on‐demand response system.