Confinement and aggregation of colloidal particles in an ionic liquid microdroplet formed by optical tweezers

Abstract

Abstract Currently, there is considerable interest in applying colloidal assemblies to photonic and plasmonic devices. Optical tweezing enables the preparation of such assemblies at desired positions, but the assembly process occurs only in areas irradiated by laser light. Here, we demonstrate the collection and assembly of colloidal particles in areas beyond the irradiation area. The particles are taken into a microdroplet formed by optical tweezing in a thermo-responsive ionic liquid (IL)/water mixture. The confined particles aggregate as the droplet shrinks. The mechanism of confinement and aggregation of colloidal particles are discussed in view of the surface charge of the particles.