There are many techniques that can be used to self-assemble colloidal suspensions, such as Langmuir-Blodgett technique, sedimentation, evaporation, and centrifugation. These methods have been shown to successfully create static ordered structures such as colloidal cyrstals. While these methods create ordered structures, they lack the ability to be reconfigured to change the systems optical capabilities (e.g. diffraction of light from the colloidal crystal). By using directed self-assembly methods, colloidal suspensions can be assembled in a manner that is dynamic and allows for multiple manipulations of the particles in solution, in turn, creating a system with multiple optical capabilities. Alternating current (AC) electric field directed self-assembly is one such method that can be used to obtain this degree of tunability. By using AC electric fields, particle location and orientation can be controlled based on the electric field conditions (frequency and voltage), particle permittivity and size, solvent permittivity, and electrode design. Here we focus on assemblies with 3D electrodes and particles with properties for desired interactions with electromagnetic radiation. Current work is focused on using cylindrical post electrode designs to assemble dielectric microparticles (SiO2, TiO2, and PMMA) into patterns based on the post size and spacing. When the same electric field conditions are applied to each of these particle solutions, they are assembled into different locations and structures based on their differing permittivities. While these unary particle systems alone can create interesting patterns and particle organizations, the tunability of the system can be further increased by combining particle populations together. Binary colloidal suspensions (SiO2 and TiO2, TiO2 and PMMA, PMMA and SiO2) can elicit a slightly different response than their individual assembly results and can create an even more dynamic assembly. Since all of these systems are spatially controllable and reconfigurable, they are of interest for realizing tunable metamaterials and functional optical devices, such as metamaterial absorbers and radiative cooling devices, respectively.

Alternating current electric field driven assembly of colloidal suspensions using 3D features

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.