CAREER: In- and Out-of-Equilibrium Behavior of Colloidal Clusters with Broken Symmetries

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Colloidal dispersions play an important role in materials processing for industries ranging from electronics to pharmaceuticals. When colloidal particles are organized into arrays and other structures, the resulting materials can exhibit optical and electrical properties that are not found in natural materials. Therefore, colloids serve as building blocks for fabricating advanced functional materials. This project will develop new approaches to make clusters of colloidal particles with well-controlled compositions and geometries, which will expand the range of materials that can be fabricated. The project will investigate how external fields can be used to manipulate the assembly of particles into clusters and ultimately into large ensembles. Results from the project will provide fundamental knowledge that scientists and engineers can use to develop materials and devices, such as new sensors or new coatings with controlled optical properties. In addition, the project team will develop a summer research program in colloidal science targeted to high school students in the Denver area and especially to students from underrepresented groups. A multi-disciplinary course titled "Engineering of Soft Materials" will be developed to engage undergraduate students in colloidal science and train them for careers in the materials industry. New approaches will be developed to make clusters of colloids with well-controlled broken symmetries. A microfluidic device that integrates both electric (for assembly) and optical fields (for structural cross-linking) will be used to fabricate monodisperse higher order colloidal clusters with addressable compositions and geometries. The asymmetric properties of colloidal clusters will be systematically studied within the context of particle propulsion, which constitutes a significant step toward understanding the transport properties of active colloids. A virtually patterned electrode will be used to generate micro-gradients in electric field and direct particles into periodic structures with addressable symmetry at both cluster and lattice levels. The coupled optical effects between neighboring clusters and the feasibility for making functional coatings will also be explored. The overall goal of the project is to understand how the broken-symmetry in colloidal clusters affects their in- and out-of-equilibrium behavior from the level of an individual particle to a large ensemble.