Engineering Soft Functional Materials: From Self-assembly to Field-assisted Assembly
University of Michigan
9 AM, Thursday, February 2nd, 2017
1065 Kemper Hall
Abstract: The ubiquity of self-assembly – the process of creating organizational order in systems of components – in nature has inspired technological developments towards synthetic building blocks that assemble into desirable structures with a unique set of properties. Isotropic spherical colloids are a simple example of such building blocks where their spatial arrangement yields photonic crystals that exhibit structural color. The key step towards engineering the assembly process is the ability to tune the interparticle interactions. However, the experimental realization of target structures can be challenging owing to the slow kinetics of the self-assembly process. There is a concerted effort in the field to identify the factors that impact the particle-particle interactions and control the assembly dynamics via external fields. What happens when shape or surface anisotropic particles are used as building blocks for assembly? How is the assembly in bulk different from the 2D assembly in the presence of a fluid interface? What interactions are induced in the presence of an external electric field? To address some of these questions, my research focuses on the assembly of shape and surface anisotropic colloidal particles. I present experiments on the application of fluid interfaces as a template for assembly and discuss the role of particle surface properties in tuning the mechanical stability and flow behavior of the assembled monolayer. External direct current fields are used to control the dynamics of assembly in dense colloidal suspensions and measurements of the electrophoretic mobility demonstrate the significance of the dispersion electrokinetic properties and suspension volume fraction. Given the need for generating shape-memory colloidal structures suitable for applications where rapid, on demand reconfiguration is required, I also present experiments on the actuation of dense suspension of surface anisotropic colloidal fibers using an external electric field. Insights obtained from all these studies contribute to our fundamental understanding of the principles central to the assembly processes and serve as a platform for engineering the bottom-up assembly of functional materials.
Biography: Sepideh Razavi received her PhD in chemical engineering from the City College of New York in 2015 where she worked with Prof. Ilona Kretzschmar on the assembly and flow behavior of colloidal particles at fluid interfaces. She is currently a postdoctoral fellow at University of Michigan working in Prof. Michael Solomon’s lab and her research focuses on the application of external fields to assemble anisotropic colloidal particles.