Title: Characterizing dynamic pathways in colloidal self-assembly

Author (Invited): W. Benjamin Rogers, Brandeis University

Abstract:

Grafting DNA onto microscopic colloidal particles can `program' them with information that tells them exactly how to self-assemble. Recent advances in our understanding of how the specific interactions emerge due to DNA hybridization have enabled the assembly of a wide variety of crystal structures. However, the dynamic pathways by which these crystals self-assemble are largely unknown. In this talk I will present an experimental study of the nucleation and growth kinetics of colloidal crystals due to DNA hybridization. Specifically, I will describe a microfluidics-based approach in which we produce hundreds of monodisperse, isolated droplets filled with colloidal particles and then track the formation of crystals within each drop as a function of time. We find that the initial nucleation of crystals from a supersaturated solution involves overcoming a free-energy barrier, and that the height of this barrier decreases dramatically with decreasing temperature. We also find that once nucleated, the crystals grow at a rate that is limited by the diffusive flux of colloidal particles to the growing crystal surface. These findings may help us to devise new strategies to tune the nucleation rates and crystal growth kinetics independently, which will be helpful as we try to engineer higher quality or more complex self-assembled structures.