Grant: Discovery Grants Program - Individual

How materials self-organize into ordered structures, and how they get stuck in disordered states are among the most profound problems in condensed matter and biophysics. Monodisperse colloids in suspension can be conceived of as ""big atoms"" to study these fundamental problems. Self-assembly in colloids closely mimics thermodynamic phase behavior in atomic fluids. Tunability of colloidal interactions allows one to ""tune"" the colloidal free energy: external fields can tune the energetic contributions to the free energy while size and shape polydispersity can be used to control the entropic contributions. New forms of experimental control lead to novel phenomena. In this proposal, complementary experimental techniques will be combined with an unprecedented control over interparticle interactions (via novel electric field geometries) and polydispersity to create novel equilibrium microscale and nanoscale colloidal structures, with applications in materials science and biophysics. Electric fields will be used as thermodynamic variables to traverse colloidal phase transitions, providing insights into fundamental non-equilibrium problems in condensed matter, such as the kinetics of crystallization and the glass transition. We are studying colloidal suspensions in novel electric field geometries as well as anisotropic liquid-crystalline media in order to achieve greater control over crystal formation and impurity defect suppression. This will allow us to obtain more detailed information about kinetics in rare, extremely quick or extremely slow processes (crystal nucleation, crystal growth and the glass transition). External fields also enable us to make new kinds of nano-patterned materials, with applications as magnetic films, photonic crystals or electrorheological fluids. Advances in this field will thus result in materials with improved functionality.