Our research focuses on measuring and manipulating colloidal and macromolecular interactions, dynamics, and structures in interfacial and confined geometries. This has broad relevance to traditional complex fluid applications (coatings, ceramics) as well as emerging nano- and micro- technologies related to fabrication of materials and devices (photonic, metamaterials, biological). The objective is to develop experimental and analytical tools to rationally manipulate material properties and dynamic processes with explicit consideration of thermodynamic and kinetic factors inherent to the colloidal domain. In our group, colloidal interactions are measured with exquisite sensitivity by monitoring equilibrium and non-equilibrium structures using optical microscopy and scattering methods. To interpret and predict the control parameters in interfacial colloidal systems, we have employed analytical and simulation techniques to rigorously model many-body, low Reynolds number hydrodynamics and particle interactions on the order of kT.
Within this broad framework, we have several immediate areas of interest. We are developing novel combinations of total internal reflection, video, and confocal microscopy techniques to allow direct, real space measurement of three dimensional colloidal trajectories in interfacial ensembles. These methods are being used to investigate: (1) feedback control of colloidal assembly processes to create defect free ordered materials (e.g., photonic materials), (2) the use of colloids as nonintrusive ultra-senstive probes of biomolecular interactions (e.g., drug delivery), (3) the use of colloidal components in reconfigurable electromagnetic materials and devices (e.g., antennas), and (4) the interactions and transport of colloidal particles in the environment (e.g., porous media). Our approach is based on a stepwise escalation of experimental and analytical complexity from single-particle/wall problems to multi-particle/multi-dimensional problems, which provides a foundation for understanding increasingly complex interfacial colloidal and macromolecular systems.
- Development of dynamic simulations and models of interfacial and confined colloidal systems.
- Measurement of multi-body & multi-dimensional interfacial colloidal forces and hydrodynamics.
- Diffusing colloidal probe measurements of energy and diffusivity landscapes.
- Interfacial colloidal self assembly mediated by reversibly tunable kT-scale interactions.
- Transient colloidal directed assembly processes using external applied fields.
- Bulk and interfacial phase behavior in the presence of tunable kT-scale interactions.
- Equilibrium & non-equilibrium colloidal structure characterization and manipulation.
- Protein, carbohydrate, and synthetic macromolecule interactions interrogated using nanoparticle probes.