(6gl) Model Colloid System for the Direct Observation of Interfacial Sorption Kinetics

Particle adsorption to an interface can be a complicated process, motivating detailed measurements of the relevant factors that govern adsorption coverage and rates. My research uses micron-sized particles as an experimental model system to investigate the effect of particle characteristics on adsorption kinetics through direct observations at the individual particle level. The particle-interface interaction strength can be tuned to be comparable with nanoscale systems and experimental conditions can be carefully controlled through modifications to the particles and/or interface.  For instance, the effect of shape on adsorption kinetics is investigated by tracking colloidal dimers near a solid interface. Kinetics are measured by tracking transitions between an entropically trapped adsorbed state and a desorbed states driven by Brownian motion. The observed kinetics can be directly compared to theoretical predictions based on the measured interaction potential and local diffusivity. Multiple light microscopy methods are employed for 3-dimensional particle tracking, including total internal reflection microscopy (TIRM) for positions near the surface and off-focus tracking for positions in the bulk. This experiment approach can be extended to study complex adsorption processes in detail, including effects such as crowding, deformability, and applied fields.