Restricted diffusion in soft materials and elsewhere
School of Physics Nonlinear Science & Mathematical Physics Series: Dr. John deBruyn, The University of Western Ontario
Diffusion is an important physical process in many systems, from gases to biological cells. In the simplest case, a diffusing particle undergoes a random walk and its mean squared displacement increases linearly with time. In many cases, however, the diffusion is not ideal: The motion of the diffusing species can be restricted in a variety of ways, leading to “sub-diffusion” in which the mean squared displacement increases more slowly. I will discuss experiments on the restricted diffusion of tracer particles in soft-matter systems close to a gel transition. Our experimental measurements provide information about the microstructure of the system and its evolution as the system gels on the bulk scale. Computer simulations help to clarify the interpretation of the data. I will also briefly discuss other systems in which restricted diffusion plays an important role.