Probing the local environment in colloidal glass

We developed a method to probe the local environment in colloidal glass by measuring the rotational diffusion of elliptical tracer particles. Using tracers of various aspect ratios as passive micro-probes, we explored the response of the material to different local strains. Special design of the tracers enhances its optical anisotropy, which enables us to follow the 3-dimensional rotation of nearly spherical probes. We found as the volume fraction of the colloidal suspension approaches the glass transition point, the rotational diffusion of the ellipsoids slows down dramatically and differs significantly spatially, which reflects the heterogeneity of the local environment.