Dynamics and Rheology of Colloidal Rod Suspensions Measured with Differential Dynamic Microscopy

Dynamics and Rheology of Colloidal Rod Suspensions Measured with Differential Dynamic Microscopy

Colloidal rod suspensions form a variety of structures and form arrested phases at relatively low volume fractions.These properties make them excellent rheological modifiers and useful as model systems to understand complex systems like networks of biopolymer filaments. Both macro- and micro-rheology methods have characterized rod suspensions and gels.Here,we use a relatively new microrheology technique, differential dynamic microscopy (DDM), which combines elements of video microscopy and dynamic light scattering. With DDM we explore how the time scale of density fluctuations, form of the intermediate scattering function, and non-ergodicity parameter scale with both rod volume fraction and aspect ratio. Further, we compare our DDM microrheology with macroscopic bulk rheology in order to make connections between microscale dynamics and bulk mechanical properties; connections have been built for colloidal spherical suspension, but are more challenging to make with anisotropic particles.