Soft materials, such as slurries, pastes, foams and emulsion, are ubiquitous in the chemical industries. These materials often behave as solids when left to themselves, but will flow-like a liquid when a sufficiently large stress is applied. Understanding the yielding and flow of soft materials is of crucial importance during industrial processing and handling of these materials, as well as for applications where the plasticity of a material is a feature to be controlled. While there is empirical knowledge about specific materials, little is known about the generic physical principles underlying their flow properties ("rheology") and how to predict these from knowledge of material composition. This project aims to better understand the relation between microscopic structure and macroscopic response to stress by fast three-dimensional imaging of well-characterized colloidal systems under controlled flow. The simultaneous measurements of the microstructure and the stress-strain state of these materials will allow us to identify generic microscopic features in the flow of dense suspensions, and therefore provide a better overall understanding of the rheology of this class of materials. This work is in collaboration with the group of Wilson Poon and Rut Besseling at the University of Edinburgh, UK. The two groups have extensive but complementary expertise in working with model soft materials such as colloidal pastes, colloidal gels, and emulsions. Personnel from each group will spend extended periods of time working directly with the other group, which will prepare them well for future interdisciplinary and international teamwork.
