CONFERENCE C3M : Prof Safa Jamali (Northeastern University, USA)

Network science for understanding the physics and rheology of colloidal systems

Attractive colloidal particles in a simple fluid, depending on their packing fraction and interactions can exhibit a wide range of exotic rheological behavior. For instance, they can assemble into space spanning networks with mechanical properties of a viscoelastic solid, aka colloidal gels. Over the past couple of decades and owing to a tremendous advance in our experimental and computational capabilities, we have built an understanding of the complex dynamics that give rise to such physical and rheological behavior : rather than particle-scale micromechanics, it is the collective dynamics of the colloids at a coarser scale that control the macroscopic/bulk properties of a particulate system. Whether it’s a force network that carries the highest stresses in a shear thickening suspension, or a porous network of particles that gives a gel its elasticity, it is a “network” referring to the collective particle dynamic/behavior that is responsible for the physical characteristics of a system. Thus, understanding the physics of this particulate network is the key to controlling and designing particulate systems with desirable properties. I will discuss how borrowing well-established concepts from network science can help us interrogate and characterize these particulate networks and build a coarse-grained description of the system. These mesoscale structures, identified through community detection techniques that are commonly used in social or economic networks, provide a new understanding of physics and rheology in attractive colloidal gels. Finally, I will discuss some of the unexplored avenues and potential directions that these new techniques can make an impact in.