Chemical Engineering Seminar

There is an increasing need to engineer interfacial friction in technologies as diverse as soft robotics, virtual reality, and consumer products. The animal kingdom provides many examples of soft surfaces that can effectively control friction, even in extreme environments where high shear rates and complex fluids are found at the interface. This talk focuses on the solid and fluid mechanics principles that can explain frictional tribology when different fluids and heterogeneous patterns influence the interfacial mechanics of sliding. The first part of the talk focuses on colloidal suspension rheology when particle roughness is present. Rough colloids have interesting linear viscoelasticity and shear thickening physics that arise from rotational constraints between particles. Direct visualization from confocal rheometry, combined with mode coupling and hydrodynamic models, provide a compelling explanation based on excluded volume length scales. The second part of the talk investigates various ways of modifying the friction between elastomer and hydrogel surfaces, including the use of slip additives such as erucamide, incorporation of pattern geometry that mimic the finger ridges of humans and robots, and using dense colloidal suspensions as the continuum lubricating fluid. The long-term vision is to create new frontiers in haptic science through the interfacial design of colloidal and polymeric materials.