MEMS/MatSci Seminar: "Material friction at the microscale and its effects on soft materials"

Abstract: The need to engineer friction at the microscale is increasingly important in technologies as diverse as soft robotics and consumer products. In this seminar, I will describe our journey from the field of particulate materials to the realm of touch engineering. The first part of the talk focuses on the role of particle roughness in the rheology, structure, and dynamics of dense colloidal suspensions. We find that shear thickening, exemplified by the ability to run on cornstarch pools, is strongly affected by the particle shape and jamming distance. Experiments on our confocal rheometer reveal how different types of particles form different contact microstructures that give rise to viscous flows. The second part of the talk will focus on our work on haptic materials where we investigate how compression and bending of textures affect friction. A new model based on lubrication analysis predicts the sliding friction for patterned surfaces of many materials, such as elastomers, thermosets, and hydrogels in sliding conditions. The data are in excellent agreement with that collected from a bioinspired robotic fingertip and human fingers. This framework provides a foundation that informs the engineering of manufactured surfaces and automated systems, and furthermore enables the design of friction in realistic environments.