(125a) From Capture of Flowing Particles at Heterogeneous Surfaces to the Impact of Particle Shape

The interactions of particles with surfaces in flow is critical in assembly, separations, polishing processes, and in bioadhesion, for instance bacterial cell arrest leading to film formation. Here, we explore capture and near-surface motion of flowing particles based on a combination of surface and hydrodynamic interactions. DLVO-based descriptions of surface forces are typically understood in terms of average surface properties, making it impossible to anticipate important behaviors such as the distinction between particle arrest, rolling, or slipping. Further because the contact or interactive area between a particle and a surface is finite, measurements of average surface properties (density of chemical functionality, roughness, zeta potential) can miss interactive features even without hydrodynamic interactions. This talk will discuss how incorporation of nanoscopic electrostatic patchiness in flowing particulate systems produces unanticipated interactive and dynamic features. These include attractive particle-surface interactions and capture in systems where uniform electrostatic interactions of the same overall average charge density should be stabilizing, regimes of particle rolling-slipping-arrest, curvature- and size-dependence of capture and dynamic behaviors, and difference in behaviors depending on whether functionality is placed on an immobile wall or a flowing particle. Translating some of these concepts to complex current problems, we discuss capture and orientation of rod shaped particles and capsular bacteria. Jeff Davis was an energetic and inspiring collaborator in developing concepts and advancing much of this work. I hope to honor his memory with future rewarding collaborations at the interface of hydrodynamic and material interactions.