(518g) Complex Fluid Clogging across Length Scales: From Cross-Linking Polymers, to Colloids, to Granular Media

Clogging can occur nearly anywhere: in the porous media of the earth, in industrial flows through hoppers, in water filters, 3D printing nozzles, and in some of the worst instances, in our arteries. These examples of clogging include clogs formed by colloidal particles, by granular media, and even by crosslinking polymers. Despite the differences in the type of complex fluid involved, some aspects of clogging are universal, like its stochastic nature and the importance of the constituent material properties. At the same time, understanding the nature of clogging is key to controlling or preventing it, and facilitates improved design of filters, hoppers, and even diagnostic tools. This talk explores pore clogging from the micron scale to the centimeter scale, investigating flows of several different types of complex fluids through small spaces. On the microfluidic scale, we study intermittent dynamics caused by polymers crosslinking in-situ as they flow. This model system might represent situations encountered in polymer flows in 3D printing applications, or, in a greatly simplified way, two of the steps in the coagulation cascade. In colloidal clogging of microfluidic pores, we study clogging of both rigid and soft colloids in a tapered pore geometry, to simultaneously investigate clogging by bridging and clogging by sieving. On the macro-scale, a quasi-2D hopper is used to investigate both jamming and avalanche flows in small-system mixtures of soft and rigid particles. In all cases, despite salient differences between the systems, we find the material properties of the complex fluid to govern flow behavior. In the examples of crosslinking polymers and granular media, intermittent dynamics are determined by the softness of the polymer gel or the granular particles. In colloidal pore clogging, however, adjusting particle softness can qualitatively change the types of clogs that form, from those which form continuously to those which form discontinuously. In all cases, our measurements reveal universal features in the stochastic nature of clogging.