Transport and clogging of fibers in millifluidic channels

The transport of particles in strongly confined geometries is a complex process, especially when the particle size becomes comparable to the channel size. An interplay of particle shape, hydrodynamics, and steric and colloidal forces can lead to clogged channels. In this work, we explore the transport and clogging of fibers in millifluidic channels using a combination of experiments, theory and computations. We quantify the clogging probability of a fiber when flowed through a bend as a function of fiber length, channel width, bend angle and wall curvature, which we translate to a geometric condition for clogging. Using numerical simulations based on resistive-force theory coupled to a frictional model for wall contact, we then map out a phase space of particle configurations and lengths that demarcate cases where the fiber is clogged, finding qualitative agreement with experiments. We then turn to more complex geometries such as constrictions to illustrate the role of fiber length relative to gap size and the curvature of the boundaries in inducing a clog. Put together, these insights build toward a mechanistic understanding of clogging and transport of anisotropic particles in porous media, and in developing guidelines for the design of clog-resilient fluid systems.