Controlling Extrudate Volume Fraction through Poroelastic Extrusion of Entangled Fibers

Abstract Many materials systems consist of mixtures of particles of various shapes, and readily deform and flow. For example, when a suspension of spherical or near-spherical particles passes through a constriction the volume fraction either remains the same or decreases. In contrast to these particle suspensions, here we observe that an entangled fiber suspension increases its volume fraction up to 14-fold after passing through a constriction. We attribute this response to the entanglements among the fibers that allows the network to move faster than the liquid. By changing the fiber geometry, we find that the entanglements originate from interlocking shapes or high flexibility. A quantitative poroelastic model is used to explain the increase in velocity and extrudate volume fractions. These results provide a new strategy to control soft materials, e.g., suspension concentration and porosity, during delivery, as occurs in healthcare, three-dimensional printing, or material repair.