Fractionation of non-Brownian rod-like particle suspensions in a viscoplastic fluid

In this work we explore a fractionation technique for non-Brownian rod-like particle suspensions based upon the control of the threshold for motion in a yield stress fluid. The principle is demonstrated by observing the motion of particles under the influence of a centrifugal force in a weak gel. Here we develop calibration curves of the force required to initiate motion in a gel under numerous configurations of the particles. Demonstration separations of bidisperse suspensions are reported. Here we achieve complete separation of dilute suspensions based upon length, diameter, or density. The method is then applied to an industrially important suspension, that is a polydispersed papermaking fibre suspension, in which a length-based fractionation is reported.