UNS: Employing hydrodynamic lift and particle trajectory ratcheting to achieve sieve-free separations based on size and shape in cross-flow filtration

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1505795(Koch)The focus of the proposed research is to study particle transport phenomena that occur during cross-flow filtration of suspensions. In addition to development of fundamental understanding of these phenomena, the objective is to aid the development of a so-called sieve-free filtration system. While the proposed work is highly fundamental, engineering applications are its motivation.This is a proposal to conduct a combined theoretical/numerical/experimental study of particle separation in crossflow. The motivation for this study is to improve practices in cross-flow filtration - a high throughput method of separating particles (including cells or macromolecules) from a fluid and from smaller sized particles. In conventional operation, the separation is accomplished by sieving through a membrane with a small pore size. The PI argues, and the panel agreed that this is worth exploring, that an operation in which the separation is accomplished using particulate hydrodynamic transport processes rather than membrane exclusion would have the advantages of decreasing membrane fouling and improving the selectivity of the separation. Because of the high shear rates accessible in cross-flow filtration, inertial lift can keep the particles away from the coarse non-sieving membrane. In addition, a new sieve-free separation mechanism based on the ratcheting of particle trajectories at the rough surface of the membrane due to excluded volume interactions of the particle with the membrane will be investigated. The goal is to develop a predictive model for lift-based cross-flow, allowing separation based on shape as well as size and identifying the maximum filtration flux and particle concentration at which particles can be retained. This mechanism can lead to sieve-free separations of nanoparticles or proteins which are too small to separate based on hydrodynamic lift. The models developed will be tested and the reliability of sieve-free filtration demonstrated by experimental measurements of separation of micro- and nano-particles of well controlled size and shape in a Couette cell filter. In addition to graduate education, plans to reach out to K-12 students and by an experimental demonstration to be used in activities at the local children's museum and the Ithaca Science Center are laid out.