Optimization of Transport-Driven Continuous SPLITT Fractionation

Abstract

Continuous SPLITT fractionation (CSF) utilizes various forces acting across the thin dimension of a ribbonlike flow channel or cell to segregate suspended particles and macromolecules into different flow laminae. One or more splitters at the outlet of the channel then divide the differentially populated laminae into two or more substreams. The separation is rapid because of the extreme thinness (usually <0.5 mm) of the cell. The throughput/cell volume ratio is high because of the high separation speed. The purpose of this paper is to examine factors affecting resolution, speed, and throughput in transport-based CSF. The time of separation is roughly proportional to the path length of separation, giving CSF a >10²-fold advantage over many conventional techniques like gravitational sedimentation. The resolving power of CSF is related to the ratio of inlet substream flow rates, making possible the direct control of resolution. A straightforward tradeoff is found between resolution and throughput. The throughput is shown to be proportional to the concentration of particles in the feed stream, to the field strength, to the mobility range that can be tolerated for incompletely resolved material, and to the SPLITT cell area. However, throughput is independent of cell thickness. Optimization considerations suggest the desirability of working with very thin cells of high area and thus a high aspect ratio in CSF.