(230ad) Label Free Size Separation Strategies for Polydisperse Vesicle Suspensions

Authors: 
Storslett, K. J., University of California Berkeley
Muller, S. J., University of California at Berkeley
Microfluidic devices can be used to separate suspensions of deformable particles with different intrinsic characteristics (e.g. size, deformability, and shape) with reasonable throughputs and without requiring external labeling to do so. Vesicles serve as a model for cells and using these suspensions to test microfluidic separation schemes provides insight into cell separation and isolation for diagnostic purposes as well as separation of suspended contaminants from drinking water1. Two schemes for separating deformable vesicle suspensions by size are discussed: size exclusion and inertial focusing. The size exclusion separation device makes use of a filter that prevents many of the larger vesicles from passing through. The filtrate is collected at one outlet and the larger vesicles are collected at a separate outlet. This device showed good size separation between the two collected suspensions. It also was able to reduce the polydispersity of the collected suspensions relative to the original vesicle suspension. The inertial separation device was based on a design studied by Di Carlo et al2. This design was modified for our suspension parameters and showed an ability to separate the suspension by size; however, the separated suspensionâ??s polydispersity was either unchanged or only reduced slightly relative to the starting polydispersity. The advantage of the inertial separation device relative to the size exclusion filter device was its greatly increased throughput. Ultimately, one may select a separation strategy based on the relative importance of high throughput versus reduced polydispersity. Future work includes investigating cascading separation schemes to further optimize the separation.

(1) Di Carlo, D. Lab Chip 2009, 9, 3038-3046.

(2) Di Carlo, D.; Edd, J. F.; Irimia, D.; Tompkins, R. G.; Toner, M. Anal. Chem. 2008, 80, 2204-2211.