title: Tunable membranes for free-flow zone electrophoresis in PDMS microchip using guided self-assembly of silica microbeads.
abstract: In this paper, we evaluate the strategy of using self-assembled microbeads to build a robust and tunable membrane for free-flow zone electrophoresis in a PDMS microfluidic chip. To fabricate a porous membrane as a salt bridge for free-flow zone electrophoresis, we used silica or polystyrene microbeads between 3-6 μm in diameter and packed them inside a microchannel. After complete evaporation, we infiltrated the porous microbead structure with a positively or negatively charged hydrogel to modify its surface charge polarity. Using this device, we demonstrated binary sorting (separation of positive and negative species at a given pH) of peptides and dyes in standard buffer systems without using sheath flows. The sample loss during sorting could be minimized by using ion selectivity of hydrogel-infiltrated microbead membranes. Our fabrication method enables building a robust membrane for pressure-driven free-flow zone electrophoresis with tunable pore size as well as surface charge polarity.
authors.affiliation: Department of Electrical Engineering and Computer Science, ‡Department of Biological Engineering, §Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, MA 02139, United States.
authors.forename: Yong-Ak
authors.initials: YA
authors.lastname: Song
authors.forename: Lidan
authors.initials: L
authors.lastname: Wu
authors.forename: Steven R
authors.initials: SR
authors.lastname: Tannenbaum
authors.forename: John S
authors.initials: JS
authors.lastname: Wishnok
authors.forename: Jongyoon
authors.initials: J
authors.lastname: Han
mesh_terms: D004129:Dimethylpolysiloxanes; D004586:Electrophoresis / Q000379:methods*; D057446:Hydrodynamics; D008567:Membranes, Artificial; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D008863:Microspheres; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D004129:Dimethylpolysiloxanes; D008567:Membranes, Artificial; C013830:baysilon; D012822:Silicon Dioxide