title: Isoelectric focusing in a poly(dimethylsiloxane) microfluidic chip.
abstract: This paper reports the application of ampholyte-based isoelectric focusing in poly(dimethylsiloxane) (PDMS) using methylcellulose (MC) to reduce electroosmosis and peak drift. Although the characteristics of PDMS make it possible to fabricate microfluidic chips using soft lithography, unstable electroosmotic flow (EOF) and cathodic drift are significant problems when this medium is used. This paper demonstrates that EOF is greatly reduced in PDMS by applying a dynamic coat of MC to the channel walls and that higher concentrations of MC can be used to increase the viscosity of the electrode solutions in order to suppress pH gradient drift and reduce "compression"of the pH gradient. To illustrate the effect of MC on performance, several fluorescent proteins were focused in microchip channels 5 microm deep by 300 microm wide by 2 cm long in 3-10 min using broad-range ampholytes at electric field strengths ranging from 25 to 100 V/cm.
authors.affiliation: Department of Chemical Engineering, and School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164, USA.
authors.forename: Huanchun
authors.initials: H
authors.lastname: Cui
authors.forename: Keisuke
authors.initials: K
authors.lastname: Horiuchi
authors.forename: Prashanta
authors.initials: P
authors.lastname: Dutta
authors.forename: Cornelius F
authors.initials: CF
authors.lastname: Ivory
mesh_terms: D000665:Ampholyte Mixtures / Q000737:chemistry; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D004560:Electricity; D053841:Electroosmosis; D046209:Electrophoresis, Microchip / Q000295:instrumentation / Q000379:methods*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D007525:Isoelectric Focusing / Q000295:instrumentation* / Q000379:methods; D008164:Luminescent Proteins / Q000737:chemistry; D008747:Methylcellulose / Q000737:chemistry; D010798:Phycocyanin / Q000737:chemistry; D010799:Phycoerythrin / Q000737:chemistry; D012828:Silicones / Q000737:chemistry*; D055672:Static Electricity; D013696:Temperature; D014783:Viscosity
chemical_list: D000665:Ampholyte Mixtures; D004129:Dimethylpolysiloxanes; D008164:Luminescent Proteins; D012828:Silicones; C002497:allophycocyanin; D010798:Phycocyanin; D010799:Phycoerythrin; D049452:Green Fluorescent Proteins; C013830:baysilon; D008747:Methylcellulose