title: Phase-changing sacrificial materials for interfacing microfluidics with ion-permeable membranes to create on-chip preconcentrators and electric field gradient focusing microchips.
abstract: We have developed a novel approach for interfacing ionically conductive membranes with microfluidic systems using phase-changing sacrificial layers. Imprinted microchannels in a polymer substrate are filled with a heated liquid that solidifies at room temperature, a monomer solution is placed over the protected channels and polymerized to form a rigid semipermeable copolymer, and then the protective layer is melted and removed, leaving an open microchannel interfaced with a polymer membrane. We have applied this method in miniaturizing electric field gradient focusing (EFGF) and carrying out on-chip protein preconcentration. A semipermeable copolymer in the EFGF microchips fills a region of changing cross-sectional area, which allows a gradient in electric field to be established when an electrical potential is applied. Our technique provides microchip EFGF devices that offer 3-fold improved resolution in protein focusing compared with capillary-based systems. In addition, these EFGF microchips can separate peptide samples with resolution similar to what is obtained in capillary electrophoresis microdevices, and the micro-EFGF systems enrich analytes by a factor of >150. Finally, we have fabricated membrane-integrated microfluidic devices that can concentrate protein samples (R-phycoerythrin) over 10 000-fold to facilitate microchip capillary electrophoresis. Interfacing microchannels with ion-permeable membranes has great potential to enhance microchip analysis of biomolecules.
authors.affiliation: Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602-5700, USA.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Kelly
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.forename: Adam T
authors.initials: AT
authors.lastname: Woolley
mesh_terms: D004553:Electric Conductivity; D019075:Electrophoresis, Capillary / Q000379:methods; D046209:Electrophoresis, Microchip / Q000379:methods*; D007477:Ions / Q000737:chemistry; D007525:Isoelectric Focusing / Q000379:methods*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D010455:Peptides / Q000032:analysis*; D010539:Permeability; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013696:Temperature; D013997:Time Factors
chemical_list: D007477:Ions; D010455:Peptides; D011108:Polymers