title: Enhanced mixing in polyacrylamide gels containing embedded silica nanoparticles as internal electroosmotic pumps.
abstract: Many biosensors, including those based on sensing agents immobilized inside hydrogels, suffer from slow response dynamics due to mass transfer limitations. Here we present an internal pumping strategy to promote convective mixing inside crosslinked polymer gels. This is envisioned as a potential tool to enhance biosensor response dynamics. The method is based on electroosmotic flows driven by non-uniform, oscillating electric fields applied across a polyacrylamide gel that has been doped with charged colloidal silica inclusions. Evidence for enhanced mixing was obtained from florescence recovery after photobleaching (FRAP) measurements with fluorescein tracer dyes dissolved in the gel. Mixing rates in silica-laden gels under the action of the applied electric fields were more than an order of magnitude faster than either diffusion or electrophoretically driven mixing in gels that did not contain silica. The mixing enhancement was due in comparable parts to the electroosmotic pumping and to the increase in gel swelling caused by the presence of the silica inclusions. The latter had the effect of increasing tracer mobility in the silica-laden gels.
authors.affiliation: Center for Complex Fluids Engineering, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States.
authors.forename: Marvi A
authors.initials: MA
authors.lastname: Matos
authors.forename: Lee R
authors.initials: LR
authors.lastname: White
authors.forename: Robert D
authors.initials: RD
authors.lastname: Tilton
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D004058:Diffusion; D004560:Electricity; D053841:Electroosmosis / Q000295:instrumentation*; D036681:Fluorescence Recovery After Photobleaching; D053758:Nanoparticles / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; C016680:polyacrylamide gels; D012822:Silicon Dioxide