title: Nanocapillary array interconnects for gated analyte injections and electrophoretic separations in multilayer microfluidic architectures.
abstract: An electrokinetic injection technique is described which uses a nuclear track-etched nanocapillary array to inject sample plugs from one layer of a microfluidic device into another vertically separated layer for electrophoretic separations. Gated injection protocols for analyte separations, reported here, establish nanocapillary array interconnects as a route to multilevel microfluidic analytical designs. The hybrid nanofluidic/microfluidic gated injection protocol allows sample preparation and separation to be implemented in separate horizontal planes, thereby achieving multilayer integration. Repeated injections and separations of FITC-labeled arginine and tryptophan, using 200-nm pore-diameter capillary array injectors in place of traditional cross injectors are used to demonstrate gated injection with a bias configuration that uses relay switching of a single high-voltage source. Injection times as rapid as 0.3 s along with separation reproducibilities as low as 1% for FITC-labeled arginine exemplify the capability for fast, serial separations and analyses. Impedance analysis of the micro-/nanofluidic network is used to gain further insight into the mechanism by which this actively controlled nanofluidic-interconnect injection method works. Gated sample introduction via a nanocapillary array interconnect allows the injection and separation protocols to be optimized independently, thus realizing the versatility needed for real-world implementation of rapid, serial microchip analyses.
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Donald M
authors.initials: DM
authors.lastname: Cannon
authors.forename: Tzu-Chi
authors.initials: TC
authors.lastname: Kuo
authors.forename: Paul W
authors.initials: PW
authors.lastname: Bohn
authors.forename: Jonathan V
authors.initials: JV
authors.lastname: Sweedler
mesh_terms: D001120:Arginine / Q000737:chemistry / Q000302:isolation & purification*; D019075:Electrophoresis, Capillary / Q000295:instrumentation* / Q000379:methods; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D008904:Miniaturization; D036103:Nanotechnology / Q000295:instrumentation* / Q000379:methods; D014364:Tryptophan / Q000302:isolation & purification*
chemical_list: D005456:Fluorescent Dyes; D014364:Tryptophan; D001120:Arginine; D016650:Fluorescein-5-isothiocyanate