title: Lab-on-a-Chip Magneto-Immunoassays: How to Ensure Contact between Superparamagnetic Beads and the Sensor Surface.
abstract: Lab-on-a-chip immuno assays utilizing superparamagnetic beads as labels suffer from the fact that the majority of beads pass the sensing area without contacting the sensor surface. Different solutions, employing magnetic forces, ultrasonic standing waves, or hydrodynamic effects have been found over the past decades. The first category uses magnetic forces, created by on-chip conducting lines to attract beads towards the sensor surface. Modifications of the magnetic landscape allow for additional transport and separation of different bead species. The hydrodynamic approach uses changes in the channel geometry to enhance the capture volume. In acoustofluidics, ultrasonic standing waves force µm-sized particles onto a surface through radiation forces. As these approaches have their disadvantages, a new sensor concept that circumvents these problems is suggested. This concept is based on the granular giant magnetoresistance (GMR) effect that can be found in gels containing magnetic nanoparticles. The proposed design could be realized in the shape of paper-based test strips printed with gel-based GMR sensors.
authors.affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. beickenb@physik.uni-bielefeld.de.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Eickenberg
authors.affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. jmeyer@physik.uni-bielefeld.de.
authors.forename: Judith
authors.initials: J
authors.lastname: Meyer
authors.affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. lars@physik.uni-bielefeld.de.
authors.forename: Lars
authors.initials: L
authors.lastname: Helmich
authors.affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. dkappe@physik.uni-bielefeld.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kappe
authors.affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. aauge@physik.uni-bielefeld.de.
authors.forename: Alexander
authors.initials: A
authors.lastname: Auge
authors.affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. alexander_weddemann@hotmail.com.
authors.forename: Alexander
authors.initials: A
authors.lastname: Weddemann
authors.affiliation: Faculty of Arts and Sciences, Chemistry & Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA. wittbracht@fas.harvard.edu.
authors.forename: Frank
authors.initials: F
authors.lastname: Wittbracht
authors.affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. huetten@physik.uni-bielefeld.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hütten