title: On-chip manipulation and detection of magnetic particles for functional biosensors.
abstract: We demonstrate the real-time on-chip detection and manipulation of single 1 microm superparamagnetic particles in solution, with the aim to develop a biosensor that can give information on biological function. Our chip-based sensor consists of micro-fabricated current wires and giant magneto resistance (GMR) sensors. The current wires serve to apply force on the particles as well as to magnetize the particles for on-chip detection. The sensitivity profile of the sensor was reconstructed by simultaneously measuring the sensor signal and the position of an individual particle crossing the sensor. A single-dipole model reproduces the measured sensitivity curve for a 1 microm bead. For a 2.8 microm bead the model shows deviations, which we attribute to the fact that the particle size becomes comparable to the sensor width. In the range between 1 and 10 particles, we observed a linear relationship between the number of beads and the sensor signal. The real-time detection and manipulation of individual particles opens the possibility to perform on-chip high-parallel single-particle assays.
authors.affiliation: Eindhoven University of Technology, Eindhoven, The Netherlands. x.j.a.janssen@tue.nl
authors.forename: X J A
authors.initials: XJ
authors.lastname: Janssen
authors.forename: L J
authors.initials: LJ
authors.lastname: van IJzendoorn
authors.forename: M W J
authors.initials: MW
authors.lastname: Prins
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D003198:Computer Simulation; D008280:Magnetics; D046208:Microchip Analytical Procedures / Q000379:methods*; D012680:Sensitivity and Specificity