On-chip manipulation and detection of magnetic particles for functional biosensors

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We demonstrate the real-time on-chip detection and manipulation of single 1 µm 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 µm bead. For a 2.8 µm 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
Original languageEnglish
Pages (from-to)833-838
Number of pages6
JournalBiosensors and Bioelectronics
Issue number6
Publication statusPublished - 2008


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