Bead magnetorelaxometry with an on-chip magnetoresistive sensor

Bjarke Thomas Dalslet, Christian Danvad Damsgaard, Marco Donolato, Maria Strømme, Mattias Strömberg, Peter Svedlindh, Mikkel Fougt Hansen

    Research output: Contribution to journalJournal articleResearchpeer-review


    Magnetorelaxometry measurements on suspensions of magnetic beads are demonstrated using a planar Hall effect sensor chip embedded in a microfluidic system. The alternating magnetic field used for magnetizing the beads is provided by the sensor bias current and the complex magnetic susceptibility spectra are recorded as the 2nd harmonic of the sensor response. The complex magnetic susceptibility signal appears when a magnetic bead suspension is injected, it scales with the bead concentration, and it follows the Cole-Cole expression for Brownian relaxation. The complex magnetic susceptibility signal resembles that from conventional magnetorelaxometry done on the same samples apart from an offset in Brownian relaxation frequency. The time dependence of the signal can be rationalized as originating from sedimented beads.
    Original languageEnglish
    JournalLab on a Chip
    Issue number2
    Pages (from-to)296-302
    Publication statusPublished - 2011

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