The joint Project B7 together with Prof. Selhuber-Unkel in the CRC1261 deals with the imaging of cells labelled with magnetic nanoparticles (MNP) for the characterization of bioscaffolds. The measurement principle involves the excitation of higher harmonic excitations of the MNP from a monofrequent magnetic field, due to their magnetic non-linearity.

Fig 1. Monofrequent magnetic excitation of magnetic nanoparticles leads to formation of higher harmonic excitations – multiple of the excitation frequency is present in the nanoparticle signal.

This higher harmonic is excited such that it coincides with the mechanical resonance of the sensor. This way, the magnetic signal of the MNP are measured and can be distinguished from the monofrequent magnetic excitation, which is at a lower frequency than the mechanical resonance of the sensor. Furthermore, the sensor is oriented such that the applied field is perpendicular to the plane of the sensor, yielding a high attenuation of the applied magnetic field due to a strong demagnetization factor. This way, small magnetic fields from the MNP can be measured even though very high fields are applied to excite the higher harmonic excitations.

Fig 2. The imaging system is investigated with respect to sensitivity, spatial resolution and temporal resolution. For one, this involves characterization of the MNP with respect to their frequency dependent magnetic properties at high fields. And second, the correct modelling of the imaging system is crucial, such that measured data is interpreted correctly and limitations of the system can be described accurately.

The imaging system is investigated with respect to sensitivity, spatial resolution and temporal resolution. For one, this involves characterization of the MNP with respect to their frequency dependent magnetic properties at high fields. And second, the correct modelling of the imaging system is crucial, such that measured data is interpreted correctly and limitations of the system can be described accurately.

Selected publication

Ron-Marco Friedrich, Sebastian Zabel, Andreas Galka, Nils Lukat, Jan-Martin Wagner, Christine Kirchhof, Eckhard Quandt, Jeffrey McCord, Christine Selhuber-Unkel, Michael Siniatchkin, Franz Faupel, Magnetic particle mapping using magnetoelectric sensors as an imaging modality, Sci. Rep. 9, 1 (2019)

Nils Lukat, Ron-Marco Friedrich, Benjamin Spetzler, Christine Kirchhof, Christine, Arndt, Lars Thormählen, Franz Faupel, Christine Selhuber-Unkel. Mapping of magnetic nanoparticles and cells using thin film magnetoelectric sensors based on the delta-E effect, Sensors & Actuators: A. Physical, accepted (2020)