TY  - JOUR
A1  - Engelmann, Ulrich M.
A1  - Pourshahidi, Mohammad Ali
A1  - Shalaby, Ahmed
A1  - Krause, Hans-Joachim
T1  - Probing particle size dependency of frequency mixing magnetic detection with dynamic relaxation simulation
JF  - Journal of Magnetism and Magnetic Materials
N2  - Biomedical applications of magnetic nanoparticles (MNP) fundamentally rely on the particles’ magnetic relaxation as a response to an alternating magnetic field. The magnetic relaxation complexly depends on the interplay of MNP magnetic and physical properties with the applied field parameters. It is commonly accepted that particle core size is a major contributor to signal generation in all the above applications, however, most MNP samples comprise broad distribution spanning  nm and more. Therefore, precise knowledge of the exact contribution of individual core sizes to signal generation is desired for optimal MNP design generally for each application. Specifically, we present a magnetic relaxation simulation-driven analysis of experimental frequency mixing magnetic detection (FMMD) for biosensing to quantify the contributions of individual core size fractions towards signal generation. Applying our method to two different experimental MNP systems, we found the most dominant contributions from approx. 20 nm sized particles in the two independent MNP systems. Additional comparison between freely suspended and immobilized MNP also reveals insight in the MNP microstructure, allowing to use FMMD for MNP characterization, as well as to further fine-tune its applicability in biosensing.
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.jmmm.2022.169965
SN  - 0304-8853
VL  - 563
IS  - In progress, Art. No. 169965
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Pourshahidi, Ali Mohammad
A1  - Achtsnicht, Stefan
A1  - Offenhäusser, Andreas
A1  - Krause, Hans-Joachim
ED  - Offenhäusser, Andreas
T1  - Frequency Mixing Magnetic Detection Setup Employing Permanent Ring Magnets as a Static Offset Field Source
JF  - Sensors
N2  - Frequency mixing magnetic detection (FMMD) has been explored for its applications in fields of magnetic biosensing, multiplex detection of magnetic nanoparticles (MNP) and the determination of core size distribution of MNP samples. Such applications rely on the application of a static offset magnetic field, which is generated traditionally with an electromagnet. Such a setup requires a current source, as well as passive or active cooling strategies, which directly sets a limitation based on the portability aspect that is desired for point of care (POC) monitoring applications. In this work, a measurement head is introduced that involves the utilization of two ring-shaped permanent magnets to generate a static offset magnetic field. A steel cylinder in the ring bores homogenizes the field. By variation of the distance between the ring magnets and of the thickness of the steel cylinder, the magnitude of the magnetic field at the sample position can be adjusted. Furthermore, the measurement setup is compared to the electromagnet offset module based on measured signals and temperature behavior.
KW  - magnetic sensors
KW  - biosensors
KW  - frequency mixing magnetic detection
KW  - magnetic nanoparticles
Y1  - 2022
U6  - http://dx.doi.org/10.3390/s22228776
SN  - 1424-8220
VL  - 22
IS  - 22
PB  - MDPI
CY  - Basel
ER  -