TY  - JOUR
A1  - Engelmann, Ulrich M.
A1  - Simsek, Beril
A1  - Shalaby, Ahmed
A1  - Krause, Hans-Joachim
T1  - Key contributors to signal generation in frequency mixing magnetic detection (FMMD): an in silico study
JF  - Sensors
N2  - Frequency mixing magnetic detection (FMMD) is a sensitive and selective technique to detect magnetic nanoparticles (MNPs) serving as probes for binding biological targets. Its principle relies on the nonlinear magnetic relaxation dynamics of a particle ensemble interacting with a dual frequency external magnetic field. In order to increase its sensitivity, lower its limit of detection and overall improve its applicability in biosensing, matching combinations of external field parameters and internal particle properties are being sought to advance FMMD. In this study, we systematically probe the aforementioned interaction with coupled Néel–Brownian dynamic relaxation simulations to examine how key MNP properties as well as applied field parameters affect the frequency mixing signal generation. It is found that the core size of MNPs dominates their nonlinear magnetic response, with the strongest contributions from the largest particles. The drive field amplitude dominates the shape of the field-dependent response, whereas effective anisotropy and hydrodynamic size of the particles only weakly influence the signal generation in FMMD. For tailoring the MNP properties and parameters of the setup towards optimal FMMD signal generation, our findings suggest choosing large particles of core sizes dc > 25 nm nm with narrow size distributions (σ < 0.1) to minimize the required drive field amplitude. This allows potential improvements of FMMD as a stand-alone application, as well as advances in magnetic particle imaging, hyperthermia and magnetic immunoassays.
KW  - key performance indicators
KW  - magnetic biosensing
KW  - coupled Néel–Brownian relaxation dynamics
KW  - frequency mixing magnetic detection
KW  - magnetic relaxation
KW  - micromagnetic simulation
KW  - magnetic nanoparticles
Y1  - 2024
U6  - https://doi.org/10.3390/s24061945
SN  - 1424-8220
N1  - This article belongs to the Special Issue "Advances in Magnetic Sensors and Their Applications"
VL  - 24
IS  - 6
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Aliazizi, Fereshteh
A1  - Özsoylu, Dua
A1  - Bakhshi Sichani, Soroush
A1  - Khorshid, Mehran
A1  - Glorieux, Christ
A1  - Robbens, Johan
A1  - Schöning, Michael J.
A1  - Wagner, Patrick
T1  - Development and Calibration of a Microfluidic, Chip-Based Sensor System for Monitoring the Physical Properties of Water Samples in Aquacultures
JF  - Micromachines
N2  - In this work, we present a compact, bifunctional chip-based sensor setup that measures the temperature and electrical conductivity of water samples, including specimens from rivers and channels, aquaculture, and the Atlantic Ocean. For conductivity measurements, we utilize the impedance amplitude recorded via interdigitated electrode structures at a single triggering frequency. The results are well in line with data obtained using a calibrated reference instrument. The new setup holds for conductivity values spanning almost two orders of magnitude (river versus ocean water) without the need for equivalent circuit modelling. Temperature measurements were performed in four-point geometry with an on-chip platinum RTD (resistance temperature detector) in the temperature range between 2 °C and 40 °C, showing no hysteresis effects between warming and cooling cycles. Although the meander was not shielded against the liquid, the temperature calibration provided equivalent results to low conductive Milli-Q and highly conductive ocean water. The sensor is therefore suitable for inline and online monitoring purposes in recirculating aquaculture systems.
KW  - chip-based sensor setup
KW  - aquaculture
KW  - microfluidics
KW  - impedance spectroscopy
KW  - thermometry
KW  - electrical conductivity of liquids
Y1  - 2024
U6  - https://doi.org/10.3390/mi15060755
SN  - 2072-666X
N1  - This article belongs to the Special Issue "Multisensor Arrays"
N1  - Corresponding author: Michael J. Schöning
VL  - 15
IS  - 6
PB  - MDPI
CY  - Basel
ER  -