IBI: Magneto Mechanical Resonators

Magneto-Mechanical Resonators

In an idealized form, MMRs consist of two permanent magnets: a stator firmly connected to the housing and a rotator that can rotate axially with one degree of freedom. The interaction between the two magnets is governed by the magnetic dipole-dipole interaction. In a state of equilibrium, the magnets are aligned antiparallel, and they attract each other. The presence of a filament serves to maintain a specific distance between the magnets. An external magnetic field can be utilized to perturb the system out of a state of equilibrium, into which the system reverts through a damped oscillatory motion, the oscillation frequency of which is determined by the spatial separation between the magnets.

The minimally invasive approach has revolutionized surgical care by significantly reducing postoperative pain, recovery time, and hospital stay durations while improving cosmetic outcomes and overall cost-effectiveness. Society benefits from lower healthcare costs due to patients' quick recovery, fewer inpatient procedures, and reduced complications. Image-guided minimally invasive procedures are pivotal, especially in endovascular interventions by cardiologists and vascular surgeons, where precise navigation using guidewires and catheters is crucial. Traditional X-ray imaging, however, exposes patients and staff to radiation. A recently developed passive, wireless sensor, known as a magneto-mechanical resonator (MMR), offers a novel method for continuous position and orientation determination without radiation while also capturing physiological data. These submillimeter-sized permanent magnets can be integrated into medical instruments or used as passive implants for monitoring chemical properties and chronic diseases like diabetes. The MMR technology's low complexity and scalability make it economically appealing, especially in developing countries with limited access to vascular interventions.

Our research group focuses on several key areas related to MMR technology: first, we conduct fundamental research to deepen the understanding of MMR technology itself. Secondly, we are developing spectroscopic methods for high-precision characterization and analysis of the sensors. Thirdly, we work on the development of inductively coupled sensing devices for the readout and manipulation of MMRs, alongside control methods for these resonators. Lastly, we are advancing the development of tracking and sensing methods to enhance the functionality and applicability of MMR technology in various medical and technological contexts.

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[192095]

Title: Natural Frequency Dependence of Magneto-Mechanical Resonators on Magnet Distance.

Written by: J. Faltinath, F. Mohn, F. Foerger, M. Möddel, and T. Knopp

in: <em>IEEE Sensors Journal</em>. (2025).

Volume: <strong>25</strong>. Number: (20),

on pages: 38073-38081

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DOI: https://doi.org/10.1109/JSEN.2025.3600007

URL: https://ieeexplore.ieee.org/document/11139087

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Note: article, openaccess, mmr

Abstract: The precise derivation of physical quantities like temperature or pressure at arbitrary locations is useful in numerous contexts, e.g., medical procedures or industrial process engineering. The novel sensor technology of magneto-mechanical resonators (MMRs), based on the interaction of a rotor and stator permanent magnet, allows for the combined tracking of the sensor position and orientation while simultaneously sensing an external measurand. Hence, the quantity is coupled to the torsional oscillation frequency, e.g., by varying the magnet distance. In this article, we analyze the (deflection angle-independent) natural frequency dependence of MMR sensors on the rotor-stator distance and evaluate the performance of theoretical models. The three presented sensors incorporate magnets of spherical and/or cylindrical geometry and can be operated at adjustable frequencies within the range of 61.9–307.3 Hz. Our proposed method to obtain the natural frequency demonstrates notable robustness to variations in the initial deflection amplitudes and quality factors, resulting in statistical errors on the mean smaller than 0.05%. We find that the distance–frequency relationship is well-described by an adapted dipole model accounting for material and manufacturing uncertainties. Their combined effect can be compensated by an adjustment of a single parameter, which drives the median model deviation generally below 0.2%. Our depicted methods and results are important for the design and calibration process of new sensor types utilizing the MMR technique.

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Institute for Biomedical Imaging

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Magneto-Mechanical Resonators

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