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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Publications

[164758]
Title: Empirical Study of Magnet Distance on Magneto-Mechanical Resonance Frequency.
Written by: T. Knopp, F. Mohn, F. Foerger, F. Thieben, N. Hackelberg, J. Faltinath, A. Tsanda, M. Boberg, and M. Möddel
in: <em>Current Directions in Biomedical Engineering</em>. 12 (2024).
Volume: <strong>10</strong>. Number: (4),
on pages: 377-380
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DOI: http://dx.doi.org/10.1515/cdbme-2024-2092
URL: https://www.degruyterbrill.com/document/doi/10.1515/cdbme-2024-2092/html
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Note: inproceedings, mmr

Abstract: Determining the position and orientation of a medical instrument is essential for accurate procedures in endoscopy, surgery, and vascular interventions. Recently, a novel sensor based on torsional pendulum-like magneto-mechanical motion has been proposed. This sensor is passive, wireless and inductively coupled to a transmit-receive coil array. This setup allows the determination of all 6 degrees of freedom using the characteristic resonance of the sensor. Additional physical quantities such as temperature and pressure can be measured based on the frequency of the sensor, which mainly depends on the distance between the two involved permanent magnets. In this study, we analyze a sensor composed of two magnetic cylinders with variable magnet-to-magnet distance and a basic physical model based on a dipole assumption. Experimental analysis of the resonance frequency and comparison with the model values show both qualitative and quantitative agreement with an average relative error of only 0.8 %. This validates the implemented model and shows the suitability of our magnetic-mechanical resonator made from cylindrical permanent magnets for sensing applications.