Induction heating-based low-frequency alternating magnetic field: High potential of ferromagnetic composites for medical applications

Abstract

This study focusses on a low-frequency induction heating (LFIH) effect in a thermoplastic polymer (acrylonitrile butadiene styrene, ABS) filled with iron oxide magnetic particles. The LFIH effect in such ferromagnetic composites appears as soon as the sample is exposed to an alternating magnetic excitation field and is mainly due to the so-called “microscopic” eddy currents linked to the motions of the magnetic domain wall. To generate an AC magnetic field with significant amplitude under a low-frequency range of a few thousand Hz, a specific test bench has been designed using a rotating motor and strong permanent magnets. Theoretical hysteresis modeling, together with thermal transfer based Comsol simulation and experimental tests, demonstrated the feasibility of significantly increasing the temperature of a magnetic composite through a simple induction heating effect. To better highlight such an effect, a comparison with conductive but non-ferromagnetic samples was performed. As opposed to the ferromagnetic composite, its conductive counterpart exhibited a very weak response to the magnetic field excitation, and no temperature effect was achieved. This observation can be explained by “microscopic” eddy currents (i.e., the fact that domain wall motions are predominant mechanisms under low frequency), leading to local temperature variations inside the ferromagnetic particles. These preliminary results seem to be promising, and this effect could be exploited in a medical application, especially for treatment of superficial venous insufficiency, where local heating remains a true challenge. As normal tissues and muscles are conductive, it is necessary to bring the heat “where it is needed”. We believe that LFIH would be able to destroy varicose veins without damaging the neighboring tissues. Keywords: Ferromagnetic composites, Hysteresis loss, Microscopic eddy current, Low-frequency induction heating, Thermal transfer modeling, Treatment of superficial venous insufficiency, Medical applications