Electronic Measurements in an Alternating Magnetic Field for Studying Magnetic Nanoparticle Hyperthermia: Minimizing Eddy Current Heating

Abstract

In magnetic nanoparticle hyperthermia therapy and research, accurate sensors are required to monitor the temperature and, potentially, other parameters such as magnetic field or mechanical stress. Conducting materials undergo eddy current heating in an alternating magnetic field (AMF), which is problematic. However, eddy current heating is strongly dependent on the size and geometry of the conducting part, thus micro- or nano-scale electronics are a promising option. This paper reports calculations and measurements of self-heating in thin wires (thermocouples) and patterned thin films (resistive thermometers) in an AMF. Thin (40 gauge) type $E$ thermocouples show no significant self-heating compared with the background, while type $K$ and $T$ thermocouples and thicker (20 gauge) type $E$ , $K$ , and $T$ thermocouples show significant self-heating. A thin film resistive thermometer shows no significant self-heating compared with the background when placed parallel to the field, but has significant self-heating when placed perpendicular. Thus, electronic measurements in an AMF are feasible with appropriate material properties and geometries, and are a promising possibility for future investigations in magnetic nanoparticle hyperthermia.