In recent years, many industries are showing great interest in sustainable and digitalised societies, with concepts such as cyber-physical systems (CPS). In doing so, efficiency data collection on a large scale and in real-time has become a crucial point of concern. From the initial data acquisition to the data storage and communication component of a CPS, maintaining a sensible efficiency and accuracy is of paramount importance for a sustainable society. One type of physical data that is crucial in various systems throughout society is temperature. Temperature is often one of the key indicators or parameters of any given physical system. Some of the conventional temperature-sensing methods include thermography and the use of thermistors or thermocouples. However, these methods have points of concerns, such as with the need for calibration, operation cost, and more. In this research, the authors propose a novel energy harvesting sensor with a possible application for a temperature data acquisition device. This can for instance be for monitoring body temperature, which is not only important for our society in terms of public health, but also a highly quantifiable measure for monitoring health. The proposed device utilises the magnetic properties of materials as the working principle in order to produce electricity from low-quality subject heat while simultaneously monitoring the temperature. When a magnetic material is subjected to an external magnetic field, the magnetic moments of the material align, thereby causing the material to magnetise. The degree of magnetisation, or magnetic susceptibility is characterised by Curie’s law as being dependent on the material temperature. As the material approaches its Curie Temperature, a magnetic phase change occurs, causing a corresponding magnetic flux change. By incorporating electromagnetic induction with solenoids, the magnetic flux change of a known probe material could be measured as a voltage. Thus, this phenomenon can be applied for an energy harvesting temperature sensor in the near range of a material’s Curie Temperature, as the voltage reading is representative of the magnetic flux change and thus the material temperature. With an appropriate material, the device has the potential to operate as a temperature sensor for various targets.
Past explorations by the authors have shown that the application of magnetic phase transition for a temperature sensor based on magnetisation change is especially promising in the phase transition temperature region around the Curie Temperature of the material. Therefore, it is necessary to identify and develop a probe candidate material that has the appropriate magnetic properties for the sensing subject. Here, an investigation on the probe material and its potential implications on the expected performance of the proposed sensor device. Specifically, a consideration of the magnetisation-temperature curve and electromagnetic induction magnitude is conducted on probe material candidates. Additionally, a theoretical approach to the formulation of a mathematical model for the sensing scheme has been conducted to quantitatively characterise the properties of the proposed device. The results of the study show the potential of the proposed device, with an appropriate probe material, as a temperature sensor for various sensing subjects.
