Executive Summary : | Core body temperature (CBT) is one of the vital physiological parameters that indicate the health of humans. The CBT of healthy humans at resting state lies between 36.5 to 37.5C and any deviation from this range is an indicator of infection, illness or heat stress. Accurate measurement of CBT is possible only through pulmonary artery temperature measurement which is the gold standard. Due to the invasive nature, it is not widely adopted and is not possible in all scenarios. Alternate measurement sites that are minimally invasive for CBT which yield measurements close to the gold standard are oesophagus and rectum, which are also limited to hospital settings. Other non-invasive measurement sites reported for CBT are oral, ear auditory canal (EAC), axilla and forehead. Among these sites, measurements EAC was observed to yield better accuracy with the gold standard. Temperature measurements in EAC carried out using tympanic infrared thermometer are easy to use and yield relatively fast measurements. However, large variation in measurements were reported as thermal radiation from the tissue surface gathered by infrared thermometer is influenced by wax and hair in the EAC, and sensor placement in the EAC. Besides hospitals, sports training centre, fitness centre, athletes and fire fighters exposed to heat stress also require continuous monitoring of CBT for long duration. Wearable sensors reported for body temperature monitoring to cater for such scenarios are only capable of measuring superficial tissue temperature and not the CBT. Unlike peripheral non-invasive thermometry techniques reported for CBT, microwave passive radiometry is a non-invasive deep tissue thermometry technique (several cm deep) that is not influenced by the ambient temperature and pressure. CBT measurement using microwave radiometry has been reported using large near field contact type planar microwave antennas placed on the forehead or sternum which are bulky and susceptible to ambient electromagnetic interference. Furthermore, the sites chosen for CBT using microwave radiometer are known to have larger measurement error than the EAC and axilla. The novel research components in this work are (i) development of miniaturized wearable passive microwave radiometer for CBT monitoring, (ii) synthesis of low loss high k engineering ceramics for microwave antenna miniaturization, and (iii) 3D printing of engineering ceramics for antenna fabrication. The following salient features add to the novelty of the proposed wearable device: • Use of passive microwave radiometry • Non-invasive method for CBT measurement • Deep tissue thermometry by gathering thermal radiation from the carotid artery • Measurement stability to presence of wax or hair in EAC • Use of engineering ceramics for near-field microwave antenna • Wearable near-field antenna fabrication via 3D printed complex molds • Improved measurement stability as internal sensor is not influenced susceptible to ambient EMI |