Biosensors and Bioelectronics: X (Dec 2022)
Investigation of textile permittivity under the influence of fever for designing a wearable temperature sensing antenna
Abstract
This paper aims to monitor human fever using wearable sensors as a non-invasive and real-time method. Our purpose is based on the use of textile sensors that can be integrated with the person’s clothes. The origin of antenna sensor measurement presented here is based on changes in fabric relative permittivity related to variations in body temperature in the range from 35 °C to 41 °C. The structure is such that a microstrip patch antenna is implemented on the textile in the X frequency band. In the first step of designing the sensor, the measurement setup is designed to extract εr and tan δ characteristics of various commercial fabrics using a Keysight N1501A-101 high temperature dielectric probe. After examining a few samples of different fabrics in the setup, the commercial cashmere fabric with the highest changes in relative permittivity is selected to design the antenna sensor. The rate of change in relative permittivity of this fabric is about 0.02 for a temperature step of 2 °C. The antenna sensor provides a frequency shift of 60–80 MHz per temperature step in the X frequency band. The frequency shift per 1 °C is found to be about 35 MHz, which is acceptable and can provide good temperature detection. Given that fever is one of the main symptoms of many diseases and that its early detection can prevent endangering people’s lives, the proposed wearable sensor may find important applications in fever monitoring.
