Effect of temperature and frequency on Polyvinylidene Fluoride (PVDF) dielectric properties and its application for wearable Electromagnetic temperature sensor
In the human body, sustaining the core body temperature (CBT) is of great importance to maintaining proper cellular and body functions. The temperature of 37⁰C (98⁰F) is the well-established baseline and small variations are normal and expected depending on the environment and individual. However, when deviating significantly to under 35⁰C (95⁰F) or over 40⁰C (104⁰F), several health complications can arise such as fatigue, decreased mental and physical performance, fluctuations in blood pressure and cardiac irregularities which can progress to loss of consciousness or coma if untreated. In spaceflight missions, baseline body temperature has been recently been studied and shown to increase by 1⁰C gradually. If unnoticed, astronauts CBT could reach dangerously high levels when doing physically challenging tasks such as a spacewalk or exercise. Therefore, a real-time multi-physiological parameter sensing system is needed to be developed to noninvasively monitor the status of crew members in space. The objective of this thesis is to develop a novel temperature sensor using a wearable electromagnetic radio frequency (RF) self-resonating sensor. A temperature dependent dielectric material, polyvinylidene fluoride (PVDF), was characterized using a dielectric probe and displayed temperature and frequency dependent dielectric properties in the frequency range of the sensor system (10 MHz to 3 GHz). Thin sheets of PVDF were integrated into the sensor system design as a substrate that interacts with the electromagnetic field created by the spiral sensor to result in a quantitative temperature monitoring sensor with an accuracy of 1⁰C. The study also displays that the studies using polyimide-based electromagnetic RF sensor systems are not impacted by small temperature changes. Future incorporation of this wearable temperature sensor will provide a thin, flexible, noninvasive method to monitor body temperature alongside vital signs of crew members in space.
Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Biomedical Engineering