Dielectric Characterization of Fabric-Sweat Mixtures Using Microstrip Transmission Lines for Antenna-Based Sensing Applications

In the realm of electronics and textile integration, fabric-based substrates for antennas, resonators, and sensors have emerged as innovative alternatives to traditional rigid printed circuit boards. Methods for measuring the dielectric properties, including relative permittivity and loss tangent, re-main limited, especially in relation to fabric-liquid mixtures. To address this gap, this study uses the Transmission Line Method to characterize the dielectric properties of fabric-sweat mixtures in both euhydrated (i.e., regular hydration) and dehydrated states for RFID hydration monitoring applications. This study presents a set of experiments to compute the dielectric properties of the mixtures with three different fabric materials (jeans, cotton, and polyester), two types of sweat (euhydrated and dehydrated) and different amounts of sweat injected into the fabric. The results confirm the feasibility of measuring the relative permittivity and the loss tangent of fabric-liquid mixtures at 800–1000 MHz.