Integration of temperature sensors in fabrics

This paper reports the integration of temperature sensing filaments within a fabric structure using an industrial textile weaving process. The filament is inserted into bespoke pockets woven within the body of the fabric which conceals the electronic functionality from the user and does not compromise the physical properties of the fabric. The thermistor on the filament is protected with a flexible encapsulation consisting of one or a combination of a hot melt thermoplastic polyurethane (TPU), two polyimide films (PI) and blends of polyester/cotton fabrics of varied thicknesses. In e-textiles, encapsulations enhance the durability and life-time of the integrated electronics but can also limit the sensitivity of an enclosed sensor to its measurand. The effect of these encapsulations on the thermal sensitivity of the thermistor was investigated. Experimental results show that temperature measurements of the encapsulated sensors enclosed with the fabrics are accurate to 80 % confidence interval of the un-encapsulated sensor measurement between 30 °C and 65 °C. Temperature measurements are useful in the monitoring of foot ulcer and wound infections of diabetic patients [1] , changes in skin or ambient temperatures [2] and cardiovascular health evaluations [3] for health applications. In designing e-textile garments for such applications where users desire the sensors to be completely enclosed within the fabric, the results shows that reducing the fabric and encapsulation thicknesses around the temperature sensor can improve the cooling time of the sensor by 40%.