MWCNT-coated textiles for heating and temperature sensing under varying environmental conditions

In this study, a conductive cellulosic fabric was developed using a simple knife-edge coating method with multiwall carbon nanotubes (MWCNT) as conductive fillers and two different binders. The coated fabric was evaluated for its potential as an electrical heating textile and a temperature sensor. The investigation focused on the impact of environmental factors, including relative humidity and ambient temperature on the electrical heating performance of the coated textile samples. Increasing bio-based ink layers improved conductivity from 292 ± 38 S m^-1 for three-layer coating to 623 ± 120 S m^-1 for four-layer coating. IR thermal imaging revealed rapid Joule heating, with surface temperatures reaching 53 °C at 10 V. Relative humidity (RH) significantly influenced heating behavior, with peak surface temperatures observed at 70% RH, which was roughly 13 °C higher than that at 10% RH. While higher RH improved maximum surface temperatures, it also reduced initial heating rates. Conversely, lower ambient temperatures led to greater heat dissipation, reducing overall surface temperatures. We evaluated the electrical heating properties of the coated fabrics both without insulation and with different insulating layers, including cotton, viscose, and wool fabrics. This study identified optimal insulating layers for wearable heating pads. Wool provided superior heat retention, while the smooth and pliable cotton fabric proved ideal for skin contact, ensuring efficient heat transfer and breathability. The coated fabric also functioned as an accurate temperature sensor, exhibiting a strong linear relationship between temperature and measured resistance under ambient conditions. The Temperature Coefficient of Resistance (TCR) values confirmed its reliability and repeatability during cyclic heating and cooling.