Investigating construction and design parameters of an embroidered resistive pressure sensor

Electronic textiles, or smart textiles, is a field that is growing due to the opportunities it provides. Textile integrated electronics enables soft, flexible, lightweight electronic devices that enable long term monitoring within the medical field. Pressure sensors is one device within this field that has been researched. A textile integrated pressure sensor enables monitoring of heart rate, muscle activity, posture, gait phases and finger movements. In this project a resistive pressure sensor has been produced using embroidery with the purpose of investigating how construction and design parameters influence the resistance-pressure relationship. The study consisted in different phases where in Phase I parameters such as fabric substrate, stitch length and yarn type was examined. Phase II investigated design parameters like electrode pattern design, sensor shape, trace distance and size. In the design phase a new electrode pattern and sensor shape was tested. Finally in Phase III a sensor matix and sensor chain was constructed in order to evaluate the possibility of obtaining touch location. The findings in this study showed that the shape, size and yarn type had the most distinct influence on the sensor performance in regards to the resistance-pressure relationship. In an additional recovery test the results indicated that both textile substrate and stitch length could influence the ability to recover to its original shape after applying cyclic pressure. It was also found that the new pattern design performed equally to the conventional pattern designs and at the same time reduced material consumption as well as the embroidery time. The sensor matrix and sensor chain could display a change in resistance when applying a weight at each sensing element, implying that touch location could be detected, but would need further development in construction before potential implementation.