Knitted Smart Textile Sensors

Abstract

Nowadays, people are using more and more technology to measure their body performances like smart watches, heart rate sensors etc. These are all separate devices. What if it were possible to integrate these into something we wear daily. Textiles are something everyone wears daily. It is a promising medium to integrate electronics in. Especially through knitting new possibilities arise. Different conductive and non-conductive yarns are explored with a focus on off-the-shelf available materials. The main yarn needing to be elastic to get the fabric back to its normal position after stretching. Knitted fabrics have a unique structure which is perfectly suited to create sensors with. A knitted fabric is stretchable without the yarn needing to be stretchable. This makes searching for good working conductive yarns easier, as non-stretchable conductive yarns are a lot more common. Previous research shows that creating sensors through knitting is possible and can be achieved with simple yarns. The structure of knitted fabrics is mainly useful for creating strain sensors. Using elastic yarn with silver conductive plated yarns, different sensor test samples are created. Optimization is done to improve the sensors' signal output. Two directions for knitting a sensor were tested. The optimized sensors are used in two prototypes that are able to measure the movement of the arm and the breathing pattern of the wearer. The arm movement prototype is tested with two sensors knitted in the vertical (wale) direction and the breathing sensor was made with a long strip of a sensor knitted in the horizontal (course) direction. Both arm and breathing sensors are integrated into a full garment prototype. This prototype is tested by doing different movements and seeing how movements affect the sensor behaviour. Possible designs of a shirt with integrated arm and breathing sensors are briefly discussed to show how the look of the shirt and the integrated sensors could complement each other. The final prototype's sensor data is evaluated and recommendations are made for follow up projects based on this research. This research sets a new and fruitful step in the direction of producing commercially viable body measurement clothing for the near future.