The effect of washing on the electrical performance of knitted textile strain sensors for quantifying joint motion

Successful market penetration of textile-based strain sensors requires long-term reliability which in turn relies on the washability of the sensor. First, this paper presents an evaluation of the effect of 5 washing cycles on the electrical performance of a knitted conductive transducer, over 1500 cycles of repetitive elongation. The promising behaviour of the textile sensor in this study showed that it might be possible to make a smart garment, capable of quantifying elbow flexion-extension motion, by integrating it into an elbow sleeve. Second, a prototype sleeve, incorporating a knitted sensor (the so-called smart sleeve), was tested in a simulated training/clinical setting by performing 50 flexion-extension cycles after 1, 5, 15, 25, 50 and 75 washes. In both studies, the electrical resistance of the sensor increased with the number of washes in a predictable manner and exhibited a repeatable, reliable and prompt response to elongation. In particular, the electrical pattern representing flexion-extension motion measured using the sleeve was clear and distinguishable up to the 75(th) wash. Moreover, resistance measurements within the same trial were repeatable at maximum flexion (<= 2% variation) and at maximum extension (<= 3% variation) and predictable with increasing washes (R-2 = 0.992 at maximum flexion and R-2 = 0.989 at maximum extension). The good washability of the smart sleeve, evidenced by its ability to detect, distinguish and measure parameters of flexion-extension motion up to 75 washes, makes it a suitable and sustainable choice for applications, such as strength conditioning or rehabilitation, where repetition count and speed are useful.

Automated summary

This study evaluated the electrical performance of a knitted conductive transducer after multiple washing cycles and found it to have predictable, repeatable, and prompt response characteristics, suitable for creating smart garments. The smart sleeve prototype was able to accurately detect, distinguish, and measure flexion-extension motion parameters even after 75 washes, making it a sustainable choice for applications such as strength conditioning or rehabilitation.