Sustainable conductive ink for printing high performance wearable sensors

Abstract

Advances in wearable sensors especially for health monitoring are breaking strides to meet the insatiable appetite for data that is demanded by the internet of things. This has been spurred on by fabricating sensors with conventional printing techniques. An underlying challenge is to improve the ecological impact of printing inks without sacrificing either their conductivity or sensor performance. To this end, we present a fully water soluble, self-doped conductive polymer (pPDS) ink formulated using environmentally benign water. The ink was optimized for conventional printing methods, flexography and screen printing, on a broad range of flexible substrates including fabrics, PET, and paper. The printed ink retained its intrinsic conductivity on the substrates and it enabled high performance relative humidity (RH) and temperature sensing. The response and recovery times of the sensors were 15 s and 26 s, respectively, at 22% and 75% RH, whereas the temperature sensor was independent of humidity at 40% and 80% RH with a −2.2% °C⁻¹ sensitivity. Unlike sensors based on conventional PEDOT:PSS and complex device architectures, the single-printed strip sensor offers a simple and straightforward alternative design for the potential non-invasive monitoring of respiration directly from printed textiles. The integration of sustainable conductive inks with direct-to-textile printing advances the field of wearable, passive health diagnostics, paving the way for scalable, environmentally responsible electronic sensing technologies.