Fully printed MWCNT strain sensor over paper substrate for human motion monitoring

Abstract

Flexible strain sensors have been used in myriad of applications with studies in human physiological monitoring, robotic operation, and human–machine interaction being intensively explored in recent years. Achieving a cost effective, high-performance flexible strain sensor with high sensitivity, and capable of large-scale production have great importance particularly for next generation of wearable electronics. In the present work, the authors have proposed a strain sensor which has been fabricated by simple screen printing of multi walled carbon nanotube ink over paper substrate in a facile and cost-effective manner. A thin sheet of polyethylene terephthalate. was laminated over the sensor surface to ascertain its stability towards environmental effects and physical movements. The characteristics of the printed strain sensor were systematically analyzed for its electrical performance with strain variations, repeatability, dynamic response and durability of the same was also investigated. The strain sensor exhibited a maximum gauge factor of 31.9 within the applied strain of 0%–1.72% and durability of 1000 bending cycles with a response and a recovery time of ∼13 ms and ∼17 ms respectively. Further, the fabricated strain sensors was also attached to various locations around human joints (knee, finger, elbow and wrist) and demonstrated significant sensing performance under different bending strains with superior mechanical robustness suitable for stable human motion monitoring for healthcare application.