A biocompatible inexpensive strain sensor constituting of an elastomer filled with natural coconut oil (CNO) and carbon black (CB) is presented here. Strain sensors are widely utilized for applications in human activity recognition, health monitoring, and soft robotics. Given that these sensors are envisioned to be present in a plethora of fields, it is important that they are low cost, reliable, biocompatible, and eco-friendly. This work demonstrates that CNO can be used to create conductive percolation network in elastomers, without the necessity for harmful chemicals or expensive machinery. The sensor has a gauge factor of 0.77 ± 0.01, and the sensing material has a porous morphology filled with an oily suspension formed of CNO and CB. Results indicate that the liquid filled porous structure can improve the reliability of these resistive strain sensors in comparison to sensors fabricated utilizing commonly used non-polar solvents such as heptane. Consequently, the sensor demonstrates a hysteresis of only 2.41% at 200% strain over 250 stretch/release cycles. Finally, to demonstrate the potential of this fabrication technique, a functionalized glove is developed and used to detect wrist motion. These easily manufacturable and cost-effective sensors enable wearable on-skin ergonomic intervention systems with minimal impact on the environment.
Bibliographical noteFunding Information:
P.L., N.M., and J.C.C. conceived and designed the experiments; P.L. synthesized the material; P.L. and L.A.G.‐G prepared the samples and the sensors; P.L. and J.C.C. performed the experiments; P.L. and J.C.C. analyzed the data; J.S. did the SEM imaging of the materials; Z.S. and P.L. conducted the wrist motion experiment and analyzed the data; N.M. provided expertise in flexible electronics; D.R. provided expertise in data analysis; P.L., J.C.C., L.A.G.‐G., and A.P. wrote the paper with input from all authors; D.R. and N.M. supervised the work. The authors will like to thank Dr. Martina Costa Angeli for assisting with the experiments. The authors also thank Kalana Marasinghe for his assistance with the figures. All authors have read and agreed to the published version of the manuscript. This work was partially funded by EPSRC, GCRF, and NIHR, under the contact number: EP/R013837/1 (SmartSensOtics).
© 2020 Wiley-VCH GmbH
- carbon black
- cocos nucifera oil
- eco-friendly sensors
- strain sensors
- wearable devices