Flexible Wearable Sensors Based in Carbon Nanotubes Reinforced Poly(Ethylene Glycol) Diglycidyl Ether (PEGDGE): Analysis of Strain Sensitivity and Proof of Concept

The electromechanical capabilities of carbon nanotube (CNT) doped poly(ethylene glycol) diglycidyl ether (PEGDGE) have been explored. In this regard, the effect of both CNT content and curing conditions were analyzed. The electrical conductivity increased both with CNT content and curing temperature due to the lower gel time that leads to a lower reaggregation during curing. More specifically, the percolation threshold at 160 and 180 °C curing temperatures is below 0.01 wt.%, and this limit increases up to 0.1 wt.% at 140 °C for an 8 h curing cycle. Moreover, the strain monitoring capabilities were investigated, and the effect of contact resistance was also analyzed. The electrical contacts made with silver ink led to higher values of gauge factor (GF) but presented some issues at very high strains due to their possible detachment during testing. In every case, GF values were far above conventional metallic gauges with a very significant exponential behavior, especially at low CNT content due to a prevalence of tunneling mechanisms. Finally, a proof of concept of fingers and knee motion monitoring was carried out, showing a high sensitivity for human motion sensing.