Facile fabrication of a stretchable, stable, and self-adhesive poly(ionic liquid) as a flexible sensor

Although poly(ionic liquid)s (PILs) are alternative materials to flexible hydrogel sensors owing to their unique characteristics such as nonvolatility, high conductivity, and excellent temperature tolerance, their weak mechanical properties greatly limit their application in flexible sensors. In this study, a PIL with high stretchability, excellent stability, and remarkable self-adhesive property was fabricated by the in situ photopolymerization of 1-vinyl-3-butylimidazolium bis(trifluoromethylsulfonylimide) ([VBIM]TFSI) and butyl acrylate (BA) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonylimide) ([BMIM]TFSI). The outstanding electromechanical properties, including instant response, improved stretchability, low hysteresis, and prominent repeatability, of the resulting PIL imparted it with strain-sensing capacity for recognizing a variety of physical deformations, such as human joint activity and pulse. Moreover, since the change in the conductivity of PILs with temperature conforms to the Vogel–Tamman–Fulcher (VTF) equation, the PIL could be utilized as a high-performance temperature sensor. Thus, this work provides a facile strategy for fabricating a high-performance bimodal PIL sensor, which has broad prospects for flexible electronics.