Transparent, Stretchable, and Adherable Ionogel with High Electrical Conductivity for Flexible Strain Sensors

Ionogels have attracted considerable attention for application in flexible electronics. However, it is still challenging to prepare multifunctional ionogels with high transparency, stretchability, adhesion properties, and electrical conductivity by simple processes. Therefore, we report a one-step process for the preparation of a multifunctional ionogel, in which the polymer monomers acrylamide and hydroxyethyl methacrylate are dissolved in 1-ethyl-3-methylimidazolium chloride, and then the multifunctional ionogels were prepared by a photoinitiated copolymerization. Based on the good compatibility between ionic liquid and polymer monomer, as well as the hydrogen bonding and ion–ion interaction in the gel network, the obtained ionogels exhibited high transparency (>95%), elongation at break (>410%), adhesion properties (744 kPa, with glass as the substrate), and electrical conductivity (3.39 × 10–4 S/cm). In addition, the strain sensor prepared with ionogels can be used to monitor human joint motion. This work provides a simple way to prepare multifunctional ionogels for flexible strain sensors.