Transparent, stretchable, self-healing, and self-adhesive ionogels for flexible multifunctional sensors and encryption systems

Abstract

Conductive gels are promising soft ionic conductors for stretchable and flexible electronics. However, the integration of multiple functions into one gel remains a great challenge, as the tailoring of these properties is mutually exclusive. In this paper, a simple photopolymerization method is designed to prepare polyacrylic acid/ionic liquid /hydroxypropyl cellulose (PIH) ionogels, which have high transparency (89 %), and superior electrical conductivity (0.379 mS/cm). Owing to the dynamic and reversible nature between the polymer chains, the ionogel possesses good self-healing capability (79.6 %) and self-adhesive properties (242.32–742.76 kPa, typical substrate at room temperature). At the same time, the excellent chemical stability of ionic liquids ensures that PIH ionogels still have good temperature sensitivity (-30 ∼ 110 °C) in extremely harsh environments. Wearable strain sensors based on PIH ionogels can sensitively detect and distinguish body movements, such as limb bending, pronunciation, and pulse. When PIH ionogels are used as a temperature sensor, a cryptographic device with a temperature alarm and an externally stimulated UV switch is designed by using the excellent transparency and temperature response of PIH ionogels. It is believed that the designed ionogel will show great prospects in wearable devices and flexible encryption.