A transparent and ionic liquid enhanced conductive hydrogel with a hybrid double network as a stretchable strain sensor

Abstract

Conductive hydrogels have attracted great attention for their broad application prospects in flexible electronics. However, it usually remains a trade-off between mechanical strength, low-temperature tolerance, and conductivity and will restrict their applications in wearable electronics. Here, the ionic liquid ([EMIM]Cl) is introduced into the double network (kcarrageenan/Poly(acrylic acid) (PAA)) to prepare the ionic conductive hydrogel by a simple one-pot polymerization method. The fabricated conductive hydrogel presents excellent mechanical properties, including high fracture stretchability (2655%), tensile strength (135 KPa), and low Young’s modulus (13.9 KPa). Benefiting from the high ionic conductivity and low freezing point of the ionic liquid, the conductive hydrogel can demonstrate a high conductivity up to 2.88 S/m at room temperature, as well as good freezing tolerance (-11°C). Owing to the good compatibility of the ionic liquid, the conductive hydrogel has good transmittance. Furthermore, the transparent ionic skin based on the as-fabricated conductive hydrogel is demonstrated toward the tensile deformation to detect the human motion signals. This work provides a way to design transparent conductive hydrogels with excellent mechanical strength, good anti-freezing, and high conductivity for potential applications in wearable sensing devices.