Stretchable and Tough Conductive Hydrogels for Flexible Pressure and Strain Sensors
Flexible pressure and strain sensors have great potentials for applications to wearable and implantable devices, soft robotics and artificial skin. Compared to flexible sensors based on filler/elastomer composites, conductive hydrogels are advantageous for their biomimetic structures and properties, as well as biocompatibility. Numerous chemical and structural designs provide unlimited opportunties to tune the properties and perofrmance of conductive hydrogels to match various demands for practical applications. Many electronically and ionically conductive hydrogels have been developed to fabricate pressure and strain sensors with differnet configurations, including resistance type and capacitance type. The sensitivity, reliability and stability of hydrogel sensors are dependent on the network structures and mechanical properties. This review focuses on tough conductive hydrogels for flexible sensors. Representative strategies to prepare stretchable, strong, tough and self-healing hydrogels are briefly reviewed since these strategies are illuminating to the development of tough conductive hydrogels. Then, a general account on various conductive hydrogels are presented and discussed. Recent progresses on tough conductive hydrogels with well designed network structures and their sensory performance are discussed in detail. A series of conductive hydrogel sensors and their application for wearable devices are reviewed. Some perspectives on flexible conductive hydrogel sensors and applications are presented at the end.