Advances and challenges in conductive hydrogels: From properties to applications

The progress of soft robot industry has driven the development of electronic devices. Electronic devices used in electronic skin or wearable electronic devices require conductive materials with high sensitivity and stretchability, while traditional inorganic conductive materials such as metals and metal oxides cannot meet both conductivity and flexibility. Conductive hydrogels realize the complementary characteristics of conductive materials and hydrogels. On the basis of conductive materials ensuring electrical conductivity, hydrogels make up for the defect of unbendable material to a large extent and become the substitute of traditional inorganic conductive material. In order to adapt to different working environments, conductive hydrogels also have more excellent properties, such as mechanical properties, self-healing properties, and resistance to extreme environments, which further broadens the application field of conductive hydrogels. So far, conductive hydrogels have found wide applications in biomedicine, sensors and energy storage devices. In this paper, the research progress of conductive hydrogels in recent years is reviewed, and the conductive mechanisms of hydrogels can be divided into electronic conductive mechanism and ionic conductive mechanism. Then, the properties and applications of conductive hydrogels are described. Finally, the problems and shortcomings of conductive hydrogels were summarized, and the future development of conductive hydrogels was prospected.