Highly Stretchable, Tough, and Conductive Ag@Cu Nanocomposite Hydrogels for Flexible Wearable Sensors and Bionic Electronic Skins

Flexible conductive materials and flexible electronic devices are driving the development of the next generation of cutting-edge wearable electronics. However, the existing hydrogel-based flexible conductive materials have limited tensile capacity, low toughness, and poor anti-fatigue performance, resulting in narrow sensing area and insufficient durability. In this paper, a conductive nanocomposite hydrogel with high ductility, toughness, and fatigue resistance is prepared by combining silver coated copper (Ag@Cu) nanoparticles with gelatin followed by one-step immersion in sodium sulfate (Na2SO4) solution. The salting-out of gelatin in Na2SO4 solution greatly improve the mechanical properties of this gelatin-based hydrogel. The uniform distribution of Ag@Cu nanoparticles inside the whole hydrogel endow the composite hydrogel with excellent electrical conductivity (1.35 S m(-1)). In addition, it displayed high and stable tensile strain sensitivity over a wide strain range (gauge factor = 2.08). Therefore, the Ag@Cu-Gel hydrogel is sensitive and stable enough to be successfully utilized as flexible wearable sensor for detecting human motion signals in real time, such as bending of human joints, swallowing, and throat vocalization. Furthermore, this hydrogel is also suitable for application as electronic skin for bionic robots. The above results demonstrate the promising application of Ag@Cu-Gel hydrogel for wearable electronics.