"All-in-one" ink for light-based 4D printing of conducting, tough, anti-freezing, and cytocompatible hydrogels

High-performance hydrogel-based electronic devices require conducting hydrogels. Conducting hydrogels that are stretchable, soft, and biocompatible are in much demand to fabricate human -machine interfaces, wearable devices, soft robotics, and many other applications. We present a new generation polymeric formulation to prepare hydrogels by digital light processing (DLP)-based three-dimensional (3D) printing technology with visible light that are anti-freezing, electrically conductive, tough, stretchable, and non-toxic. The printed conducting hydrogels have exceptional water-holding capability at atmospheric conditions and tolerance to freezing over a wide range of temperatures from- 80 to 45 degrees C. The inks are amenable to the manufacturing of fourdimensional (4D)-printed hydrogels that can elicit pre-programmed structural deformations. This work presents polymeric formulations for potentially designing ultrafast programmable electronic devices with printed hydrogel electronics in various biomedical applications, soft robotics, biosensors, flexible electronics, human-machine interfaces, and health monitors for use under extreme environmental conditions.