3D printable ionic conductive hydrogels with super stretch and self-adhesion performances for flexible sensors

Ionic conductive hydrogels (ICHs) have emerged as a landmark soft material for a wide range of applications, such as flexible wearable sensors and electronic skins. However, to achieve a superstretchability, high strength, and self-adhesion simultaneously by 3D printing remains a significant challenge. In the construction of a hydrogel, ionic liquids (ILs) and tannic acid (TA) have been successfully introduced in the copolymerization of acrylamide (AAm) and poly(ethylene glycol) (diol) diacrylate (PEGDA) to form a p(AAm-co-PEGDA) hydrogel (PAP) system. The PAP hydrogel showed superstretching (4300%), high strength, and self-adhesion properties. More specifically, the 3D printing of the ICHs provided an effective and flexible way to manufacture flexible wearable sensors, thus greatly simplifying the device fabrication process. In addition, the sensors could be specified by a customized production and were, thus, adapted to a wider range of applications. It is believed that the here presented hydrogel integration with 3D printing will inspire new ideas on how to prepare novel flexible sensors, thus promoting further research on the construction of electronic skins, human-computer interactions, and advanced materials.