3D Printed Ultrasensitive Graphene Hydrogel Self-Adhesive Wearable Devices

Ionic hydrogels are conductive and stretchable, showing great potential for applications in flexible wearable devices. However, poor mechanical and electrical properties, low manufacturing precision, and lack of self-adhesion severely limit their practical applications in hydrogel wearable devices. Herein, we propose a stretchable, highly conductive, and self-adhesive ionic hydrogel fabricated with an LCD light-curing 3D printing technique. 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), 4-hydroxybutyl acrylate (HBA), and graphene are incorporated to prepare the printable ion-conductive hydrogel. The results show that this hydrogel exhibits outstanding electrical conductivity (0.0487 S/cm), excellent linear sensitivity (GF = 1.86 within 100% strain), amazing stretchability (1200% strain), and strong adhesion performance with various materials. Furthermore, the HBA–AMPS–graphene (HAG) hydrogel-based flexible wearable devices can monitor various human movements from tiny scale (breathing and speaking) to large scale (such as elbow and knee joint movement). Most significantly, the hydrogel wearable devices can capture the signals of pulse beating and breathing, which are so light that they are hard to be monitored. Our printable ionized hydrogel wearable devices promise applications in motion monitoring, health detection, human–machine interface, and so on.