Ultra-stretchable, self-adhesive, antifreezing polyacrylamide/sodium alginate/polydopamine@carbon nanotubes conductive hydrogel for human micro-expression, electrocardiographic and motion signal monitoring

Flexible sensors are indispensable components in wearable electronic devices and have great potential for applications in human health monitoring, human–machine interfaces and robotics. Conductive hydrogels have emerged as key materials for flexible sensor fabrication due to their exceptional modulus, elasticity and conductivity. Polyacrylamide (PAM) and sodium alginate (SA) were employed as the base materials, while glycerin and water were used as a binary solvent, and polydopamine-modified carbon nanotubes (PDA-CNTs) acted as conductive fillers to enhance conductivity and improve the mechanical properties of the hydrogel. A sensitive, self-adhesive and super-stretchable conductive hydrogel was successfully synthesized, which was designated as glycerol–water–polyacrylamide/sodium alginate/polydopamine-modified carbon nanotubes (GW-PAM/SA/PDA@CNTs). Experimental findings demonstrate that this hydrogel exhibits excellent mechanical properties, tissue adhesion, antifreezing and heat-resistant properties, self-healing and long-term stability. Moreover, it facilitates the monitoring of human motion signals, facial micro-expressions and electrocardiographic (ECG) signals. This study proposes a novel design strategy for the development of a multifunctional conductive hydrogel.