Carbon nanotube reinforced ionic liquid dual network conductive hydrogels: Leveraging the potential of biomacromolecule sodium alginate for flexible strain sensors

The rapid evolution of multifunctional wearable smart devices has significantly expanded their applications in human-computer interaction and motion health monitoring. Central to these devices are flexible sensors, which require high stretchability, durability, self-adhesion, and sensitivity. Biomacromolecules have attracted attention in sensor design for their biocompatibility, biodegradability, and unique mechanical properties. This study employs a "one-pot" method to integrate ionic liquids and multi-walled carbon nanotubes into a dual-network hydrogel framework, utilizing tannic acid, sodium alginate, acrylamide, and 2-acrylamido-2-methylpropane sulfonic acid. Tannic acid and sodium alginate, natural biomacromolecules, form a robust physical crosslinking network, while P(AM-AMPS) creates a chemical cross-linking network. Ionic liquids enhance carbon nanotube dispersion, resulting in a hybrid hydrogel with remarkable tensile strength (0.12 MPa), adhesive properties (0.039 MPa), and sensing performance (GF 0.12 for 40 %-100 % strain, GF 0.24 for 100 %-250 % strain). This hydrogel effectively monitors large joint movements (fingers, wrists, knees) and subtle biological activities like swallowing and vocalization. Integrating natural biomacromolecules into this composite hydrogel sensor not only enhances the functionality and biocompatibility of flexible wearable devices but also paves the way for innovations in biomedicine and bioelectronics.