Engineering PDA@CNTs-Enhanced sulfobetaine methacrylate hydrogels for superior flexible sensor applications

Conductive hydrogels have attracted significant attention as versatile materials for flexible sensors, with potential implementation in wearable technologies, electronic skins, and health diagnostics. However, traditional hydrogel models are frequently limited by their inadequate mechanical strength, poor conductivity, weak adhesion, and low durability, which pose significant barriers to their further application in flexible sensors. In this work, we prepared composite multifunctional hydrogels as flexible sensors, which were synthesized from sulfobetaine methacrylate SBMA) and acrylamide (AM), infused with dodecyl quaternary ammonium salt (Q12), and incorporated with poly(dopamine)-functionalized carbon nanotubes (PDA@CNTs). The PDA modification enhances the compatibility of CNTs with the hydrogel matrix. The incorporation of PDA@CNTs into the hydrogel matrix, along with the establishment of multiple dynamic bonds—such as ionic bonds, hydrogen bonds, cation-π interactions, and π-π stacking between polymer chains and PDA moieties—significantly enhances its tensile strength (53.79 kPa), toughness (134.77 kJ/m³), adhesive capabilities (29.84 kPa to paper), and electrical conductivity (0.2 S/m). Moreover, the composite hydrogel reveals a remarkable mechanical strain response, coupled with impressive stability and durability over prolonged periods. It efficiently differentiates between mild elongations (10%–40 %) and substantial elongations (50%–300 %), thereby showcasing its capability for real-time biomechanical motion monitoring. Additionally, the composite hydrogel displays remarkable photothermal antibacterial efficacy upon exposure to near-infrared (NIR) radiation, along with outstanding biocompatibility under standard conditions, thereby confirming its suitability for safe and long-term biological interactions. The exceptional functionality of these composite hydrogels renders them highly conducive to diverse applications in the realm of wearable sensor technologies.