One-pot synthesis of strongly adhesive 3D printable gelatin/carrageenan conductive hydrogels for flexible sensors and supercapacitors

Polymer hydrogels have been widely studied for their conductivity, adhesiveness, and 3D printing properties, but preparing hydrogels with both adhesion and printing capabilities remains a challenge. This study reports the one-pot synthesis of a Gelatin/Agar/κ-carrageenan (Gel/Agar/κ-CA) ternary network hydrogel with simultaneous printability, adhesiveness. By leveraging metal-ligand bonds, it overcomes the compatibility challenge of multi-functional components, offering a new paradigm for 3D-printed flexible devices. Enabled by metal-ligand interactions, the hydrogel adheres to diverse substrates, withstands 20 kg ferrous materials at 1.4–25 °C, and supports both planar and 3D printing. A hydrogel-based supercapacitor exhibits stable cycling performance after 38,000 charge/discharge cycles. This work not only develops a strongly adhesive hydrogel but also provides new pathways for 3D-printed flexible sensors and energy storage devices. As a thermoreversible gel, agar maintains fluidity at 60 °C during printing and rapidly gels upon cooling, ensuring high-fidelity fabrication. Amino groups in gelatin form hydrogen bonds with hydroxyl and sulfate groups of κ-carrageenan, enabling multi-substrate adhesion. Sulfate groups in κ-carrageenan immobilize cations to form conductive pathways, while protonated amino groups in gelatin form ion pairs with chloride ions to enhance ion mobility, collectively supporting sensing and energy storage applications.