Transparent, Mechanically Robust, Adhesive, Temperature-Tolerant, and 3D Printable Nanocomposite Ionogels for Flexible Sensors

Ionogels are emerging as soft materials for flexible strain sensors. However, the integration of multiple functionalities into a single ionogel for diverse applications in complex scenarios remains a challenge. In this study, we present a multifunctional nanocomposite ionogel that combines high strength, transparency, stretchability, temperature tolerance, adhesiveness, and 3D printing capabilities. The ionogels are fabricated through a one-step photopolymerization process involving acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in an ionic liquid, with Al(OH)₃ nanoparticles serving as cross-linkers. The resulting ionogels exhibit robust noncovalent interactions, including ionic coordination, hydrogen bonding, and ionic dipole interactions, providing exceptional mechanical strength, conductivity, and wide temperature tolerance while ensuring strong adhesion to various substrates. Wearable strain sensors based on these ionogels can accurately detect and differentiate a range of movements, from large body motions such as bending limbs to subtle distinctions such as writing different letters. Additionally, the pregel solution can serve as printing ink for the rapid and efficient mass production of 3D printed high-precision microcircuits. Impressively, the nanocomposite ionogels exhibit a high latent heat value of 240 J g^-1 at a melting temperature of -65 °C, suggesting significant potential for cold energy storage in ultralow-temperature cold-chain transportation systems. Thus, these outstanding features of the ionogels offer a promising strategy for advancing wearable electronics and cold energy storage systems.