Carbon Fiber Felt-Reinforced Conductive Hydrogel Composite Sponge for Self-Powered Energy Harvesting and Strain Sensing

Conductive hydrogels are widely used in triboelectric nanogenerators (TENGs) and flexible strain sensors due to their excellent tunability and high electrical conductivity. In this study, a conductive-enhanced hydrogel composite sponge (PPFL-CFF) was prepared based on a composite system consisting of polydopamine (PDA), lithium chloride (LiCl), poly(acrylic acid) (PAA), ferric ions (Fe3+), and carbon fiber felt (CFF). With CFF as the polymerization framework of the hydrogel, the in situ polymerization of PDA was induced by adjusting the solution pH, and a multicross-linked network was constructed via metal coordination between Fe3+ and the carboxyl groups of PAA, as well as the catechol groups of PDA. Benefiting from the multiple synergistic effects of the materials, the PPFL-CFF hydrogel composite sponge exhibits outstanding comprehensive mechanical properties (0.47 MPa), electrical conductivity (37.23 S/m), antifreezing (nonfreezing at −10 °C), and moisture-retaining performance, as well as recyclability. Experimental results indicate that the hydrogel composite sponge exhibits an enhancement effect in compressive strength. Meanwhile, typical hysteresis loops are observed in the deformation range of 10–50%, indicating excellent energy dissipation and fatigue resistance properties. The self-powered TENG constructed on the basis of this hydrogel composite sponge can deliver an open-circuit voltage up to 120 V under the contact-separation mode, which is capable of powering small commercial electronic devices and rapidly charging various capacitors, while realizing self-powered strain sensing during signal transmission. Moreover, the flexible strain sensor fabricated from the material is suitable for human motion monitoring, with its generated waveform exhibiting a high degree of linear correlation with the motion state. This study provides a reference for the development of hydrogel-based flexible electronic devices and self-powered systems.