Temperature-driven soaking of hydrogels for high-performance triboelectric nanogenerators in wearable electronics

Emerging conductive hydrogel-based flexible and stretchable triboelectric nanogenerators (TENGs) have garnered significant attention due to their remarkable performance. Despite extensive research on hydrogels, the potential of temperature-dependent ionic solution soaking to enhance their properties remains relatively underexplored. In this study, a highly sensitive conductive hydrogel is fabricated by physical crosslinking of polyvinyl alcohol (PVA) with sodium nitrate (NaNO₃) through a freeze-thaw process, coupled with a temperature-driven NaNO₃ solution soaking. The effect of varying temperatures, including room temperature (RT), 60 ℃, 80 ℃, and 100 ℃, on salt-soaking structural, electrical, and mechanical properties of hydrogel over time was comprehensively investigated. Remarkably, the hydrogels achieved a conductivity of 23.93 S/m when immersed in NaNO₃ solution as compared to the unsoaked hydrogel (2.35 S/m). The PVA/NaNO₃ hydrogel-based TENG devices delivered an impressive performance, generating an output voltage of 59.6 V and a current of 6.36 µA. Additionally, hydrogel exhibited superior mechanical properties, with a tensile strength of 0.65 MPa, attributed to temperature-induced salting-out effects. These findings highlight the significant promise of conductive hydrogels in advancing flexible energy-harvesting and sensing systems, opening new pathways for the development of efficient and versatile wearable technologies.