Multiscale Design Principles for Nanocomposite Hydrogel-Based Triboelectric Nanogenerators

Hydrogel-based triboelectric nanogenerators (H-TENGs) are soft, self-powered platforms for wearable sensing, human-machine interfaces, and biomechanical energy harvesting. Hydrogels offer mechanical compliance, ionic conductivity, and skin conformability, but practical H-TENGs remain limited by insufficient mechanical robustness, limited electrical or ionic transport, and limited output performance. Nanofiller engineering provides a materials-level route to address these limitations by reinforcing hydrogel networks, improving transport pathways, and tailoring interfacial charge behavior. This Mini-Review summarizes recent progress in nanocomposite H-TENGs with emphasis on mechanical reinforcement, electrical pathway engineering, nanofiller dispersion control, output modulation, and multifunctional integration. Rather than treating nanofillers as simple additives, we highlight how their dispersion, surface chemistry, and spatial arrangement govern hydrogel structure and device performance. Finally, we discuss challenges in matrix design, triboelectric interfaces, and device integration. These design principles may guide durable multifunctional nanocomposite hydrogel-based TENGs for wearable electronics under repeated deformation and long-term on-skin operation.