Janus‐Structured TENG for Complex Dual‐Mode Communication Using Water Medium Across 200 m

Abstract Underwater communication using triboelectric nanogenerators (TENGs) offers key benefits such as independence from external power sources and immunity to water conditions, but faces challenges like short transmission range and single‐mode operation. This study presents a flexible, bifunctional Janus film as a high‐performance TENG for long‐distance underwater signal transmission. The PEDOT:PSS‐doped charge‐generating layer minimizes charge dissipation, while the PEDOT:PSS and BaTiO₃ enriched charge‐trapping layer enhances retention, ensuring robust performance in both contact and non‐contact modes. Dual‐mode transmission supports underwater tasks such as wireless switching, communication, charging, and gesture recognition with 94.84% accuracy. Remarkably, gesture signals transmitted over 200 m through a water pipe set a record for Maxwell's displacement current‐based communication. Additionally, a smart rescue system demonstrates the non‐contact mode's ability to self‐power SOS signal transmission through water pipes in emergency scenarios, unaffected by water quality or pipe shape. This work expands TENG applications in self‐powered, long‐range underwater communication.