Fluorinated-PDMS enhanced single-electrode triboelectric nanogenerator for biomechanical energy harvesting and sensing applications

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Abstract
Single-electrode triboelectric nanogenerators (STENGs) are promising candidates for biomechanical energy harvesting and self-powered sensing due to their simple structure and compatibility with wearable systems. However, their performance is often limited by the intrinsic tribonegativity of polymer friction layers. In this study, we report a facile surface chemistry approach to enhance the triboelectric performance of polydimethylsiloxane (PDMS) by fluorinated silane functionalization. PDMS films spin-coated on ITO/PET substrates were surface-functionalized using 1H, 1H, 2H, 2H-perfluorooctyl-trichloroethoxysilane (FOTES), introducing fluorine-rich –CF2 and –CF3 groups at the outermost surface. X-ray photoelectron spectroscopy confirmed successful fluorination, while Kelvin probe force microscopy revealed a significant reduction in surface potential, indicating enhanced electron-accepting capability and increased tribonegativity. As a result, the FOTES-functionalized PDMS STENG exhibited a substantial improvement in output performance, with the open-circuit voltage and short-circuit current increasing from ∼91.5 and ∼10 to ∼390 V and ∼65 μA, respectively, under hand-tapping conditions. The enhanced performance was further validated under controlled excitation (30 N, 4 Hz). The device demonstrated practical energy-harvesting capability through efficient rectification, capacitor charging, and instantaneous lighting of 240 commercial LEDs, achieving a maximum power density of 5.53 mW cm−2. In addition, the STENG functioned as a self-powered biomechanical motion sensor, capable of distinguishing different human motions such as clapping, clicking, and hammering based on distinct voltage signatures. This study demonstrates that fluorinated surface functionalization is an effective and scalable strategy to enhance triboelectric performance without increasing device complexity, offering strong potential for wearable energy harvesting and self-powered sensing applications.

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