Functionalized PDMS for regulating the triboelectric output of nanogenerators: a study of charge transfer mechanisms

Polydimethylsiloxane (PDMS) is one of the most widely used materials in triboelectric nanogenerators (TENGs) due to its remarkable flexibility and robustness, yet its triboelectric output often limits practical applications. In this study, we present a method for tuning the triboelectric properties of PDMS through surface functionalization using self-assembled monolayers of siloxane-based molecules. Our results demonstrate that the functionalized PDMS films exhibit distinct charge donating or withdrawing behaviours, confirmed by molecular simulations and experimental characterization. Notably, trimethylsiloxyphenylmethacrylate (TMSPMA) functionalized PDMS achieved the highest voltage of 189 +/- 6 V and current output of 6.75 +/- 0.26 mu A, leading to a 2-fold increase in peak power density compared with the standard PDMS. Moreover, to elucidate the charge transfer mechanisms between the functionalized PDMS and indium tin oxide (ITO) electrode, nanoanalytical techniques such as nano-Fourier transform infrared spectroscopy (nano-FTIR) and Kelvin probe force microscopy (KPFM) were employed to evaluate the surface chemical and electrical properties at the local scale. This research not only enhances the understanding of polymer/metal contact electrification, but also opens avenues for optimizing TENG efficiency through targeted surface functionalization strategies.