Stearic Acid-Enhanced Triboelectric Nanogenerators with High Waterproof, Output Performance, and Wear Resistance for Efficient Harvesting of Mechanical Energy and Self-Powered Sensing for Human Motion Monitoring

Low power density and poor wear resistance seriously hinder the application of a triboelectric nanogenerator (TENG) in daily environments. However, current research has mainly focused on improving the performance of TENGs through inorganic fillers while neglecting the important property of wear resistance. Due to the excellent properties of stearic acid (SA), such as its cheap and easy availability, high electronegativity, wear resistance, hydrophobicity, and lubricity, as well as promoting the formation of electroactive beta phase polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), SA can be used as an organic multifunctional filler to improve the electrical output performance and wear resistance of TENG while increasing its hydrophobicity. In this work, we doped SA into polytetrafluoroethylene (PTFE)/PVDF-HFP matrix by solution casting method and template method to form SA-doped PTFE/PVDF-HFP(SA-PTFE/PVDF-HFP) composite polymer film, which were assembled with silk to form SA-TENG. Most importantly, the addition of 3 wt % SA not only increases the voltage and current of TENG by 3.7 times and 3.6 times, respectively, but also reduces the coefficient of friction and the amount of wear of TENG by 40.8 and 87.5%, respectively, and increases the hydrophobic angle by 12 to 133(degrees), which ensures the long-term and stable operation of TENG in different environments. In addition, SA-TENG can not only harvest energy from the surrounding environment and charge portable electronic devices but can also be used as a self-powered sensor to monitor human movement. This study not only provides a feasible strategy for organic fillers to solve the bottleneck problem of TENG application but also broadens the application scenarios of TENG.