Network Tunability of Natural Rubber Compositions Unlocks Partially Sustainable Triboelectric Nanogenerator

Triboelectric nanogenerators (TENG) have emerged as a promising candidate for sustainable energy harvesting; however, most materials used in TENG fabrication rely on petroleum-sourced polymers. Notably, a few studies have used sustainable materials, such as natural rubber (NR). In a filler-free system, the NR-TENG output is low. In most such cases, fillers were added to tune the NR-TENG properties. However, these fillers are not sustainable. Hence, it is critical to devise a strategy to improve the NR-TENG output under filler-free conditions. Herein, we report a filler-free strategy that leverages precise control over the sulfur network to enhance the NR-TENG output. The optimized sample demonstrated exceptional durability over 90 000 cycles, a power density of 4.53 W/m², and a short-circuit current of 23.2 µA, representing ∼700% and ∼300% enhancements over the best-reported NR-based systems. Mechanistically, performance is governed by the interplay between sulfur content and cross-link-driven deformation behavior. A theory-driven mathematical model was derived to predict TENG output and demonstrated strong agreement with experimental findings. The optimized TENG was pressure-sensitive, with a sensitivity of 0.035 V/kPa. As a prototype, the technology was applied to develop a self-powered boundary system that enables accurate, real-time sports monitoring with minimal reliance on human intervention.