Tribological Enhancement of Triboelectric Nanogenerator Based on Lubrication

Triboelectric nanogenerators (TENGs) have emerged as promising devices for harvesting ambient energy from various sources. TENGs convert environmental energy into electricity, making them suitable for a wide range of applications, particularly in miniaturized electronics and wearable devices. The operational principle of TENGs relies on the generation of electricity through electric charge-induced potential and triboelectrification. Despite their practicality and cost-effectiveness, TENGs face significant challenges related to abrasive wear at solid-solid contacts, which can substantially impact their operational lifespan. To address these limitations, researchers have developed lubricant-based TENGs. This novel approach not only mitigates friction and wear but also enhances electrical output by suppressing air-breakdown phenomena and reinforcing surface charges on the triboelectric layer. Our study focused on evaluating the tribological behavior and electrical outputs of representative polymers in TENGs when combined with non-polar lubricants. This comprehensive analysis aims to contribute to the development of more durable and sustainable lubricant-based TENG system for energy harvesting.
We evaluated the tribological performance of various representative polymers when lubricated with non-polar lubricants. The findings revealed a complex relationship between lubricant viscosity and the tribological behavior of the polymers. We observed a non-linear trend where friction coefficients and wear loss initially decreased with increasing viscosity but subsequently increased at higher viscosities. This relationship underscores the multifaceted interactions within lubricant-based TENG systems. To understand this phenomenon, we utilized the Hersey number to estimate lubricant film thickness. This analysis demonstrated the crucial role of lubricant viscosity in determining film thickness, which in turn governs the dominant lubrication regime and, consequently, the tribological behavior. Our research also uncovered significant impacts of polymer wettability and wear-resistance on tribological behavior under lubrication. Polymers exhibiting high wettability demonstrated an increased sensitivity to lubricant viscosity in terms of friction coefficients. Additionally, polymers characterized by high wear resistance exhibited lower friction coefficients and reduced wear, attributed to smaller contact areas when lubricated. A key finding of our study was the significant enhancement in mechanical durability of lubricant-based TENG systems when utilizing non-fully wetted and wear-resistant polymers in combination with viscous lubricants. This synergistic combination proved particularly effective in extending the lifespan of the tribological system. To explore practical applications, we evaluated a lubricant-engaged TENG device. The results were highly promising, demonstrating that the use of a non-fully wetted and wear-resistant polymer under a viscous lubricant led to enhanced long-term electrical output. This improvement can be attributed to the prevention of material failures through the mitigation of wear and the suppression of air-breakdown.
Our study provides a comprehensive examination of the tribological and triboelectric characteristics of polymers in lubricant-engaged TENG system. We found that non-polar lubricants induce viscosity-dependent tribological behavior in polymers, significantly affecting lubricant film thickness and lubrication regimes. Furthermore, we established that polymer wettability and mechanical properties play crucial roles in influencing lubricant accessibility and contact area. The combination of non-fully wetted, wear-resistant polymers with viscous lubricants proved to enhance both tribological and triboelectric performance significantly. Our findings contribute valuable insights to the design of mechanically reliable and sustainable TENG systems with extended lifespans and superior triboelectric performance.