Liquid-solid triboelectric nanogenerators for a wide operation window based on slippery lubricant-infused surfaces (SLIPS)

Triboelectric nanogenerators (TENG) have emerged as suitable devices that are suitable to harvest widely abundant and renewable blue energy. However, a major drawback in related deployments include the reliability of the system when operating in variable atmospheric conditions. To address this limitation, we propose the integration of slippery lubricant-infused porous surfaces (SLIPS) as key TENG component. For instance, we combine SLIPS with transistor-inspired architectures to develop a robust single-electrode triboelectric nanogenerator (SLIPS-SE-TENG) that is shown to operate effectively under extreme temperature and humidity. For this purpose, we use the energy of water droplets (as in rain) impacting a surface to generate the electrical energy output. Our theoretical calculations and atomic force microscopy measurements show that a small volume of lubricant per surface area (4 μL/ per cm² of porous PTFE) is sufficient to produce a low water contact angle hysteresis, leading to efficient energy conversion, provided the droplet's moving velocity on the surface surpasses a threshold (0.3 mm/s). As such, we demonstrate SLIPS-SE-TENG to generate an instantaneous short-circuit current of 3 μA (charge density 8.8 nC/cm²). Importantly, we address the limitations of TENG fabricated with traditional superhydrophobic surfaces, affording a device that works normally and stably in harsh environments, under freezing temperatures or high humidity.