Field effect enhanced electric double layer for high-output droplet energy harvester

The underlying principle of droplet energy generation, which involves contact electrification and droplet-based electricity, has gained significant traction in converting raindrop energy in recent years. The efficiency of power harvesting is highly dependent on the contact area, requiring the droplet to spread maximally across the device's surface. However, other droplet dynamics, such as sliding and dripping, have been underutilized in previous research. In this work, we introduce a novel design that leverages the field effect to enhance electric double layer for high output droplet energy harvester, capturing both negative and positive charges to generate electricity. Additionally, electrons produced during the contact electrification process can be stored on a floating electrode within the device, creating a high electrical potential that further enhances electricity generation through the electric double layer capacitance at the water-metal interface. Remarkably, without the need for pre-charging or grounding the top electrode, this field effect enhanced droplet energy harvesting can achieve voltages exceeding 430 V and currents over 1 mA using a 60 μL tap-water droplet. Moreover, our device demonstrates continuous energy harvesting during sliding motion, highlighting its potential for large-scale applications, such as in panel configurations. The novel mechanism and technology presented in this work offer significant advancements in the understanding and practical implementation of droplet energy harvesting.