Autonomous energy scavenging from the ambient environment is gaining attention as it offers a solution to the energy problems of numerous IoT devices. Recently, water-based energy harvesters have been developed due to their simplicity and eco-friendliness. However, these devices typically require periodic water supplementation, limiting their practicality. To address this, we created a transpiration-driven electrokinetic power generator (TEPG) with an artificial hydrological cycle to generate electricity continuously. Using carbon-coated cotton fabric, the TEPG generates power from a few drops of water (0.2 mL) by exploiting the potential difference in the asymmetrically wetted device and the pseudostreaming current. Unfortunately, the device ceases to function after an hour due to water evaporation. To ensure continuous operation, we integrated calcium chloride (CaCl2) to collect ambient water vapor and replenish the TEPG. In relative humidity (RH) levels of 15–60%, CaCl2 successfully compensates for water loss, sustaining electrical power generation. Moreover, CaCl2 enhances voltage (0.74 V) and current (22.5 μA) by supplying Ca2+ ions to the carbon surface, reducing device resistance. This self-operating TEPG (STEPG) is stable enough to power an LED for a week and charge a supercapacitor (5 F) to 1.6 V over eight days.-Scientific Journal cover design by scapiens

https://pubs.rsc.org/en/content/articlelanding/2020/ee/c9ee02616a#!divAbstract