Fully Printable Manufacturing of Miniaturized, Highly Integrated, Flexible Evaporation-Driven Electricity Generator Arrays.

Harvesting sustainable clean energy from natural water evaporation holds great promise to provide continuous power for portable and wearable electronics. However, poor portability and complex fabrication processes hinder the low-cost and large-scale integration of flexible evaporation-driven electricity generators (FEEGs). Herein, a fully-printed flexible evaporation-driven generator (PFEEG) is developed. Utilizing custom-formulated functional inks, the asymmetric structures, current collectors, and hygroscopic water storage units can be manufactured by a patternable, scalable, and layer-by-layer deposition technique of screen printing. Thus, a PFEEG unit (0.5 cm × 1 cm × 38 µm) can generate a voltage of ≈0.8 V over a wide relative humidity (RH) range from 20% to 90%, and a maximum power density of 1.55 µW cm at 70% RH. An array of 200 PFEEGs connected in series or parallel can produce voltages up to 152.41 V or a current up to 1.02 mA. Furthermore, the scalable PFEEG array can not only be seamlessly connected with the printed flexible circuit but can also be integrated with a humidity sensor and display arrays to form a self-powered printed flexible sensing system. This work presents a practical strategy for continuous power supply of portable and wearable electronics.