Electrostatic Assembly of Self-Encapsulated Composite Electrets for High-Stability Droplet Energy Harvesting

Abstract Electret materials are vital for low-frequency mechanical energy conversion; however, their practical outdoor deployment is severely restricted by moisture-induced charge decay and environmental screening. Herein, an electrostatic assembly technology is reported to construct a robust composite electret film featuring a self-encapsulated inner charge layer. By bringing a corona-charged fluorinated ethylene propylene (FEP) film into intimate contact with an uncharged secondary dielectric layer, interfacial charge redistribution and dielectric polarization establish a persistent interfacial electric field, generating a maximum interfacial shear holding strength of 3.50 N/cm2. Following this electrostatic assembly via corona-injected charges, the resulting self-encapsulated structure effectively shields the active charge carriers from moisture and screening. Based on this film, a composite droplet electret generator (C-DEG) is developed. Utilizing a transistor-like “bulk effect”, the C-DEG delivers a peak power of 0.25 mW at a 2 MΩ load under a single-droplet impact, maintaining a stable output for over 6000 s. This work provides a stable, packaging-free paradigm for resilient self-powered systems.