Self-sustaining humidity gradient in nanocellulose moist-electric transparent generator via hydrophilic-hydrophobic Janus interfaces

Moist-electric generation typically exploits water molecule diffusion or ionic concentration gradients, but constructing highly differentiated hydrophilic-hydrophobic surfaces for efficient power generation remains challenging. To address this, we developed a highly stable cellulose film matrix with superior moisture response via a dual-crosslinked strategy. Crucially, this achieves bionic in-situ calcification through forming a CaCO 3 surface layer. Sequentially, this robust matrix facilitates the creation of a stable hydrophilic-hydrophobic differential surface to fabricate a sandwich-structured LiCl/DNF/CaCO 3 -SiO 2 transparent film. The resulting thin film (40 μm) device sensitively detects ambient humidity changes. A single component achieves a sustained open-circuit voltage of 1.5  V . It can charge a 10 μF capacitor to 10 V within 1 h, powering small devices like light bulbs and calculators. The enhanced water contact angle difference of 131° between surfaces significantly boosts the humidity gradient and electrochemical output. This work demonstrates the feasibility of powering small electronics and provides a novel pathway for green, high-performance energy-harvesting film devices and lightweighting units.