Moist‐Electric Wallpaper With Engineered Unidirectional Moisture Transport for Indoor Energy Harvesting and Humidity Management

ABSTRACT Moist‐electric generators (MEGs) convert ambient humidity into electricity, but their inherently low power output makes outdoor deployment as a general energy source impractical. Indoor environments, where humidity is stable and low‐power electronics demand only microwatt‐to‐milliwatt supplies, present a more realistic opportunity—and wallpaper, with its large continuously exposed surface area and seamless architectural integration, is the most compelling platform to realize it. Here we report the first wallpaper‐type MEG, enabled by a peripheral‐absorption, center‐evaporation architecture that achieves engineered unidirectional moisture transport on a single paper sheet. Glycerol at the periphery captures atmospheric moisture; polyvinylpyrrolidone in the intermediate region acts as a bound‐water sink whose reduced porosity and lowered water activity drive inward transport through Laplace pressure and chemical potential gradients; and a wax‐treated center exploits the phase‐selective behavior of hydrophobic pores—blocking liquid while transmitting vapor—to confine evaporation without a solid seal. A concealed through‐hole interconnection strategy enables modular scaling with no visible wiring. A single unit delivers ∼0.34 V and ∼2.2 µW/cm 2 at 80% RH with stable output over 90 min. A 1596‐unit array powers a wireless keyboard and simultaneously reduces indoor humidity from 38% to 32%, transforming passive wall surfaces into self‐powered, climate‐responsive interfaces.