Scalable Hygroscopic Moisture‐Electric Generator With Long‐Term Stability for Self‐Powered Wound‐Healing Stimulation

The growing demand for sustainable energy solutions has increased interest in ambient energy harvesters capable of continuous operation under diverse environmental conditions. Here, we report a hygroscopic moisture-electric generator (HMEG) that achieves long-term, self-sustained power generation through an asymmetric architecture composed of montmorillonite and calcium chloride. The integration of hygroscopic materials within a perforated coin-cell structure enables directional moisture transport and persistent ionic gradients, producing a stable open-circuit voltage of 0.55 V and a short-circuit current of 74 µA for 30 days at 50% relative humidity. The device delivers a maximum power density of 3.582 µW cm^- ² and exhibits strong scalability, with a large-area HMEG (7 × 7 cm²) producing 0.64 V and 816 µA for three days. A ten-unit array further outputs 5.5 V and 670 µA, confirming modular energy-harvesting capability. Beyond power generation, a single HMEG enabled in vitro electrical stimulation of L929 fibroblast cells, enhancing wound-healing-related behaviors. The stimulated group showed a 152% increase in cell-covered area on day 3 and 241% on day 5, along with elevated metabolic activity (32.1% and 23.4%). These results establish a durable and biocompatible platform linking moisture-driven energy harvesting with regenerative bioelectronics.