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.