Researchers have developed a groundbreaking method to transform ordinary cotton fabric into a self-sustaining electricity generator that harvests energy from atmospheric humidity. By applying specialized polymer coatings, the fabric creates a continuous moisture gradient that drives ion transport, allowing it to power small electronic devices and LED lights both day and night. This innovation represents a significant step forward in sustainable wearable technology, offering a battery-free power source that remains functional through movement and washing while requiring no external charging.
The new technology, categorized as a photothermal evaporation-driven moisture generator (PEMG), utilizes the natural properties of cotton fibers enhanced by two specific polymers: polypyrrole and polydopamine. These materials possess contrasting chemical and optical characteristics that are essential for maintaining a steady electrical output. Polypyrrole is highly efficient at converting light into heat, which accelerates water evaporation, while polydopamine reflects more light and retains moisture longer.
The researchers engineered an asymmetrical structure by coating only half of the polypyrrole-treated fabric with polydopamine. This design ensures that one side of the material remains damp while the other dries rapidly, creating a persistent moisture gradient. This difference in humidity levels forces ions to move through the microscopic channels of the cotton fibers, generating a stable flow of electricity without the need for external power sources or traditional batteries.
During laboratory testing, a series of six fabric units produced a voltage of 1.18 V under standard solar intensity and 0.72 V during nighttime conditions. This was sufficient to keep white LED bulbs illuminated for more than 24 hours. The manufacturing process involves immersing untreated cotton into a pyrrole monomer solution to create a conductive black layer, followed by a treatment in an alkaline dopamine solution to form a thin, light-interfering film that gives the fabric a distinct purple hue.
Beyond stationary use, the material shows immense potential for the wearable electronics sector. When integrated into clothing, such as a vest, the fabric can utilize human sweat to supplement ambient humidity, significantly boosting its voltage output during physical activity. The energy harvested is capable of charging capacitors and running wireless audio equipment. Furthermore, the fabric proved resilient in mechanical trials, maintaining its performance after being subjected to friction, repeated bending, and standard washing cycles.
Environmental conditions also play a role in the system’s efficiency. The research team noted that acidic moisture and certain dissolved salts can enhance electron transfer and increase voltage, as protons serve as highly effective charge carriers. Because the system relies on common environmental factors and requires no recharging, it offers a durable and flexible alternative to rigid power storage solutions.