D₂O-Enhanced Twistron Yarn Harvesters for Low-Frequency Mechanical Energy Harvesting

Twistrons, spun yarns made from carbon nanotubes, convert mechanical energy into electricity through stretch-induced yarn densification. However, improving their low-frequency harvesting performance remains a key challenge for wearable electronics and environmental applications. Here, we report that replacing H₂O with D₂O in neutral aqueous electrolytes significantly enhances twistron harvesting performance. Compared to H₂O-based systems, the peak power in D₂O-based systems increased by up to 2.5 times and the maximum energy per cycle improved by 1.8 times in the low-frequency range of 0.01-2 Hz. The energy conversion efficiency reached 9.5%, which is higher than any other previously reported twistron harvester operating in neutral electrolytes. Additionally, our harvesters provided higher power output and energy per cycle than previously reported non-twistron, material-based harvesters over the frequency range of 2-50 Hz. Mechanistic analysis attributes this enhancement to slower charge redistribution dynamics and a higher initial double-layer capacitance in D₂O-based electrolytes. To demonstrate practical applicability, we developed a wearable energy harvesting textile and a thermal energy harvester powered by a yarn harvester coupled with a high-spring-index thermal muscle and used a harvester array to charge supercapacitors and power wearable electronics. These results highlight the potential of D₂O-based twistrons as high-performance platforms for efficient energy harvesting in diverse scenarios, including human motion, environmental temperature fluctuations, and ocean waves.