Twist-Based Refrigeration, Actuation, and Mechanical Energy Harvesting Using Twisted, Coiled, and Plied Yarns

Higher efficiency, lower cost refrigeration is needed for both large- and small-scale cooling. We show that high cooling results from twist changes for twisted, coiled, or supercoiled fibers, including those of natural rubber, NiTi, and polyethylene fishing line. By using opposite chiralities for twist and coiling, supercoiled natural rubber fibers and coiled fishing line fibers result that cool when stretched. Similar mechanics involving twist transfer between yarn twist and coiling are here used to make compact, energy-efficient refrigerators, thermal and electrochemical artificial muscles, and twistron electrochemical mechanical energy harvesters. For harvesting between 2 and 120 Hz, our most recent twistron carbon nanotube harvesters have higher gravimetric peak power and average power than previously reported for any prior-art, material-based mechanical energy harvester.