Zinc-air powered carbon nanotube yarn artificial muscle

Previously known electrochemically powered yarn artificial muscles that mimic the structure and function of natural muscles show remarkable performance in actuation stroke and work capacity. However, these electrochemical muscles are traditionally powered by a voltage source, which adds weight and volume to the system when constructing a microscale robot, making it challenging to achieve a compact design. Here, we demonstrate that carbon nanotube muscles are powered by a chemical source in the electrode and environmentally available oxygen. These muscles provide 15 times the gravimetric work capacity of natural skeletal muscle. These powerful muscles effectively operate as zinc-air batteries, which use a coiled carbon nanotube yarn as the muscle electrode. With the available zinc-air fuel cell generating voltage of 1.35 V, the maximum contractile stroke and work capacity are 5.17 % and 0.60 J/g, respectively. This muscle system can contract over 80 cycles with 5 milligrams of zinc, and by refueling or recharging the battery, the cycle life can be increased.