Powerful, Large Stroke Electrochemical Carbon Nanotube Yarn Artificial Muscles

Success in making artificial muscles that are faster, more powerful, and provide larger strokes would expand their applications. Electrochemical carbon nanotube yarn muscles are of special interest because of their relatively high energy conversion efficiencies. However, they are bipolar, meaning that they do not monotonically expand or contract over the available potential range. Also, their stoke monotonically decreases with increasing actuation frequency. Our new unipolar stroke carbon nanotube yarn muscles solve these problems, since muscle stroke changes between extreme potentials are additive and muscle stroke increases with increasing potential scan rate. The normal decrease in stroke with increasing scan rate is overwhelmed by a major increase in effective ion size. Enhanced muscle strokes, contractile work-per-cycle, contractile power densities, and energy conversion efficiencies are obtained for unipolar muscles. Our sheath-run artificial muscles will also be described, which use a carbon nanotube sheath on a coiled polymer fiber to drive remarkable electrochemical actuation. These discoveries resulted from a collaborative effort with many scientists around the world.