Twisted polymeric and CNT yarn-based actuators and energy harvesters

M. Dias Lima
LINTEC of America,
United States

Keywords: actuators, carbon nanotube yarns, energy harvesthing

Summary:

Carbon nanotube (CNT) films can be used as starting material for a variety of products such as electrically conductive layers, filtering membranes and for manufacturing of fiber and yarns (1). LINTEC have developed dry and liquid based methods to produce large size, free standing films of CNTs which can have an aligned or random orientation, reaching areal densities as low as 0.2 microg/cm2 (only 2x of single layer of graphene). Their volumetric density can be as low as 1mg/cm3 (close to air) still with a weight normalize tensile strength greater than high strength steel (2). Perhaps the most interesting application for CNT films is the production of CNT yarns through spinning. Addition of guest materials during the spinning process produces unique yarns with the guest material content as high as 99%wt (3,4). It has been demonstrated (5) that highly twisted carbon nanotube yarns can perform as mechanical actuators, capable to generate impressive tensile actuation, providing large strokes and vastly exceeding the work and power capabilities of natural skeletal muscle. By applying electrical pulses, contractions up to 50% and a mechanical work capacity of 1.36 kJ/kg were achieved, which exceed by two orders the performance of biological muscle (6). More than a million cycles of actuation were performed without significant loss of performance. These actuators also can operate as torsional motors: a single fiber can rotate heavy rotors at speeds higher than 70 000 RPM (7). Finally, besides of producing mechanical work from electric energy CNT yarns can be use for the opposite purpose. Mechanical energy harvesting using CNT yarns which are thin and flexible enough to be incorporated into conventional textiles have been shown to directly convert tensile elastic energy into electrical energy (8). That makes a very attractive energy source for wearable electronics by directly harvesting mechanical energy from the natural movements of the human body. 1. Baughman R.H., et al. Science 297 (2002) 787 2. Lima, M.D., et al. Science 338 (2012) 928 3. Liu, Z.F., et al. Science. 349, (2015) 400 4. Lima, M.D., et al. Science 331 (2011) 51 5. Lima, M.D., et al. Science 338 (2012) 929 6. Lima, M.D., et al. Small 11 (2015) 3113 7. Kim S.H., et al. E.& E. Science 8 (2015) 3336 8. Kim S.H., et al. Science 357 (2017) 773