From Electrical to Fuel Powered Artificial Muscles
M.E. Kozlov, J. Oh, T. Mirfakhrai, M. Zhang, S. Fang, J.P. Ferraris, J.D.W. Madden, R.H. Baughman
University of Texas at Dallas, US
Keywords: carbon nanotubes, artificial muscles, actuation
Abstract:A number of materials ranging from carbon nanotube yarns and sheets to shape memory alloys (SMA) have been explored for the application in the area of artificial muscles (actuators). It was found that if powered electrically, the isometric stress generated by nanotube actuators could be as large as 12 MPa. This approaches the stress generation capability of commercial ferroelectrics and is significantly larger than that of natural muscles. We also demonstrated several types of artificial muscles that convert the chemical energy of high–energy-density fuels to mechanical energy. The first type stores electrical charge and uses changes in stored charge for mechanical actuation. In contrast with electrically powered electrochemical muscles, only half of the actuator cycle is electrochemical. The second type of fuel-powered muscle provides a demonstrated actuator stroke and power density comparable to those of natural skeletal muscle and generated stresses that are over a hundred times higher. In this device the chemical energy in the fuel is converted to heat by a catalytic reaction of a mixture of fuel and oxygen in the air. The resulting temperature increase causes contraction of a shape memory metal muscle wire that supports this catalyst. Because of more than 30 times higher energy density obtainable for fuels like methanol, compared to that for the most advanced batteries, the major expected benefits are dramatic increase in energy conversion efficiency, work capacity, power performance. Application opportunities of Fuel Powered Artificial Muscles are diverse, and range from robots and morphing air vehicles to dynamic Braille displays and muscles powered by the fuel/air mixtures.