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Science 20 March 2009:
Vol. 323. no. 5921, pp. 1575 - 1578
DOI: 10.1126/science.1168312
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Research Articles

Giant-Stroke, Superelastic Carbon Nanotube Aerogel Muscles

Ali E. Aliev, Jiyoung Oh, Mikhail E. Kozlov, Alexander A. Kuznetsov, Shaoli Fang, Alexandre F. Fonseca, Raquel Ovalle, Márcio D. Lima, Mohammad H. Haque, Yuri N. Gartstein, Mei Zhang,* Anvar A. Zakhidov, Ray H. Baughman{dagger}

Improved electrically powered artificial muscles are needed for generating force, moving objects, and accomplishing work. Carbon nanotube aerogel sheets are the sole component of new artificial muscles that provide giant elongations and elongation rates of 220% and (3.7 x 104)% per second, respectively, at operating temperatures from 80 to 1900 kelvin. These solid-state–fabricated sheets are enthalpic rubbers having gaslike density and specific strength in one direction higher than those of steel plate. Actuation decreases nanotube aerogel density and can be permanently frozen for such device applications as transparent electrodes. Poisson's ratios reach 15, a factor of 30 higher than for conventional rubbers. These giant Poisson's ratios explain the observed opposite sign of width and length actuation and result in rare properties: negative linear compressibility and stretch densification.

The Alan G. MacDiarmid NanoTech Institute, University of Texas at Dallas, Richardson, TX 75083, USA.

* Present address: Department of Industrial Engineering, Florida State University, Tallahassee, FL 32306, USA.

{dagger} To whom correspondence should be addressed. E-mail: ray.baughman{at}utdallas.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)