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An abstract of the article "High-performance Torsional and Tensile Carbon Nanotube Yarn Composite Muscles," by M. Lima and colleagues is presented.

Hybrid polypyrrole (PPy)-multi walled carbon nanotube (MWNT) yarns were obtained by chemical and electrochemical polymerization of pyrrole on the yarn surface. The material was characterized by SEM imaging, electrochemical, mechanical and electrical measurements. It was found that the hybrid PPy-MWNT yarns possess significantly higher mechanical strength (over 740 MPa) and Young's modulus (over 54 GPa) and than the pristine MWNT yarn. The material also exhibited substantially higher electrical conductivity (over 23500 S/m). Specific capacitance for PPy-MWNT yarn was found over 60 F/g. Measurements of temperature dependences of electrical conductivity revealed metallic behaviour at high temperature and semiconducting behaviour at low temperature with the metal-to- insulator transition near 100 K. The collected low temperature data are in the good agreement with variable range hopping model (3DVRH). The improved durability of the yarns is important for electrical applications. The composite yarns can be produced in commercial quantities and used for the applications where the electrical conductivity is of primary importance. [ABSTRACT FROM AUTHOR]