Electro‐Induced Mechanical and Thermal Responses of Carbon Nanotube Fibers

Carbon nanotubes (CNTs) have been extensively studied since their discovery because of their unique structure and remarkable mechanical, electrical, and optical properties. In order to improve their practical applications, great effort has been made to assemble CNTs into one-, two-, and three-dimensional (1D, 2D, 3D) forms, such as continuous fi bers, fl exible fi lms, and vertically aligned arrays, using a bottom-up approach. [ 1,2 ] Particularly, 1D CNT fi bers composed of highly aligned CNTs well retain the excellent properties of the individual tubes. [ 3–11 ] For example, CNT fi bers are much stronger and stiffer than various engineering fi bers, [ 12,13 ] with a tensile strength and toughness higher than ca. 2.5 GPa and 60 J g −1 , respectively. [ 6,14,15 ] Their electrical conductivities are up to 10 3 S cm −1 and can be further remarkably improved by various post-spin treatments such as acid treatment, anodization, and deposition of metal nanoparticles. [ 16–18 ] Recently, the effi cient conversion of electrical energy into mechanical energy (i.e., an electromechanical actuator) has been achieved using CNT fi bers. [ 11,19 ] In a CNT fi ber actuator there is usually a simultaneous occurrence of a lengthwise contraction and a rotary torsion upon applying an electric current, due to Ampere’s law for aligned CNTs. [ 11 ]