Charge-induced electrochemical actuation of armchair carbon nanotube   bundles
  The effects of charge doping on the structural deformation and on the electronic structure of armchair single wall carbon nanotube (SWNT) bundles are investigated through first-principles calculations. In particular, we select a (6; 6) SWNT as an example and we calculate a mechanical deformation in the SWNT bundles as a function of gate voltage, which could serve as a basis of the electromechanical actuators in an artificial muscle. We find that the magnitudes of the actuation responses such as strain and stress of the (6; 6) SWNT bundle in the case of hole doping are substantially larger than those of electron doping. The (6; 6) SWNT bundle also exhibits a low-symmetry and opens an energy band gap of about 0.41 eV around the charge neutral condition, which allows a semiconductor-to-metal transition in the electron-doping regime when the relative shift of the Fermi energy goes up to 0.60 eV, above which the Young modulus increases. 
Nguyen T. Hung, Ahmad R. T. Nugraha, Riichiro Saito
cond-mat.mtrl-sci