Improving the actuating response of carbon nanotube/ionic liquid composites by the addition of conductive nanoparticles

Polyaniline (PANI) or carbon black (CB) was used as a conductive additive in porous electrodes of a dry-type carbon nanotube (CNT)-polymer actuator to improve the actuation properties. We estimated the strain from the bending motion of the actuator in the frequency range of 200-0.005 Hz. The generated stress was calculated from the Young's modulus of the electrode film and the maximum strain. Eight different types of electrode films were prepared by changing the mixed amount of PANI or CB into the CNT electrode film. When a same amount of PANI (50 mg) against CNT (50 mg) was added to the CNT electrode (in the case of CNT/PANI(50/50)), the strain of CNT/PANI(50/50) was increased to be almost three times larger than that of CNT(50) (without any additives). As a result, CNT/PANI(50/50) showed more than five times the generated stress compared to CNT(50). Using 40 mg of CB as an additive, CNT/CB(50/40) showed a more than four times larger stress compared to CNT(50). The electrochemical properties such as conductivity and capacitance were also investigated and discussed. An asymmetrical three-layered actuator element was fabricated to investigate the actuation mechanism. The results imply that the anode contracts and the cathode expands. (C) 2011 Elsevier Ltd. All rights reserved.