Devices that convert electrical energy to mechanical (actuators) contain electroactive polymers which change shape or size in an electric field. Many electroactive polymers contain carbon nanotubes (CNTs) to ensure conductivity.

Brian Wardle and co-workers, MIT, USA, have shown that by utilizing aligned CNTs with high fraction packing, electroactive devise performance can be substantially improved. The improvements come from having a continuous path in the form of conduction channels, reduced electrical resistance and enhanced strain along the actuation direction.

The actuator had a three-layer structure with vertically aligned CNTs in a porous nanocomposite forming the electrodes. Accumulation of excess ions at one electrode and depletion at the other created actuation strain of 8 % under 4 V with fast actuation speed and no observed degradation over 10 min. of testing at 0.5 Hz.

• High Electromechanical Response of Ionic Polymer Actuators with Controlled-Morphology Aligned Carbon Nanotube/Nafi on Nanocomposite Electrodes
  S. Liu, Y. Liu, H. Cebeci, R. Guzmán de Villoria, J.-H. Lin, B. L. Wardle, Q. M. Zhang,
  Adv. Funct. Mater. 2010, 20, 3266–3271.
  DOI: 10.1002/adfm.201000570