Photo-mechanical actuation of carbon nanotubes: mechanisms and applications in micro and nano-devices

We review the current state of the art in photomechanical actuation of carbon nanotubes and their composites. The article presents key points in the photomechanical responses of carbon nanotubes and show how orientation, alignment and anisotropic optical properties of carbon nanotubes influence photomechanical actuation. The current state of the field of carbon-nanotube polymer photomechanical actuators is presented. The photomechanical responses of nanotube-polymer systems depend on the structure of the actuator, nanotube alignment, entanglement and the presence of pre-strains in the sample. While the mechanism of photomechanical actuation is not fully understood, we discuss some possible mechanisms that contribute to the overall photomechanical responses of carbon nanotubes and their polymer composites. It is expected that the interplay between elastic, electrostatic, polaronic and thermal interactions give rise to the overall photomechanical responses of carbon nanotubes. We also discuss some insights into how the photo-mechanical responses of the carbon nanotubes and their polymers may be coupled to the band structure of carbon nanotubes. Finally, we review the applications of photomechanical actuation of carbon nanotube in Micro-Electro-Mechanical Systems (MEMS) and nanotechnology.