The production of large scale ultrathin aligned CNT films by combining AC electric field with liquid flow

We report a simple and versatile technique combining the use of an AC electric field with a liquid shear force to prepare ultrathin aligned CNT films on solid substrates. Multiwalled carbon nanotubes (MWCNTs), which were synthesized by a template method and acid-treated single walled carbon nanotubes (SWCNTs) were dispersed in water and used for the ultrathin film fabrication. A solid substrate was immersed in the CNT dispersions and withdrawn at constant speed under AC electric field. SEM images of the substrate showed that CNTs were aligned with the AC electric field and the withdrawal direction and formed uniform films with a thickness around 10 nm for SWCNTs and 90 nm for MWCNTs. Repeating the deposition process increases the density and size of the film while also maintaining nanometer-scale thickness. Unidirectional alignment of CNTs was also confirmed by Raman spectra and electric conductivity measurements. It was found that ultrathin films of aligned SWCNTs exhibited very high anisotropic electrical conductivity with conductivity measured parallel to the alignment direction 3.3 x 10(5) times higher than that measured in the perpendicular direction. We demonstrate that use of the aligned ultrathin SWCNT film for a unidirectional alignment of liquid crystal. (C) 2013 Elsevier Ltd. All rights reserved.