The primary goal of this project was to develop a flexible transparent conductor with 100 Omega/sq and 90% transmittance in the wavelength range of 400-700 nm on a. flexible substrate. The best result achieved so far was 110 Omega/sq at 88% transmittance using purified single-walled carbon nanotubes (SWNTs) coated on a polyethylene naphthalate (PEN) substrate. The secondary goal was to simplify the overall coating procedure; we successfully reduced the process from. five (prior art method) to three steps utilizing a sonication method. We also found that the use of metallic SWNTs significantly improved the conductivity and transmittance compared with the use of mixed SWNTs, i.e., unseparated SWNTs. Furthermore, a possible adhesion mechanism between SWNTs and the surface of PEN was studied; we concluded that a pi-pi stacking effect and a hydrophobic interaction are the major contributing factors for SWNTs to adhere to the surface of the substrate. (C) 2009 Elsevier B. V. All rights reserved.