Light-Induced Fabrication of Patterned Conductive Nanocarbon Films for Flexible Electrode

A film forming method for patterned single-walled carbon nanotube (SWCNT) films was developed by applying photoisomerization of cationic azobenzene as a dispersant. By use of this method, micrometer-sized SWCNT patterned films were directly prepared on various substrates from SWCNT dispersions through short-term (5–120 s) ultraviolet (UV) irradiation. The film formation mechanism included the light-induced dispersibility change of SWCNT due to the detachment of the photoisomerized dispersant from SWCNT surfaces. Upon UV irradiation, a certain concentration of the SWCNT dispersion induced the gelation, which subsequently became a solid film. Using this method, we obtained a 40 μm SWCNT patterned film. The SWCNT film thickness was adjustable from tens of nanometers to over a micrometer. As the resultant SWCNT films contained only a small amount of impurities, the films showed superior electrical conductivity compared with SWCNT films fabricated through a general wet-coating process. Additionally, the electrical conductivity of the prepared SWCNT films was more thermally stable than the conductivity of the wet coated films as <5% decrease in their sheet resistance was observed after the thermal treatment at 200 °C for 1 h or 1 year of storage at room temperature. Therefore, the described method can be potentially used for manufacturing SWCNT flexible electrodes.