Carbon Nanotube Inkjet Printing for Flexible Electronics and Chemical Sensor Applications

Abstract

Carbon nanotubes (CNTs) are becoming a promising new material for use in many fields including the field of electronics. Their mechanical and electrical properties lend themselves to be used in a new generation of electronic devices, namely flexible electronics. Although many deposition methods for carbon nanotubes exist, inkjet printing offers many advantages including superior patterning ability and low-cost fabrication. Presented in this work is the use of inkjet printing in order to deposit carbon nanotubes onto a flexible transparency film. The methods for developing and printing an aqueous single-walled carbon nanotube (SWCNT) ink and an aqueous multi-walled carbon nanotube (MWCNT) ink are discussed in detail. The carbon nanotubes are dispersed using sodium n-dodecyl sulfate (SDS), an anionic surfactant. It is discovered that the SDS:CNT ratio plays a crucial role in determining the conductivity of the printed carbon nanotube network. Thus, methods for optimizing this ratio are presented. To the author’s knowledge, this is the first report of carbon nanotube ink optimization regarding the ratio of dispersant concentration to carbon nanotube concentration. Additionally, the sheet resistance and transparency of the inkjet-printed carbon nanotube films are discussed. Incredibly conductive carbon nanotube networks were printed, reaching as low as 132 Ω/☐ for SWCNTs and 286 Ω/☐ for MWCNTs for 35 prints. These values are among the lowest reported sheet resistance values for carbon nanotube inkjet printing. Finally, the fabrication of a fully printed electrochemical sensor using inkjet-printed carbon nanotube electrodes is presented. The sensor was characterized using cyclic voltammetry, and the results confirm that inkjet-printed carbon nanotubes are indeed a candidate for use as flexible electrodes.