Double-Walled Carbon Nanotubes Ink for High-Conductivity Flexible Electrodes

Carbon electronics is a growing field that spans printable electronics, energy storage devices, and biosensors. The commercialization of these carbon-based technologies requires a scalable production of high-conductivity, acid-free carbon nanotube ink dispersions. Superacids have been used to achieve high-concentration CNT inks; however, a scalable acid-free process to achieve similar concentrations has been missing for a long time. In this work, we demonstrate that water and sodium cellulose are sufficient for achieving a scalable production of highly conductive CNT-based ink, provided the solution is processed through a very high-shear microfluidizer. Materials used in this process are acid-free and require no postprocessing, such as centrifuging or heating. We have achieved conductivity and sheet resistance of (3.6 ± 0.2) × 105 S m–1 and 0.11 Ω □–1 mil–1, respectively, which are among the best reported values for any undoped carbon-based film. The thermal conductivity of the free-standing carbon films is 43 ± 4 W m–1 K–1. By use of this method, uniformly dispersed CNT inks of viscosity >1 Pa·s are produced. Once printed on paper, these CNT films show pronounced resilience to mechanical deformation. This simple but scalable process provides a viable technology for using carbon-based conducting inks for printing large-scale devices.