High-resolution inkjet printing of conductive carbon nanotube twin lines utilizing evaporation-driven self-assembly

We report about the inkjet printing of multi-walled carbon nanotubes (MWCNTs) for conductive tracks. The MWCNTs were grown by chemical vapor deposition allowing a defined length and diameter. An inkjet-printable ink formulation was prepared by dispersing the MWCNTs in water. Inkjet-printed high resolution patterns were obtained by printing the prepared ink formulation on silicon wafers utilizing evaporation-driven self-assembly processes. After the deposition of the ink, the solvent evaporation induces material flows within the liquid moving the MWCNTs preferably to the edges of the printed patterns as well as to the print starting position where they assemble. Atomic force microscopy (AFM) reveals a preferential orientation of the deposited MWCNTs. The resulting deposit pattern is well-known as coffee-ring effect which is used here to enable high resolution printing and self-ordering of the MWCNTs. Depending on different print parameters such as drop spacing or substrate temperature, conductive track widths in the range of 5-15 μm were achieved with a electrical resistivity of about 3.9·10−3 to 5.6·10−3 Ω·m measured by current-sensitive AFM.