Electrical and electromechanical characteristics of self-assembled carbon nanotube thin films on flexible substrates

We report the fabrication and characterization of layer-by-layer self-assembled single-walled carbon nanotube (SWNT) thin films on plastic substrates. The SWNT multilayers are alternating layers of SWNTs and poly(dimethyldiallylammonium chloride) (PDDA). The SWNTs are deposited on the pre-patterned gold electrodes and measured as thin-film resistors. The resistance of the SWNT thin film decreases when the number of assembled SWNT layers increases. The SWNT layers are modeled as a set of resistors in parallel with a "base" resistor and "layer" resistors. The flexibility of the polymer substrate allows high bending angles. We discovered that increasing the substrate bending angle greatly decreases the resistance of the SWNT thin film. For thin-film resistors (length: 2.8 cm) containing 14 and 16 SWNT layers, the resistance changes are measured as -38.2% and -47.1% at a bending height of 1 cm. The observed "piezoresistive" phenomenon of the assembled SWNT thin films creates opportunities for highly sensitive sensors and electronic devices in many areas.