Effect of orientation on the piezoresistivity of mechanically drawn single walled carbon nanotube (SWCNT) thin films

Mechanically drawn SWCNT thin films were prepared and systematically investigated for understanding the effect of SWCNT orientation on the piezoresistive response of SWCNT thin film based piezoresistive sensors. Through polarized Raman spectroscopy analysis and coupled electrical–mechanical test, a quantitative relationship between the piezoresistive sensitivity and SWCNT alignment order parameter was established. This along with the morphological characterization, film area and sheet resistance measurement allow identifying the critical roles of SWCNT orientation, packing density, and micro-crack formation in dictating the piezoresistivity of mechanically drawn SWCNT thin film strain sensors. As compared to the randomly oriented SWCNT thin film sensor, the one with draw ratio of 3.2 exhibited 6 times increase on the gauge factor.