Flexible Graphitized Polyacrylonitrile Nanofiber Bundles for Strain Sensors

This work reports the use of graphitized Polyacrylonitrile (PAN) nanofiber bundle for strain sensing applications. Strain sensors employing piezoresistive properties of carbon nanofiber is relatively new compared to conventional piezoelectric electrospun nanofiber based devices. The graphitization of PAN nanofiber bundles annealed at 500°C, 750°C, and 950°C are studied by means of spectroscopic analysis techniques including Raman and X-ray photoelectron spectroscopy (XPS). The nanofiber bundle annealed at 750°C exhibits disordered (D) and ordered (G) peaks similar to the nanofiber bundle annealed at 950°C. This is confirmed by XPS analysis which shows the asymmetric C1s peak at 284.8 eV. Raman analysis has also been performed on the as-spun, stabilized and annealed samples to show the change in D and G peaks. Finally, a strain sensor utilizing the nanofiber bundle annealed at 950°C is fabricated which is sensitive enough to detect overall bending of less than 3° without the use of any external amplifier circuit.