A flexible sensing device based on a PVDF/MWCNT composite nanofiber array with an interdigital electrode

This study reports the electrospinning of polyvinylidene fluoride (PVDF) piezoelectric nanofiber array on an interdigital (IDT) electrode to fabricate a flexible sensing device. This sensing device can convert the mechanical energies of low-frequency ambient vibrations and impacts into electrical signals. A mixed solution of PVDF and multi-wall carbon nanotube (MWCNT) was filled in a metallic needle injector that was connected with a high voltage of 1200 V. When the PVDF droplet in the needle tip was subjected to a high electric field, an extremely fine PVDF fiber can be spun out. The electrospun fibers were collected orderly using an X-Y stage. In the electrospinning process, the fiber was polarized and transformed into the piezoelectric beta-crystalline phase. PVDF/MWCNT crystallization as spherical composite structures can enhance the piezoelectric properties of PVDF fibers. Photolithography and etching processes were used to fabricate an IDT electrode with a gap of 100 mu m on a flexible polyimide (PI) substrate. The PVDF fiber array was packaged with epoxy/PI film. The packaged PVDF fiber array was repolarized in a high electric field of approximately 7V/mu m to increase d(33) mode conversion efficiency. The comparison of the analytical solution of the composite plate equation and the experimental results shows that the device can generate a peak voltage and current of 20.2 mV and 39 nA under 6 Hz vibration. In addition, at an impact testing at 15 Hz, the peak voltage of 24.4 mV with a current of 130 nA can be obtained. (C) 2014 Elsevier B.V. All rights reserved.