Piezoelectric Outputs of Electrospun PVDF Web as Full-Textile Sensor at Different Mechanical Excitation Frequencies

Abstract

With the increasing application of electrospun PVDF webs in piezoelectric sensors and energy-harvesting devices, it is crucial to understand their responses under complex mechanical excitations. However, the dependence of the piezoelectric effect on mechanical excitation properties is not fully comprehended. This study aims to investigate the piezoelectric output of randomly oriented electrospun PVDF nanofiber webs fabricated through different electrospinning processes at various mechanical excitation frequencies. The electrospun PVDF web was sandwiched between two textile electrodes, and its piezoelectric output as a full-textile sensor was measured across a frequency range from 0.1 Hz to 10 Hz. The experimental results revealed that the piezoelectric output of the electrospun PVDF web exhibited a nearly linear increase at excitation frequencies below 1.0 Hz and then reached an almost constant value thereafter up to 10 Hz, which is different from the hybrid PVDF or its copolymer web. Furthermore, the dependency of the piezoelectric output on the excitation frequency was found to be influenced by the specific electrospinning process employed, which determined the crystalline structure of electrospun PVDF nanofibers. These findings suggest that determining an appropriate working frequency for randomly oriented electrospun PVDF nanofiber webs is essential before practical implementation, and the piezoelectric response mode in different mechanical activation frequency ranges can be used to detect different human physiological behaviors.

Keywords: PVDF web; electrospinning conditions; frequency; mechanical excitation; piezoelectric outputs.

Figure 1

(a) A schematic representation of the full-textile pressure sensor and (b) a schematic diagram of the self-made experimental setup for piezoelectric characterization.

Figure 2

The real-time force and piezoelectric output of the packaged full-textile sensor prototype at different mechanical excitation frequencies: (a) 0.3 Hz; (b) 1.0 Hz. The sensitive material of the sensor prototype was obtained at an applied voltage of 20 kV; (c) the time-dependent activation force; (d) the piezoelectric output under the dynamic activation force.

Figure 3

The dependence of piezoelectric output on the mechanical excitation frequency. The full-textile sensor prototype is the same as that in Figure 2.

Figure 4

The effect of the excitation frequency on the output of PVDF nanofiber webs under different electrospinning conditions as full-textile sensors. (a) applied voltage; (b) feeding flow rates; (c) needle-tip diameter.