Effect of Fabrication Conditions on the Performance of Porous Polyviny- lidene Fluoride (PVDF) Piezoelectric Sensors under Compression

Abstract

Polyvinylidene Fluoride (PVDF) is a piezoelectric polymer that has many different applications and uses. Two measurable characteristics of PVDF films are the conformation of the polymer chain and the piezoelectric output. There has been little investigation on how different abrication factors can influence both characteristics. The goal of this study is to determine how different factors can have an effect on the chain conformation and the piezoelectric output of porous PVDF films. To fabricate the PVDF films, PVDF powder was dissolved in 2-butanone and 40 wt% of Zinc Oxide (ZnO) nanoparticles were added to the solution. Once the film was dried, the ZnO nanoparticles were dissolved using 10M hydrochloric acid to leave a mesoporous PVDF film. The fabrication factors studied were (1) the total sample weight of PVDF and ZnO, (2) the amount of 2-butanone solvent, and (3) the % solvent removed in the oven before air-drying. To determine the effect of the fabrication factors, the films were characterized mechanically via an instantaneous compressive load using a tensile tester and measuring the peak voltage generated, and structurally using Fourier Transform Infrared Spectroscopy (FTIR) to estimate the fraction of electroactive chain conformation. It was determined that the total amount of PVDF had a significant effect on the piezoelectric voltage output from the compression tests, while the amount of solvent affected the relative amounts of the different crystalline phases. Interestingly, normalizing the voltage output per PVDF mass shows diminishing returns in voltage generated with increasing amount of PVDF. Unexpectedly, no direct correlation between amount of electroactive chain conformation and the piezoelectric output was observed, which suggests other confounding factors (e.g., pore size distribution, PVDF network architecture) that may influence the piezoelectric voltage output.