Electroactive properties and biological applications of electrospun PVDF polymer

摘要

PVDF is a piezoelectric polymer, exhibiting direct and inverse piezoelectric effect, with leading electroactive properties. This material is interesting for building energy transmission and harvesting systems, converting mechanical energy into electrical energy, such as electrospun PVDF sensors. However, only a few reports have shown inverse piezoelectric effect of electrospun PVDF. In this project the electrospinning technique was used to prepare PVDF nanofiber mat scaffolds for tissue engineering. The main objective is the preparation of electroactuated devices for mechanical stimulation of cells. Crystal phase ratios and morphology of the PVDF fiber mats were characterized by attenuated total reflectance Fourier transform infrared (FTIR/ATR) spectroscopy and scanning electron micrograph (SEM). For a better understanding of the differences between polar and non-polar PVDF, and of the effect of the electric field on the fibers’ composition, quantum mechanics and molecular dynamics calculations were performed. Several devices were prepared from assemblies of PVDF fiber meshes and conductive ink electrodes, with different geometries. The devices’ electrical impedances were measured as a function of frequency. Finally, the in vitro biocompatibility of the PVDF fiber meshes was tested. The results revealed that electrospinning parameters have significant effects on the crystal phase ratio and structure. As it was expected, the electrical impedance of PVDF decreased with the increase of β crystal phase ratio, as required for the piezoelectric behaviour of the PVDF fibers. The results also illustrated that the impedance of PVDF fibers mesh assemblies changed with varying shape, thickness, the geometric alignment of the fibers and the distance between conductive ink electrodes. The molecular simulations were able to predict the α to β phase change which results on partially poled fibers. In vitro cytocompatibility tests of PVDF scaffolds shown that PVDF fibers were not cytotoxic to the NIH/3T3 cells which meant PVDF fiber scaffolds can be used for cell stimulation.