Solvent Evaporation Assisted Direct Ink Writing Using Polar Solvent for Flexible Polyvinyl Fluoride Piezoelectric Composites in Enhancement of Piezoelectric Properties

The fabrication of 3D printing piezoelectric polymer sensors has been of great importance due to their low-cost fabrication, phase manipulation, flexibility, and great piezoelectric response. In this study, a printable ink of polyvinylidene fluoride (PVDF) has been synthesized to enable the fabrication of flexible piezoelectric devices using solvent evaporation assisted direct ink writing (DIW). Different weight percentages of barium titanate (BTO) – 10 wt.%, 15 wt.%, and 20 wt.%, - along with 5 wt.% of multi-wall carbon nanotubes (MWCNT) in a polar solvent solution of dimethyl sulfoxide (DMSO), with a PVDF to solvent ratio of 1:5.23 have been used to fabricate piezoelectric polymer sensors aimed at enhancing the polar phase of PVDF and achieve a high piezoelectric coefficient. In addition, by using solvent evaporation assisted DIW, it is possible to align BTO and MWCNT with each depositing layer, which contributed to the promotion of the polar phase of PVDF and therefore increase their piezoelectric properties. The results from these 3D printed composites showed that a phase transition of PVDF from non-polar α-phase to a polar phase can be acquired by using temperature of 80 °C and an electric field of 3kV by contact poling. Under controlled temperature and humidity conditions, the proposed PVDF/BTO/MWCNT composite shrinks about 10% while maintaining its flexibility. Furthermore, by fabricating PVDF with 20 wt.% BTO obtained the optimal piezoelectric coefficient (d₃₃) of 53.25 pC/N, while maintaining its flexibility with a young modulus of 4.87MPa.