2, The University of Texas at El Paso, El Paso, Texas, United States
This study presents 3D printing and testing of pressure/strain/temperature sensor using poly(vinylidene) fluoride (PVDF), BaTiO3 (BT), and multiwall carbon nanotubes (MWCNTs) through the fused deposition modeling (FDM) 3D printing technique. PVDF polymer and BT ceramics are piezo-, pyro- and di-electric materials extensively investigated for sensor and energy storage/harvesting applications due to their unique characteristic of dipole polarization. However, when combined they rarely provide good piezoelectric performance due to the low coupling coefficient between their interfaces. In this study, MWCNTs were utilized to resolve the low coupling coefficient issue by dispersing MWCNTs in the PVDF matrix to create stress reinforcing network, dispersant, and electron conducting functions for BT nanoparticles. Moreover, due to high thermal conductivity characteristics of MWCNTs it can provide high thermal sensibility when subject to temperature change by influencing capacitance on nanocomposites. In addition, since MWCNTs and BT provide very high mechanical strength and strain respectively in PVDF matrix high change of poison ratio when subject to tensile force can be utilized to sense a strain as impact of capacitance and resistance. Various BT and MWCNTs percentages of nanocomposite film were fabricated by the FDM 3D printing which can simplify the fabrication process while providing lower cost and design flexibility. The increasing MWCNTs and BT particles gradually increase the piezoelectric coefficient (d31) by 129 pC/N with 0.4wt.%-MWCNTs/18wt.%-BT/PVDF. The measured d31 of the printed nanocomposites is comparable with pure BT ceramics or composites (79 ~ 185 pC/N). It was observed that 1wt.%-MWCNTs/12wt.%-BT/PVDF and 1.7wt.%-MWCNTs/60wt.%-BT/PVDF nanocomposites show highest strain and temperature sensibility. These results provide not only a technique to 3D print piezoelectric nanocomposites but also unique combination of BT and PVDF with MWCNTs for applications in multiple sensing application.