Effect of build orientation on all additively manufactured polyvinylidene fluoride with electrical poling for strain sensing and energy-harvesting application

The development of highly sensitive and flexible strain sensors is critical for applications in wearable technology, structural health monitoring, and energy-harvesting. Additive manufacturing (AM) presents a promising solution due to its ability to create sensors with complex geometries and tailored microstructures. However, optimizing the fabrication parameters to enhance the performance of these sensors remains a challenge. This study focuses on the fabrication of polyvinylidene fluoride (PVDF)-based piezoelectric strain sensors using the material extrusion (ME) process, investigating how different printing orientations and poling methods affect their mechanical and piezoelectric properties. PVDF was selected for its strong piezoelectric characteristics and was extruded and printed in three flat orientations: 0°, 45°, and 90°. To improve the β-phase content and enhance piezoelectric performance, two poling methods contact poling and corona poling were applied to the printed samples. Mechanical testing showed that the 45° printing orientation resulted in the highest Young's modulus (131.17 ± 2.25 MPa) and ultimate tensile strength (23.57 ± 0.76 MPa). However, strain-sensing tests revealed that the sample printed in the 0° orientation and subjected to corona poling exhibited superior performance, achieving a maximum output voltage of 11 V, a short circuit current of 0.9 µA, and a power output of 5.5 µW under 20% strain. This work demonstrates that the 0° printing orientation, combined with corona poling, optimizes the sensor's performance, offering both high sensitivity and effective energy-harvesting capabilities. The novelty of this research presents the systematic exploration of orientation and poling effects, advancing the understanding of AM in sensor fabrication and providing a foundation for developing more efficient and responsive piezoelectric devices. These findings not only contribute to the literature on AM of sensors but also open new avenues for the creation of multifunctional devices that can simultaneously act as sensors and energy harvesters, broadening their potential applications.