High-voltage-assisted FDM 3D printing of PVDF piezoelectric sensors for wearable applications

Polyvinylidene fluoride (PVDF) is a promising piezoelectric polymer with extensive applications in flexible electronics and human-machine interfaces. In this research, a fused deposition modeling (FDM) 3D printing technique is employed to fabricate PVDF films and piezoelectric sensors. An external high-voltage field is applied during printing to enhance β-phase formation and improve piezoelectricity. The rheological behavior of PVDF is systematically investigated using a rotational rheometer, confirming its shear-thinning nature, which is essential for smooth extrusion. Results indicated that viscosity decreased significantly with increasing shear rate, and temperature strongly influenced fluidity and solidification behavior. To optimize functional properties, the dielectric, ferroelectric, and piezoelectric responses of PVDF films under varying voltage conditions were analyzed. Films prepared at 2 kV exhibited superior surface quality, maximum remanent polarization, enhanced piezoelectric Strain coefficient (d33), and improved crystallization behavior, as confirmed by DSC, FTIR, and XRD analyses. Four flexible piezoelectric sensors were fabricated using a sandwich encapsulation method. The sensors demonstrated high sensitivity (113.32 mV/N), excellent linearity (0.9893), and strong stability over 11,600 pressing cycles. They exhibited reliable frequency response at 50, 100, and 200 Hz, with maximum output reaching 8.4 V during human motion detection, including walking, running, and jumping. This research validates the feasibility of integrating high-voltage-assisted FDM printing with PVDF to achieve enhanced piezoelectric sensors. Limitations remain in packaging design and physiological signal detection sensitivity. Future research will optimize printing paths, layer thickness, and hybrid-material integration to develop advanced, skin-conformal wearable devices for biomedical monitoring, rehabilitation, and intelligent sensing applications.