This study deals with investigations of mechanical, thermal, morphological and 4D (shape memory, magnetic and piezoelectric) properties of the feedstock filaments prepared for fused filament fabrication (FFF) process by twin-screw compounding of polyvinylidene difluoride (PVDF) reinforced with Mn doped ZnO. The Mn doped ZnO was synthesized by using sol-gel method up to the solubility limit (at first stage) so that the properties of the host, as well as dopant ions, are present in the composition. In the second stage, PVDF composite feedstock filaments reinforced with Mn doped ZnO nanoparticles have been prepared for FFF of biosensor/biomedical sensors/actuators. The results are supported by scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), differential scanning calorimetry (DSC) observations. The results of this study suggest that the optimum set of process parameters for tensile properties is combination of pre-heat treatment, 210 ℃ barrel temperature, 3 % Mn-ZnO loading, and 0.15N.m screw torque. Also the reinforcement of Mn-ZnO in PVDF has led to improved piezoelectric, magnetic, and shape memory properties.