Poly­(vinylidene fluoride) (PVDF) possesses outstanding piezoelectric properties, which allows it to be utilized as a functional material. Being a semicrystalline polymer, enhancing the piezoelectric properties of PVDF through the promotion of the polar β phase is a key research focus. In this research, precipitation printing is demonstrated as a scalable and tailorable approach to additively manufacture complex and bulk 3D piezoelectric energy harvesters with high-β phase PVDF. The β-phase fraction of PVDF is improved to 60% through precipitation printing, yielding more than 200% improvement relative to solvent-cast PVDF films. Once the precipitation-printed PVDF is hot-pressed to reduce internal porosity, a significant ferroelectric response with a coercive field of 98 MV m–1 and a maximum remnant polarization of 3.2 μC cm–2 is observed. Moreover, the piezoelectric d 33 and d 31 coefficients of printed then hot-pressed PVDF are measured to be −6.42 and 1.95 pC N–1, respectively. For energy-harvesting applications, a stretching d 31-mode energy harvester is demonstrated to produce a power density of up to 717 μW cm–3, while a printed full-scale heel insole with embedded d 33-mode energy harvesting is capable of successfully storing 32.2 μJ into a capacitor when used for 3 min. Therefore, precipitation printing provides a new method for producing high-β phase PVDF and bulk piezoelectric energy harvesters with the advantages of achieving geometry complexity, fabrication simplicity, and low cost.

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Over the last several decades, additive manufacturing (AM) has been primarily used for rapid prototyping or to create novel geometries that would be difficult or impossible to create by normal manufacturing methods. More recently, research has been focused on expanding the list of materials that can be made through additive manufacturing, opening a greater range of material properties for this manufacturing method. Due to the unusual conditions during AM, including the high cooling rates and voxel by voxel method of production, AM parts often have anisotropic material microstructures and properties. In this investigation, the laser power, composition, and nozzle head speed during direct metal deposition of copper-iron alloys was varied to understand how the grain structure within the printed parts could be changed and controlled. The resulting dendrite spacing was measured and compared to calculated cooling rates from Gaussian beams on flat plates under similar material and laser properties, which resulted in a cooling rate to dendrite spacing relationship following an inverse square root, as is found in other dendritic systems [Young and Kerkwood, Metall. Trans. A 6, 197–205 (1975)]. Thus, it is demonstrated that in the Cu-Fe system, dendrite spacing can be controlled through manipulation of printing parameters.

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