A furan-maleimide based 3D printing ink for the fabrication of a self-healing and high strength thermoset with recycling potential.

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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