Poly(vinylidene fluoride) (PVDF) and its copolymers are the polymers with the highest dielectric constants and electroactive responses, including piezoelectric, pyroelectric and ferroelectric effects. This semicrystalline polymer can crystallize in five different forms, each related to a different chain conformation. Of these different phases, the β phase is the one with the highest dipolar moment and the highest piezoelectric response; therefore, it is the most interesting for a diverse range of applications. Thus, a variety of processing methods have been developed to induce the formation of the polymer β phase. In addition, PVDF has the advantage of being easily processable, flexible and low-cost. In this protocol, we present a number of reproducible and effective methods to produce β-PVDF-based morphologies/structures in the form of dense films, porous films, 3D scaffolds, patterned structures, fibers and spheres. These structures can be fabricated by different processing techniques, including doctor blade, spin coating, printing technologies, non-solvent-induced phase separation (NIPS), temperature-induced phase separation (TIPS), solvent-casting particulate leaching, solvent-casting using a 3D nylon template, freeze extraction with a 3D poly(vinyl alcohol) (PVA) template, replica molding, and electrospinning or electrospray, with the fabrication method depending on the desired characteristics of the structure. The developed electroactive structures have shown potential to be used in a wide range of applications, including the formation of sensors and actuators, in biomedicine, for energy generation and storage, and as filtration membranes.

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The electroactive β-phase of poly(vinylidene fluoride) (PVDF) can be nucleated by introducing CoFe 2 O 4 nanoparticles within the polymer matrix, leading to electroactive materials with large potential for sensor and actuator applications. The effects of the CoFe 2 O 4 nanoparticle electrostatic charge on the phase crystallization of PVDF polymer is reported. For this purpose, CoFe 2 O 4 nanoparticles were coated with anionic (SDS), nonanionic (Triton X-100), and cationic (CTAB) surfactants, and the obtained coated nanoparticles were used as fillers. It is found that the piezoelectric β-form of the polymer increases when CoFe 2 O 4 nanoparticles with higher negative electrostatic charge are added. This behavior is attributed to the interaction between the negatively charged magnetic particles and the polymer CH 2 groups, having a positive charge density. Further the relationship between the β-phase content and the piezoelectric response has been demonstrated. The magnetostriction of the ferrite nanoparticles and the proven piezoelectricity of the polymer allows the use of the material in piezoelectric and magnetoelectric sensors or/and actuators.

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Poly(vinylidene fluoride) (PVDF) microparticles have been produced by electrospraying as a suitable substrate for tissue engineering applications. The influence of the polymer solution concentration and processing parameters, such as electric field, flow rate and inner needle diameter, on microparticle size and distribution has been studied. Polymer concentration is the most influential parameter on PVDF microparticle formation. Higher concentrations promote the formation of fibers while dilute or semi dilute concentrations favor the formation of PVDF microparticles with average diameters ranging between 0.81 AE 0.34 and 5.55 AE 2.34 mm. Once the formation of microparticles is achieved, no significant differences were found with the variation of other electrospray processing parameters. The electroactive b-phase content, between 63 and 74%, and the crystalline phase content, between 45 and 55%, are mainly independent of the processing parameters. Finally, MC-3T3-E1 cell adhesion on the PVDF microparticles is assessed, indicating their potential use for biomedical applications.