Effect of Nanoparticles Coating and Solvent Selection on the Structure of PVDF/CoFe 2 O 4 Composites Fabricated by Direct Ink Writing

ABSTRACT This study investigates how solvent selection and polyethylene glycol (PEG) coating of cobalt ferrite (CFO) nanoparticles affect the morphology and phase composition of polyvinylidene fluoride (PVDF)/CFO composite films fabricated by direct ink writing (DIW). A custom DIW printer was developed to enable controlled extrusion of PVDF‐based inks containing bare or PEG‐coated CFO nanoparticles and prepared with either N,N‐dimethylformamide (DMF) or an acetone/dimethyl sulfoxide (Ac + DMSO) solvent system. Bare CFO increased spherulite size and reduced the electroactive PVDF phase content in both solvent systems. In contrast, PEG‐coated CFO combined with Ac + DMSO improved nanoparticle dispersion and increased the electroactive phase fraction in the composite from 42% to 50%. These results show that solvent selection and nanoparticle surface modification jointly govern the structure of DIW‐printed PVDF/CFO composites and identify Ac + DMSO with PEG‐coated CFO as the most promising formulation for magnetoelectric applications.