Magnetic Ferrite Nanoparticle Inks for Syringe Printable Inductors

Additive manufacturing has the potential to simplify fabrication processes by using a single apparatus that exchanges printable material at the print head to create complex shapes. Circuit components can be made of various materials such as magnetic materials, which are specifically used for many applications, including inductors. Few syringe printable magnetic inks have been explored, and even fewer to create a final product with high magnetic content compared to polymer content (>90 vol %). In this study, syringe printable, colloidal magnetic inks are made using both iron oxide and MnZn doped ferrite nanoparticles by stabilizing them with poly(acrylic acid) (PAA) and adding a free polymer poly(ethylene oxide) (PEO) of various molecular weights and glycerol to control ink viscosity and evaporation rates. Printability is further explained using complex rheology. MnZn doped ferrite inks are printed into toroids and sintered at 1400 °C to increase magnetic permeability. A sintered toroid is constructed into an inductor device and characterized using a Vector Network Analyzer (VNA), which exhibits an inductance of 4.26 μH at 8.5 MHz. This study lays out a template for ferrite inks with the potential to be fabricated into useful passive electronic devices.