Stabilization of permalloy nanoparticles for syringe printable inductors

Additive manufacturing has the potential to fabricate custom parts with complex shapes. For syringe printing, there is a possibility for printing filaments consisting of different materials on a single tool. Additively manufactured electronics is a major field of investigative research, where filaments contain nanoparticles to tailor properties, such as metal to improve magnetic permeability. This study investigates syringe printing parts with high magnetic permalloy (Ni80Fe20) nanoparticle content (>35 vol%) and the properties of inductors printed from these inks. Two different metal alloy particle sizes of 250 nm and 30 nm are synthesized to observe the effect of particle size on stability. Zeta potential and settling behavior are observed to discern how coating procedures enhance particle stability in water. Permalloy nanoparticle inks are concentrated with polyethylene glycol (PEG) to increase viscosity and glycerol to decrease evaporation rates while printing. It is found that PEG and glycerol stabilize 30 nm permalloy nanoparticles in addition to increasing ink viscosity. Permalloy nanoparticle inks are printed into toroid shapes demonstrating the feasibility of fabricating useful three-dimensional magnetic structures. These inductors exhibited an inductance of 180 nH at 30 MHz.