A Single Additive Enables 3D Printing of Highly-Loaded Iron Oxide Suspensions.

A single additive, a grafted copolymer, is designed to ensure the stability of suspensions of highly-loaded iron oxide nanoparticles (IOPs) and facilitate 3D printing of these suspensions in the filament form. This poly (ethylene glycol) (PEG)-grafted copolymer of N-[3(dimethylamino)propyl]methacrylamide (DMAPMA) and acrylic acid (AA) harnesses both electrostatic and steric repulsion to realize an optimum formulation for 3D printing. While used at 1.15 wt. % (by the weight of IOPs), the suspension attains ~81 wt. % solid loading-96% of the theoretical limits as calculated by the Krieger-Dougherty equation. Rectangular, thick-walled toroidal, and thin-walled toroidal magnetic cores and a porous lattice structure are fabricated to demonstrate the utilization of this suspension as an ink for 3D printing. The electrical and magnetic properties of the magnetic cores are characterized through impedance spectroscopy (IS) and vibrating sample magnetometry (VSM), respectively. The IS indicates the possibility of utilizing wire-wound 3D printed cores as the inductive coils. The VSM verifies that the magnetic properties of IOPs before and after the ink formulation are kept almost unchanged due to the low dosage of the additive. This particle-targeted approach for the formulation of 3D printing inks allows embodiment of a fully aqueous system with utmost target material content.