Polymer-Assisted 3D Printing of Inductor Cores

Abstract

Poly(glycerol monomethacrylate) (PGMA) prepared by reversible addition−fragmentation chain transfer polymerization was investigated as an additive for high-loading iron oxide nanoparticle (IOP) 3D printable inks. The effect of adjusting the molar mass and loading of PGMA on the rheology of IOP suspensions was investigated, and an optimized ink formulation containing 70% w/w IOPs and 0.25% w/w PGMA 98 at pH 10 was developed. This ink was successfully 3D printed onto various substrates and into several structures, including rectangles, high aspect ratio cylinders, letters, spiral-and comb-shaped structures, and thin-and thick-walled toroids. The effect of sintering on the mechanical properties of printed artifacts was investigated via four-point flexural and compressive testing, with higher sintering temperatures resulting in improved mechanical properties due to changes in the particle size and microstructure. The printed toroids were fabricated into inductors, and their electrical performance was assessed via impedance spectroscopy at a working frequency range of 0.001−13 MHz. There was a clear trade-off between electrical properties and sintering temperature due to a phase change between γ-Fe 2 O 3 and α-Fe 2 O 3 upon heating. Nevertheless, the optimized devices had a Q factor of ∼40 at 10 MHz, representing a superior performance compared to that of other inductors with iron oxide cores previously reported. Thus, this report represents a significant step toward the development of low-cost, fully aqueous, high loading, and 3D printable ceramic inks for high-performance inductors and functional devices.

Multifunctional Self-Assembled Block Copolymer/Iron Oxide Nanocomposite Hydrogels Formed from Wormlike Micelles

“…However, DLS studies of 0.1% w/w IOP dispersions indicated that some aggregates remained after dispersion of the IOP power in water. 48 Additionally, TEM images obtained for pristine IOPs also suggest the presence of aggregates on dispersion into water at high dilutions ( Figure S4 ). Nevertheless, after sufficient high-speed mixing with copolymer at low temperature, the Fe 2 O 3 /G 62 –H 170 dispersions formed a stable viscous fluid, and the IOPs did not separate from the dispersion under the application of a strong magnetic force.…”

“…In this prior study, the mean diameter of these IOPs was determined to be 29 ± 9 nm by SEM. However, DLS studies of 0.1% w/w IOP dispersions indicated that some aggregates remained after dispersion of the IOP power in water . Additionally, TEM images obtained for pristine IOPs also suggest the presence of aggregates on dispersion into water at high dilutions (Figure S4).…”

“…γ-Fe 2 O 3 soft magnetic nanoparticles from a commercial source were chosen for use in this investigation as they have lower coercivity, higher electrical resistivity, and good thermal stability when compared to other kinds of IOPs. − In addition, we recently reported the preparation of high solids dispersions of these IOPs for 3D printing using the same high-speed mixer and PGMA as a polymeric additive . In this prior study, the mean diameter of these IOPs was determined to be 29 ± 9 nm by SEM.…”

“…Nevertheless, after sufficient high-speed mixing with copolymer at low temperature, the Fe 2 O 3 /G 62 –H 170 dispersions formed a stable viscous fluid, and the IOPs did not separate from the dispersion under the application of a strong magnetic force. Given that PGMA is a nonionic and water-soluble polymer which has pendant 1,2-diol functional groups, it is anticipated that this polymer has the capability to adsorb onto the surface of IOPs through hydrogen bonding and the formation of a five-membered chelate ring with Fe, , thus helping to disperse the IOPs during mixing.…”

“… 45 − 48 In addition, we recently reported the preparation of high solids dispersions of these IOPs for 3D printing using the same high-speed mixer and PGMA as a polymeric additive. 48 In this prior study, the mean diameter of these IOPs was determined to be 29 ± 9 nm by SEM. However, DLS studies of 0.1% w/w IOP dispersions indicated that some aggregates remained after dispersion of the IOP power in water.…”