Inkjet Printing of Magnetic Particles Toward Anisotropic Magnetic Properties

Abstract

Unique properties of one-dimensional assemblies of particles have attracted great attention during the past decades, particularly with respect to the potential for anisotropic magnetism. Patterned films can be created using inkjet printing; however, drying of particle-laden colloidal droplets on solid surfaces is usually accompanied by the well-known coffee-ring effect, deteriorating both the uniformity and resolution of the printed configurations. This study examines the effect of externally applied magnetic field on particle deposition patterns. Ferromagnetic Gd5Si4 particles were formulated in terpineol oil and directly deposited via magnetic field-assisted inkjet printing on a photopaper to generate patterned films with suppressed coffee-ring effect. The particle deposition morphology is determined by both solvent imbibition and particle-magnetic field interactions. Three characteristic times are considered, namely, the critical time for solvent imbibition into the substrate (tim), the time it takes for particles to form chains in the presence of the magnetic field (tch), and the time in which the particles reach the substrate in the direction normal to the substrate (tpz). The characteristic time ratios (tpz/tim) and (tpz/tch) determine the final deposition morphology in the presence of magnetic field. The ability to control particle deposition and assembly, thus tuning the magnetic anisotropic properties of nanostructured materials is a promising approach for many engineering applications.

Rheology-Assisted Microstructure Control for Printing Magnetic Composites—Material and Process Development

“…The area enclosed by the hysteresis curve for measurements along the direction of particle structuring is greater by approximately 5% compared to the hysteresis curve obtained for the direction perpendicular to the direction of field structuring. The present observations and findings are congruent with results in the technical literature for magnetic composites with aligned magnetic fillers [ 33 , 44 ]. This enhancement further confirms the alignment of the easy axis of magnetization of individual particles by orienting the fillers, resulting in the chain-like microstructures.…”

“…During the process of magnetic particle structuring under an external magnetic field, the dispersed magnetic particles experience forces that are a function of several parameters, i.e., magnetic, gravity, and viscous drag forces. The particle motion is expressed mathematically in Equation (10) [ 32 , 33 , 34 , 35 ]. where the individual force terms are expressed as indicated in the following equations: …”

3D Printing‐Enabled Nanoparticle Alignment: A Review of Mechanisms and Applications

“…Typically, particle size that influences flowability is less than 5 μm, 1/100 smaller than the nozzle sizes, and the concentration is less than 10 wt%. [34,35,205,206] Many research reports have established the flowassisted alignment physics of anisotropic particles in free liquid micro jets and emerging microdroplets. For example, based on in situ Xray and microscopic analyses, the nozzle dimensions, liquid flow, and particle aspect ratios were the most critical parame ters in determining anisotropic particles' flow orientation [207][208][209] Inkjet has been a great tool in surface patterning and can deposit particles at selective locations, including CNTs and graphene layers.…”

“…[388] So far, the coupling of the magnetic field with inkjet printing has effectively aligned parti cles of iron oxide (Fe 3 O 4 ), [5] PEGcoated Fe 3 O 4 [173] strontium fer rite (SrFe12O19), [142] and, Gd5Si4. [206,389] The materials manufactured from magnetic fieldassisted 3D printing are more often than not wellpatterned structures instead of containing wellaligned particles oriented individu ally along with specific directions. Current research in this area has focused on magnetic particles that can assist the printing procedure.…”

“…[543] Similarly, conventional uses by adding mag netic fields around material containers may need careful con trol over the particle types, particle concentrations, and their interactions to the overall magnetic field (Figure 25e 1 -e 9 ). [544] As a comparison, 3D printing can locally deposit materials responsive to external magnetic fields before subsequent mate rial addition, [142,206,389,545] e.g., the alignment of iron oxide at dif ferent locations in microneedles (Figure 25f 1 ,f 2 ). [545] In this way, the nanoparticles at each printing voxel can be different, and the whole printing part can contain voxels of varying material compositions, particle morphologies, and properties.…”