Multifunctional microparticles with uniform magnetic coatings and tunable surface chemistry

Abstract

Microplatelets and fibers that can be manipulated using external magnetic fields find potential applications as miniaturized probes, micromirrors in optical switches, remotely actuated micromixers and tunable reinforcements in composite materials. Controlling the surface chemistry of such microparticles is often crucial to enable full exploitation of their mechanical, optical and sensorial functions. Here, we report a simple and versatile procedure to directly magnetize and chemically modify the surface of inorganic microplatelets and polymer fibers of inherently non-magnetic compositions. As opposed to other magnetization approaches, the proposed non-aqueous sol-gel route enables the formation of a dense and homogeneous coating of superparamagnetic iron oxide nanoparticles (SPIONs) on the surface of the microparticles. Such coating provides a suitable platform for the direct chemical functionalization of the microparticles using catechol-based ligands displaying high affinity towards iron oxide surfaces. By adsorbing for example nitrodopamine palmitate (ND-PA) on the surface of hydrophilic magnetite-coated alumina platelets (Fe 3 O 4 @Al 2 O 3 ) we can render them sufficiently surface active to generate magnetically responsive Pickering emulsions. We also show that microplatelets and fibers coated with a uniform iron oxide layer can be easily manipulated using low magnetic fields despite their intrinsic non-magnetic nature. These examples illustrate the potential of the proposed approach in generating functional, magnetically responsive microprobes and building blocks for several emerging applications.

Bioinspired Nacre‐Like Ceramic with Nickel Inclusions Fabricated by Electroless Plating and Spark Plasma Sintering

“…[27] The results showed an improvements in strength (70%) and toughness (90%) relative to the control samples. [29] An extrusion process was recently reported for fabrication of bioinspired ceramic-metal composites, with high ceramic content. [27] Recently, alumina platelets pre-coated with another ceramic (titania) were used for investigation of the role of mineral nanointerconnectivity in nacre-like composites.…”

“…[28] Pre-coated ceramic micro-platelets may offer new opportunities in the field of bioinspired composites. [29] An extrusion process was recently reported for fabrication of bioinspired ceramic-metal composites, with high ceramic content. [21,25] However, the microstructure of this composite is composed of coarse layers of ceramic (%100-200 μm).…”

Recent Progress in Biomimetic Additive Manufacturing Technology: From Materials to Functional Structures

“…The combination of magnetic field with 3D printing was developed as 3D magnetic printing, which was successfully used to build bioinspired architectures inspired by bone, mollusk shells and mantis shrimp ( Figure a) . The alignments of magnetic response particles (decorated with superparamagnetic iron oxide nanoparticles) in the reactive resin were controlled by magnetic field . The particle orientation can either be strengthened or weakened in individual voxels depending on whether the alignment is parallel (local hardening) or perpendicular (crack steering) to the loading direction.…”

3D Assembly of Graphene Nanomaterials for Advanced Electronics

“…Alternative methods of coprecipitation use microwave irradiation to trigger the reaction . Others have explored the sol–gel synthesis (Figure b), or the attachment of preformed iron oxide by electrostatics (Figure c) . As graphitic particles are hydrophobic and without surface charge, electrostatic adsorption is done using intermediate polyelectrolytes such as proteins or polymers .…”