High-Throughput Top-Down Fabrication of Uniform Magnetic Particles

Abstract

Ion Beam Aperture Array Lithography was applied to top-down fabrication of large dense (108–109 particles/cm2) arrays of uniform micron-scale particles at rates hundreds of times faster than electron beam lithography. In this process, a large array of helium ion beamlets is formed when a stencil mask containing an array of circular openings is illuminated by a broad beam of energetic (5–8 keV) ions, and is used to write arrays of specific repetitive patterns. A commercial 5-micrometer metal mesh was used as a stencil mask; the mesh size was adjusted by shrinking the stencil openings using conformal sputter-deposition of copper. Thermal evaporation from multiple sources was utilized to form magnetic particles of varied size and thickness, including alternating layers of gold and permalloy. Evaporation of permalloy layers in the presence of a magnetic field allowed creation of particles with uniform magnetic properties and pre-determined magnetization direction. The magnetic properties of the resulting particles were characterized by Vibrating Sample Magnetometry. Since the orientation of the particles on the substrate before release into suspension is known, the orientation-dependent magnetic properties of the particles could be determined.

Externally controlled on-demand release of anti-HIV drug using magneto-electric nanoparticles as carriers

“…In the experiments described below, for the role of MENs we used nanoparticles made of the popular core-shell composition CoFe 2 O 4 @BaTiO 3 , in which the relatively high moment CoFe 2 O 4 1-nm shell was used to enhance the ME coefficient 18 . In general, nanoparticles as small as 5 nm in diameter can be fabricated with physical methods such as ion beam proximity lithography or imprint lithography 19 . In this study, considering the novelty of the approach, we focused on the main discovery of using MENs for on-demand drug release rather than on the development of scaling approaches.…”

Magnetic-Assisted Treatment of Liver Fibrosis

“…The “bottom-up approach” starts from metal ions in solution via chemical methods and is probably the most commonly used strategy. The top-down approach starts with bulk material, which is further processed, i.e., by laser ablation [72,73,74,75,76] or lithography [77,78,79] including that of nanospheres [80]. The lithography techniques have broad control on the shape of nano or microstructures; however, the scaling of this method to large-scale production was reported to be challenging [81].…”

Collecting a swarm in a grid environment using shared, global inputs

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