Magnetic Field Alignment of Randomly Oriented, High Aspect Ratio Silicon Microwires into Vertically Oriented Arrays

Beardslee, Joseph A.; Sadtler, Bryce; Lewis, Nathan S.

doi:10.1021/nn304180k

Cited by 17 publications

(24 citation statements)

References 37 publications

(47 reference statements)

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“…Establishment of such a method would allow scientists to more efficiently exploit the anisotropic properties of MOFs through crystal alignment. Such anisotropically‐shaped particles, when magnetized, experience a magnetic torque to align the long‐axis of the particles along the direction of an applied magnetic field . NH 2 ‐MIL‐53(Al) MOF microneedles, which were prepared through coordination modulated growth, were selected as an example of a MOF with crystal shape and lattice anisotropy for this work.…”

Section: Figurementioning

confidence: 99%

Magnetic Control of MOF Crystal Orientation and Alignment

Cheng

Marshall

Young

et al. 2017

Chemistry A European J

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Most metal-organic frameworks (MOFs) possess anisotropic properties, the full exploitation of which necessitates a general strategy for the controllable orientation of such MOF crystals. Current methods largely rely upon layer-by-layer MOF epitaxy or tuning of MOF crystal growth on appropriate substrates, yielding MOFs with fixed crystal orientations. Here, the dynamic magnetic alignment of different MOF crystals (NH -MIL-53(Al) and NU-1000) is shown. The MOFs were magnetized by electrostatic adsorption of iron oxide nanoparticles, dispersed in curable polymer resins (Formlabs 1+ clear resin/ Sylgard 184), magnetically oriented, and fixed by resin curing. The importance of crystal orientation on MOF functionality was demonstrated whereby magnetically aligned NU-1000/Sylgard 184 composite was excited with linearly polarized 405 nm light, affording an anisotropic fluorescence response dependent on the polarization angle of the excitation beam relative to NU-1000 crystal orientation.

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Section: Figurementioning

confidence: 99%

Magnetic Control of MOF Crystal Orientation and Alignment

Cheng

Marshall

Young

et al. 2017

Chemistry A European J

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“…Functional devices based on vertical cylinder arrays are generally produced by top‐down methods, i.e., growth or etching . Bottom‐up, self‐assembly approaches are being explored for generating these types of structures due to interest in reducing fabrication costs and expanding the materials used for both cylindrical components (wires or tubes) and underlying substrates . A key challenge for assembling these anisotropic particles into vertical arrays is that they typically favor orientations with long axes parallel rather than perpendicular to the surface …”

Section: Introductionmentioning

confidence: 99%

“…A variety of strategies show promise for assembly of vertical arrays. These include applied fields (electric and magnetic), controlled drying, other solution‐phase assembly methods, and specially designed, segmented particles . In most cases, relatively small particles (i.e., nanorods ≤20 nm wide and ≤100 nm long) have been used in these studies, thus requiring interrogation by electron microscopy after drying.…”

Section: Introductionmentioning

confidence: 99%

“…Methods relying on applied fields or controlled drying have generated well‐oriented nanorod arrays, in some cases over relatively large areas (>1 cm 2 ), but generally require stringent control over assembly conditions . Much larger microparticles (length >1 μm) have also been assembled to form vertical arrays . Real‐time imaging of particles during the assembly process is possible for these larger particles, which are also closer to the dimensions used in top‐down device structures .…”

Section: Introductionmentioning

confidence: 99%

“…Much larger microparticles (length >1 μm) have also been assembled to form vertical arrays . Real‐time imaging of particles during the assembly process is possible for these larger particles, which are also closer to the dimensions used in top‐down device structures . For example, 2 μm diameter × 40–60 μm long Ni‐capped Si wires have been assembled using a magnetic field into sparse arrays in which individual particles are separated by several microns .…”

Section: Introductionmentioning

confidence: 99%

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Microwell‐Directed Self‐Assembly of Vertical Nanowire Arrays

Kirby

Smith

Keating

2013

Part & Part Syst Charact

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Vertical arrays of anisotropic particles are desired for many applications including solar cells, battery electrodes, and lasers. Partially etched nanowires (PENs) are hybrid silica nanotube/nanowires with partial metallic cores. These particles spontaneously form vertical arrays in which on average 70% of the particles are oriented perpendicular to the underlying substrate. Here, we perform PEN self‐assembly on lithographically prepared substrates patterned with square microwells having dimensions comparable to the length of the particles. Particle self‐assembly is observed both in the microwells and on the intervening surfaces. PENs both directly deposit into a well and diffuse across the surface between microwells until falling into a well. Assembly occurs as the local concentration of PENs in a well increases by these two mechanisms. Microwells provide a way to control array location on a surface and improve standing percentages up to 100% when the edge dimensions are decreased to a size approximately equal to the nanowire length. Microwells also protect against array disruption during sample drying.

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Fabrication of Oriented Polycrystalline MOF Superstructures

Linares‐Moreau,

Brandner,

Velásquez‐Hernández

et al. 2023

Advanced Materials

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The field of metal‐organic frameworks (MOFs) has progressed beyond the design and exploration of powdery and single‐crystalline materials. A current challenge is the fabrication of organized superstructures that can harness the directional properties of the individual constituent MOF crystals. To date, the progress in the fabrication methods of polycrystalline MOF superstructures has led to close‐packed structures with defined crystalline orientation. By controlling the crystalline orientation, the MOF pore channels of the constituent crystals can be aligned along specific directions: these systems possess anisotropic properties including enhanced diffusion along specific directions, preferential orientation of guest species, and protection of functional guests. In this perspective, we discuss the current status of MOF research in the fabrication of oriented polycrystalline superstructures focusing on the specific crystalline directions of orientation. Three methods are examined in detail: the assembly from colloidal MOF solutions, the use of external fields for the alignment of MOF particles, and the heteroepitaxial ceramic‐to‐MOF growth. This perspective aims at promoting the progress of this field of research and inspiring the development of new protocols for the preparation of MOF systems with oriented pore channels, to enable advanced MOF‐based devices with anisotropic properties.

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Magnetic Field Alignment of Randomly Oriented, High Aspect Ratio Silicon Microwires into Vertically Oriented Arrays

Cited by 17 publications

References 37 publications

Magnetic Control of MOF Crystal Orientation and Alignment

Magnetic Control of MOF Crystal Orientation and Alignment

Microwell‐Directed Self‐Assembly of Vertical Nanowire Arrays

Fabrication of Oriented Polycrystalline MOF Superstructures

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