Phase behavior of colloidal monolayers in quasiperiodic light fields

Mikhael, Jules; Gera, Günter; Bohlein, Thomas; Bechinger, Clemens

doi:10.1039/c0sm00486c

Cited by 30 publications

(25 citation statements)

References 28 publications

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“…Under micro-gravity conditions hard sphere crystal nucleation and growth was templated on seed crystals placed in the bulk of the host suspension [22]. In addition to topological templates exploiting excluded volume interactions, also light grids exploiting photophoresis were used to fabricate individual 2D crystals and quasi-crystals [23,24]. Use of holographic tweezer trapped seed structures allowed precise localization and orientation in 3D [25].…”

Section: Introductionmentioning

confidence: 99%

Controlled assembly of single colloidal crystals using electro-osmotic micro-pumps

Niu

Oğuz

Müller

et al. 2017

Phys. Chem. Chem. Phys.

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Abstract:We assemble charged colloidal spheres at deliberately chosen locations on a charged unstructured glass substrate utilizing ion exchange based electro-osmotic micro-pumps.Using microscopy, a simple scaling theory and Brownian Dynamics simulations, we systematically explore the control parameters of crystal assembly and the mechanisms through which they depend on the experimental boundary conditions. We demonstrate that crystal quality depends crucially on the assembly distance of the colloids. This is understood as resulting from the competition between inward transport by the electro-osmotic pump flow and the electro-phoretic outward motion of the colloids. Optimized conditions include substrates of low and colloids of large electro-kinetic mobility. Then a sorting of colloids by size is observed in binary mixtures with larger particles assembling closer to the ion exchanger beads. Moreover, mono-sized colloids form defect free single domain crystals which grow outside a colloid-free void with facetted inner crystal boundaries centred on the ion exchange particle. This works remarkably well, even with irregularly formed ion exchange resin splinters.

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Section: Introductionmentioning

confidence: 99%

Controlled assembly of single colloidal crystals using electro-osmotic micro-pumps

Niu

Oğuz

Müller

et al. 2017

Phys. Chem. Chem. Phys.

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“…Bond-lengths were calculated based on a Delaunay triangulation 27,28 that identies the bonds between each particle and its nearest neighbour. Fig.…”

Section: Resultsmentioning

confidence: 99%

Light-induced phase transitions of colloidal monolayers with crystalline order

et al. 2013

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We experimentally study the phase behavior of a charge-stabilized two-dimensional colloidal crystal which is subjected to a one-dimensional periodic light field. Such light fields are created by a scanned optical line tweezer which allows the variation of the periodicity without optical realignments. In order to realize a wide range of line spacings relative to the lattice constant, we use a suspension of silica particles in bromobenzene. This colloidal system has a Debye screening length of about 4.6 mm which results in the formation of crystals with lattice constants up to 20 mm. Because the refractive index of bromobenzene is larger than that of the colloids, optical gradient forces lead to the attraction of particles at regions where the intensity is smallest. Depending on the depth and periodicity of the optical potential, we observe the light-induced assembly of colloids into triangular, rhombic and square phases.

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confidence: 94%

“…Tilings with fivefold (18, 19), sevenfold (20), eightfold (21), ninefold (22), tenfold (23), twelvefold (24), and other (25) quasicrystalline symmetries were realized, demonstrating analogous ordering mechanisms as in quasicrystals (26,27). These ordering mechanisms and the formation dynamics were particularly explored in quasicrystalline colloidal monolayers stabilized by interfering laser beams (28,29).Nematic liquid crystals are fluids with molecular orientational order, called the director field, and it is by designing the profiles of this field that colloidal structures of various functionalities can be self-assembled. The self-assembly is based on effective structural forces emerging between the particles (typically ∼1−10 pN for micrometer-sized particles), caused by the inhomogeneous and anisotropic director profiles imposed by the particle surfaces or general shapes (30).…”

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confidence: 95%

Quasicrystalline tilings with nematic colloidal platelets

Dontabhaktuni

Ravnik

Žumer

2014

Proc. Natl. Acad. Sci. U.S.A.

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Complex nematic fluids have the remarkable capability for selfassembling regular colloidal structures of various symmetries and dimensionality according to their micromolecular orientational order. Colloidal chains, clusters, and crystals were demonstrated recently, exhibiting soft-matter functionalities of robust binding, spontaneous chiral symmetry breaking, entanglement, shapedriven and topological driven assembly, and even memory imprinting. However, no quasicrystalline structures were found. Here, we show with numerical modeling that quasicrystalline colloidal lattices can be achieved in the form of original Penrose P1 tiling by using pentagonal colloidal platelets in layers of nematic liquid crystals. The tilings are energetically stabilized with binding energies up to 2500 k B T for micrometer-sized platelets and further allow for hierarchical substitution tiling, i.e., hierarchical pentagulation. Quasicrystalline structures are constructed bottom-up by assembling the boat, rhombus, and star maximum density clusters, thus avoiding other (nonquasicrystalline) stable or metastable configurations of platelets. Central to our design of the quasicrystalline tilings is the symmetry breaking imposed by the platelet shape and the surface anchoring conditions at the colloidal platelets, which are misaligning and asymmetric over two perpendicular mirror planes. Finally, the design of the quasicrystalline tilings as platelets in nematic liquid crystals is inherently capable of a continuous variety of length scales of the tiling, ranging over three orders of magnitude in the typical length (from ∼ 10 nm to ∼ 10 μm), which could allow for the design of quasicrystalline photonics at multiple frequency ranges.colloids | quasicrystals | Penrose tiling | hierarchy Q uasicrystals are aperiodic crystalline materials, distinguished by noncrystallographic rotational symmetry of fivefold, sevenfold, eightfold, and higher rotational symmetry axes (1-3). These symmetries are typically found in atomic lattices of distinct metallic alloys (1, 4). However, more recently, a unique class of soft-matter quasicrystals is emerging (5-8), where the basic building blocks are not single atoms but rather macromolecules (9, 10), copolymers (11), molecular liquid crystalline fields (12, 13), or colloidal particles (14, 15). Two-dimensional realizations of materials with quasicrystalline symmetries are quasicrystalline tilings (2,16,17). In tilings, the structures of polygons or platelets-tiles-cover an area in complex patterns, typically following geometric rules. Tilings with fivefold (18, 19), sevenfold (20), eightfold (21), ninefold (22), tenfold (23), twelvefold (24), and other (25) quasicrystalline symmetries were realized, demonstrating analogous ordering mechanisms as in quasicrystals (26,27). These ordering mechanisms and the formation dynamics were particularly explored in quasicrystalline colloidal monolayers stabilized by interfering laser beams (28,29).Nematic liquid crystals are fluids with molecular orientational order, called t...

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Phase behavior of colloidal monolayers in quasiperiodic light fields

Cited by 30 publications

References 28 publications

Controlled assembly of single colloidal crystals using electro-osmotic micro-pumps

Controlled assembly of single colloidal crystals using electro-osmotic micro-pumps

Light-induced phase transitions of colloidal monolayers with crystalline order

Quasicrystalline tilings with nematic colloidal platelets

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