Light-induced phase transitions of colloidal monolayers with crystalline order

Zaidouny, Lamiss; Bohlein, Thomas; Roth, Roland; Bechinger, Clemens

doi:10.1039/c3sm50945a

Cited by 26 publications

(23 citation statements)

References 28 publications

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“…Model systems composed of colloidal particles in periodic potentials have been studied for a number of years [28,29], from simple double well potentials [30][31][32][33] to directed motion [34][35][36][37][38][39], particle sorting [40], and kink generation [41] in two-dimensional (2D) optical lattices. Colloidal systems are easy to manipulate, and have accessible length and time scales, making them attractive models for the study of synchronisation at the microscale.…”

Section: Introductionmentioning

confidence: 99%

Dynamic mode locking in a driven colloidal system: experiments and theory

et al. 2017

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In this article we examine the dynamics of a colloidal particle driven by a modulated force over a sinusoidal optical potential energy landscape. Coupling between the competing frequencies of the modulated drive and that of particle motion over the periodic landscape leads to synchronisation of particle motion into discrete modes. This synchronisation manifests as steps in the average particle velocity, with mode locked steps covering a range of average driving velocities. The amplitude and frequency dependence of the steps are considered, and compared to results from analytic theory, Langevin dynamics simulations, and dynamic density functional theory. Furthermore, the critical driving velocity is studied, and simulation used to extend the range of conditions accessible in experiments alone. Finally, state diagrams from experiment, simulation, and theory are used to show the extent of the dynamically locked modes in two dimensions, as a function of both the amplitude and frequency of the modulated drive.

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Section: Introductionmentioning

confidence: 99%

Dynamic mode locking in a driven colloidal system: experiments and theory

et al. 2017

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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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“…The potential maxima are indicated by the darker shadings, so the vortices are attracted to the light colored regions. This type of system has been studied previously for colloids interacting with q1D periodic substrate arrays, where it was shown that various melting and structural transitions between hexagonal, smectic, and disordered colloidal arrangements can occur [46][47][48][49][50][51][52] . In general, the colloidal studies focused on the case where the particle lattice constant a is larger than the substrate lattice constant w. Martinoli et al investigated vortex pinning in samples with a 1D periodic thickness modulation [53][54][55] and observed broad commensuration peaks in the depinning threshold that were argued to be correlated with the formation of ordered vortex arrangements that could align with the substrate periodicity.…”

Section: Introductionmentioning

confidence: 99%

Orientational ordering, buckling, and dynamic transitions for vortices interacting with a periodic quasi-one-dimensional substrate

2016

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We examine the statics and dynamics of vortices in the presence of a periodic quasi-one dimensional substrate, focusing on the limit where the vortex lattice constant is smaller than the substrate lattice period. As a function of the substrate strength and filling factor, within the pinned state we observe a series of order-disorder transitions associated with buckling phenomena in which the number of vortex rows that fit between neighboring substrate maxima increases. These transitions coincide with steps in the depinning threshold, jumps in the density of topological defects, and changes in the structure factor. At the buckling transition the vortices are disordered, while between the buckling transitions the vortices form a variety of crystalline and partially ordered states. In the weak substrate limit, the buckling transitions are absent and the vortices form an ordered hexagonal lattice that undergoes changes in its orientation with respect to the substrate as a function of vortex density. At intermediate substrate strength, certain ordered states appear that are correlated with peaks in the depinning force. Under an applied drive the system exhibits a rich variety of distinct dynamical phases, including plastic flow, a density-modulated moving crystal, and moving floating solid phases. We also find a dynamic smectic-to-smectic transition in which the smectic ordering changes from being aligned with the substrate to being aligned with the external drive. The different dynamical phases can be characterized using velocity histograms and the structure factor. We discuss how these results are related to recent experiments on vortex ordering in thin films with periodic thickness modulations. Our results should also be relevant for other types of systems such as ions, colloids, or Wigner crystals interacting with periodic quasi-one-dimensional substrates.

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Light-induced phase transitions of colloidal monolayers with crystalline order

Cited by 26 publications

References 28 publications

Dynamic mode locking in a driven colloidal system: experiments and theory

Dynamic mode locking in a driven colloidal system: experiments and theory

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

Orientational ordering, buckling, and dynamic transitions for vortices interacting with a periodic quasi-one-dimensional substrate

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