Phases of Thin Colloidal Layers

MRS Bulletin ◽  
1998 ◽  
Vol 23 (10) ◽  
pp. 33-38 ◽  
Author(s):  
Cherry Murray
Keyword(s):  
Self Assembly ◽  
Optical Materials ◽  
Colloidal Particles ◽  
Three Dimensional ◽  
Colloidal Suspensions ◽  
Dielectric Behavior ◽  
Thin Layers ◽  
Photonic Bandgap Materials ◽  
Colloidal Spheres ◽  
Assembly Technique

Colloids have long been used in applications such as paints, coatings, foods, and many manufacturing processes. Recently, synthetic crystalline arrays of colloidal particles have been used as novel optical materials such as diffractive filters, mimicking the optical properties of opals—natural colloidal crystals made from silica spheres. Colloidal assembly has been proposed to manufacture photonic bandgap materials that can be tailored and that could have many uses in optical devices. The advantages of using colloids to do the self-assembly of novel materials are the relative ease with which monodisperse spheres comparable in size to the wavelength of light can be manufactured and also the demonstrated ease by which some suspensions of monodisperse colloidal spheres crystallize when placed under favorable conditions. Before we can use colloidal crystallization as a controlled self-assembly technique for making novel optical materials, we need (1) to create a means of manufacturing large quantities of monodisperse particles of the desired dielectric behavior, (2) to understand the phase diagram and nucleation phenomena of colloidal suspensions, and (3) to find an easy means to fix the particles in place once they selforganize. In this article, I focus on the second point just mentioned, I give an overview of the phases and some of the complex phenomena encountered in three-dimensional (3D) suspensions and in thin layers of monodisperse colloidal spheres between smooth walls, and I then briefly mention the greater complexity encountered in bidisperse systems. The first and third points will be dealt with elsewhere in this issue.

In Situ Visualization of Layer Transitions during Convective Self-Assembly in a Sessile Drop

2007 ◽  
Vol 31 ◽  
pp. 117-119
Author(s):  
Li Gao ◽  
Qing Feng Yan ◽  
C.C. Wong ◽  
Yet Ming Chiang
Keyword(s):  
Self Assembly ◽  
Sessile Drop ◽  
Three Dimensional ◽  
Colloidal Crystals ◽  
Layer Transition ◽  
Simple Method ◽  
Colloidal Spheres ◽  
In Situ Visualization ◽  
Set Up

Convective self-assembly of colloidal spheres provides a simple method for fabricating two and three dimensional colloidal crystals. In this work, we investigated the layer transitions phenomena during colloidal self-assembly in a sessile drop by using an in-situ videoscopic set-up. The effects of surface charge, colloidal concentration, and surfactant additions were examined. The results show that the chemical environment plays an important role in colloidal self-assembly. In the case of ordered growth, different layer transition phenomena were observed when the colloidal concentration is different.

Dielectrophoretic Mixing With Novel Electrode Geometry

2009 ◽  
Author(s):  
G. Naga Siva Kumar ◽  
Sushanta K. Mitra ◽  
Subir Bhattacharjee
Keyword(s):  
Electric Field ◽  
Cell Activation ◽  
Colloidal Particles ◽  
Colloidal Suspension ◽  
Three Dimensional ◽  
Colloidal Suspensions ◽  
Navier Stokes ◽  
Mixing Efficiency ◽  
Computational Domain ◽  
Element Analysis

Electrokinetic mixing of analytes at micro-scale is important in several biochemical applications like cell activation, DNA hybridization, protein folding, immunoassays and enzyme reactions. This paper deals with the modeling and numerical simulation of micromixing of two different types of colloidal suspensions based on principle of dielectrophoresis (DEP). A mathematical model is developed based on Laplace, Navier-Stokes, and convection-diffusion-migration equations to calculate electric field, velocity, and concentration distributions, respectively. Mixing of two colloidal suspensions is simulated in a three-dimensional computational domain using finite element analysis considering dielectrophoretic, gravitational and convective (advective)–diffusive forces. Phase shifted AC signal is applied to the alternating electrodes for achieving the mixing of two different colloidal suspensions. The results indicate that the electric field and DEP forces are maximum at the edges of the electrodes and become minimum elsewhere. As compared to curved edges, straight edges of electrodes have lower electric field and DEP forces. The results also indicate that DEP force decays exponentially along the height of the channel. The effect of DEP forces on the concentration profile is studied. It is observed that, the concentration of colloidal particles at the electrodes edges is very less compared to elsewhere. Mixing of two colloidal suspensions due to diffusion is observed at the interface of the two suspensions. The improvement in mixing after applying the repulsive DEP forces on the colloidal suspension is observed. Most of the mixing takes place across the slant edges of the triangular electrodes. The effect of electrode pairs and the mixing length on degree of mixing efficiency are also observed.

scholarly journals Control of colloidal placement by modulated molecular orientation in nematic cells

2016 ◽  
Vol 2 (9) ◽  
pp. e1600932 ◽  
Author(s):  
Chenhui Peng ◽  
Taras Turiv ◽  
Yubing Guo ◽  
Sergij V. Shiyanovskii ◽  
Qi-Huo Wei ◽  
...  
Keyword(s):  
Self Assembly ◽  
Molecular Orientation ◽  
Colloidal Particles ◽  
Orientational Order ◽  
Thermal Fluctuations ◽  
Single Type ◽  
Surface Anchoring ◽  
Colloidal Spheres ◽  
Elastic Forces ◽  
Spatially Varying

Colloids self-assemble into various organized superstructures determined by particle interactions. There is tremendous progress in both the scientific understanding and the applications of self-assemblies of single-type identical particles. Forming superstructures in which the colloidal particles occupy predesigned sites and remain in these sites despite thermal fluctuations represents a major challenge of the current state of the art. We propose a versatile approach to directing placement of colloids using nematic liquid crystals with spatially varying molecular orientation preimposed by substrate photoalignment. Colloidal particles in a nematic environment are subject to the long-range elastic forces originating in the orientational order of the nematic. Gradients of the orientational order create an elastic energy landscape that drives the colloids into locations with preferred type of deformations. As an example, we demonstrate that colloidal spheres with perpendicular surface anchoring are driven into the regions of maximum splay, whereas spheres with tangential surface anchoring settle into the regions of bend. Elastic forces responsible for preferential placement are measured by exploring overdamped dynamics of the colloids. Control of colloidal self-assembly through patterned molecular orientation opens new opportunities for designing materials and devices in which particles should be placed in predesigned locations.

Preparation and Properties of Silica Inverse Opal via Self-Assembly

2014 ◽  
Vol 699 ◽  
pp. 318-324 ◽  
Author(s):  
Syara Kassim ◽  
S. Padmanabhan ◽  
J. McGrath ◽  
M.E. Pemble
Keyword(s):  
Photonic Crystals ◽  
Self Assembly ◽  
Colloidal Particles ◽  
Photonic Band Gap ◽  
Three Dimensional ◽  
Colloidal Synthesis ◽  
3 Dimensional ◽  
Inverse Opals ◽  
Simple Processing ◽  
Potential Applications

The bottom-up colloidal synthesis of photonic band gap (PBG) materials or photonic crystals (PC) has attracted considerable interest as compared to so-called top-down lithographic approaches due to the simple processing steps involved and the prospect of the economically viable production of complex 3-dimensional optical materials from simple colloidal particles. To date self-assembly techniques constitute the most popular approach to fabricate 3D photonic crystals from colloidal particle suspensions. Based on the natural tendency of monodisperse colloidal particles to organise into ordered arrays, this method represent the best option due to the ease of fabrication, ability to produce larger area samples and cost. Here we report on the fabrication of long range three-dimensional (3D) ordered poly (methyl methacrylate) (PMMA)-silica PC structures and the subsequent fabrication of robust silica inverse opals using self-assembly methods. The optical properties of these materials are described and discussed in terms of potential applications of these materials.

scholarly journals Self-Assembly of Polyhedral Hybrid Colloidal Particles

2008 ◽  
Vol 1135 ◽  
Author(s):  
Adeline Perro ◽  
Etienne Duguet ◽  
Serge Ravaine ◽  
Vinothan N. Manoharan
Keyword(s):  
Self Assembly ◽  
Colloidal Particles ◽  
Dimensional Space ◽  
Three Dimensional ◽  
High Yield ◽  
Complex Geometries ◽  
Hybrid Particles ◽  
Line Segments ◽  
Very High ◽  
Three Dimensional Space

ABSTRACTWe have developed a new method to produce hybrid particles with polyhedral shapes in very high yield (liter quantities at up to 70% purity) using a combination of emulsion polymerization and inorganic surface chemistry. The procedure has been generalized to create complex geometries, including hybrid line segments, triangles, tetrahedra, octahedra, and more. The optical properties of these particles are tailored for studying their dynamics and self-assembly. For example, we produce systems that consist of index-matched spheres allowing us to define the position of each elementary particle in three-dimensional space. We present some preliminary studies on the self-assembly of these complex shaped systems based on electron and optical microscopy.

scholarly journals Plasmonic Nanoparticles Driven Enhanced Light Amplification in a Local 2D and 3D Self-Assembly

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1051 ◽  
Author(s):  
Konrad Cyprych ◽  
Denis Chateau ◽  
Anthony Désert ◽  
Stephane Parola ◽  
Jaroslaw Mysliwiec
Keyword(s):  
Self Assembly ◽  
Three Dimensional ◽  
Thin Layers ◽  
Enhancement Effect ◽  
Two Dimensional ◽  
Random Lasing ◽  
Light Amplification ◽  
Multilamellar Liposomes ◽  
Solid Thin Films ◽  
2D And 3D

We present fluorescence and a random lasing enhancement effect due to the interaction between gold nanoparticles (AuNPs) and Rhodamine 6G (Rh6G) dye. Non-covalently bounded dyes in the proximity of nanoparticles are studied in three systems of varying dimensionality: from (i) three-dimensional freely distributed suspensions, through (ii) quasi-two-dimensional multilamellar liposomes, to (iii) solid two-dimensional thin layers. Liposomes facilitate the formation of stable AuNPs/Rh6G composition showing enhanced fluorescence, while solid thin films exhibit plasmon-assisted random lasing.

Interactions and Dynamics in Charge-Stabilized Colloids

MRS Bulletin ◽  
1998 ◽  
Vol 23 (10) ◽  
pp. 24-31 ◽  
Author(s):  
John C. Crocker ◽  
David G. Grier
Keyword(s):  
Self Assembly ◽  
Colloidal Particles ◽  
Protein Crystallization ◽  
Colloidal Suspensions ◽  
Industrial Processes ◽  
Fluid Medium ◽  
Nano Structures ◽  
Naturally Occurring ◽  
Electrostatic Stabilization ◽  
Natural Tendency

Perhaps the most remarkable observation one can make about colloidal suspensions is that they exist at all. Particles dispersed in a fluid medium have a natural tendency to aggregate under the influence of van der Waals attraction. Yet the fortunes of a great many natural and industrial processes require colloidal particles to remain dispersed or at least to aggregate at a controlled rate. The existence of colloidal suspensions as varied as milk, inks, and metallic sols attests to the efficacy of a variety of stabilizing mechanisms. As early as 1809, Russel realized that many naturally occurring colloidal particles are charged. By the end of the century, Schultz and Hardy demonstrated that the resulting electro-static repulsions were strong enough to stabilize their suspensions against flocculating. This mechanism—arguably the best understood—continues to yield new surprises despite more than a century of analysis. The most recent burst of activity has been driven by the development of new and quite general techniques for measuring colloidal and macromolecular interactions. Its counterintuitive result—that like-charged particles some-times attract each other—may have ramifications in areas as diverse as protein crystallization, self-assembly of nano-structures, and the stabilization of industrial suspensions. This article touches briefly on the well-established theory of electrostatic stabilization in colloidal suspensions. The emphasis here is on the approximations that have provided the community with an analytical theory at the expense of overlooking recently discovered effects.

Novel three-dimensional autologous tissue-engineered vaginal tissues using the self-assembly technique

2017 ◽  
Vol 180 ◽  
pp. 22-36 ◽  
Author(s):  
Hazem Orabi ◽  
Ingrid Saba ◽  
Alexandre Rousseau ◽  
Stéphane Bolduc
Keyword(s):  
Self Assembly ◽  
Three Dimensional ◽  
The Self ◽  
Autologous Tissue ◽  
Assembly Technique

Three-Dimensional Integration Technology Based on Self-Assembled Chip-to-Wafer Stacking

2008 ◽  
Vol 1112 ◽  
Author(s):  
Takafumi Fukushima ◽  
Tetsu Tanaka ◽  
Mitsumasa Koyanagi
Keyword(s):  
Self Assembly ◽  
Three Dimensional ◽  
The Self ◽  
High Yield ◽  
3D Integration ◽  
Integration Technology ◽  
Pick And Place ◽  
Assembly Technique ◽  
Self Assembled ◽  
Short Time

AbstractWe have demonstrated that a number of known good dies (KGDs) can be precisely aligned in batch and stacked on LSI wafers by our chip-to-wafer three-dimensional (3D) integration technology using an innovative self-assembly technique. Compared with conventional robotic pick-and-place chip assembly, the fluidic self-assembly can provide high-throughput chip alignment and bonding, and the resulting self-assembled chips have high alignment accuracy of approximately 0.3 micron on average. Immediately after chip release, the chips are aligned onto the predetermined hydrophilic bonding areas in a short time within 0.1 sec by the surface tension of aqueous liquid used in our self-assembly. By using the self-assembly, a number of KGDs with different chip sizes, different materials and different devices can be stacked in high yield to give highly integrated 3D chips we call the 3D Super Chip.

Sign in / Sign up

Export Citation Format

Share Document