Thu, 21 Aug 2008 09:43:03 BST CiteULike: kedmond's droplets http://www.citeulike.org/user/kedmond/tag/droplets CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/kedmond/article/2186364 <i>Science, Vol. 312, No. 5780. (16 June 2006), pp. 1631-1633.</i><br /><br />We present systematic and detailed measurements of interparticle contact forces inside three-dimensional piles of frictionless liquid droplets. We measured long-range chainlike correlations of the directions and magnitudes of large forces, thereby establishing the presence of force chains in three dimensions. Our correlation definition provides a chain persistence length of 10 mean droplet diameters, decreasing as load is applied to the pile. We also measured the angles between contacts and showed that the chainlike arrangement arises from the balance of forces. Moreover, we found that piles whose height was comparable to the chain persistence length exhibited substantially greater strain hardening than did tall piles, which we attributed to the force chains. Together, the results establish a connection between the microscopic force network and the elastic response of meso- or macroscopic granular piles. The conclusions drawn here should be relevant in jammed systems generally, including concentrated emulsions and piles of sand or other heavy particles. 10.1126/science.1125151 Measurement of Forces Inside a Three-Dimensional Pile of Frictionless Droplets J Zhou S Long Q Wang AD Dinsmore doi:10.1126/science.1125151 Science, Vol. 312, No. 5780. (16 June 2006), pp. 1631-1633. 2008-01-01T22:04:40-00:00 2006 Science 312 5780 1631 1633 droplets emulsions structure http://www.citeulike.org/user/kedmond/article/2007848 <i>Solid State Communications, Vol. 139, No. 11-12. (September 2006), pp. 557-561.</i><br /><br />I discuss how colloidal particles organize when they are confined by emulsion droplets. In these systems, the interplay between surface tension and interparticle repulsion drives the formation of complex, non-crystalline 3D arrangements. These can be classified into three groups: colloidosomes, or Pickering emulsions, structures that form when particles are bound to the interface of a spherical droplet; colloidal clusters, small polyhedral configurations of colloids formed by capillary forces generated in an evaporating emulsion droplet; and supraparticles, ball-shaped crystallites formed in the interior of emulsion droplets. I discuss the preparation, properties, and structure of each of these systems, using relevant results from geometry to describe how the particles organize. Colloidal spheres confined by liquid droplets: Geometry, physics, and physical chemistry Vinothan Manoharan doi:10.1016/j.ssc.2006.04.038 Solid State Communications, Vol. 139, No. 11-12. (September 2006), pp. 557-561. 2007-11-28T22:06:18-00:00 2006 Solid State Communications 139 11-12 557 561 clusters colloidal droplets self-assembly http://www.citeulike.org/user/kedmond/article/1219663 <i>Langmuir, Vol. 21, No. 6. (15 March 2005), pp. 2113-2116.</i><br /><br />Abstract: The controlled synthesis of nonspherical microparticles using microfluidics processing is described. Polymer droplets, formed by shearing a photopolymer using a continuous water phase at a T-junction, were constrained to adopt nonspherical shapes by confining them using appropriate microchannel geometries. Plugs were obtained by shearing the polymer phase at low shear rates, while disks were obtained by flattening droplets using a channel of low height. The nonspherical shapes formed were permanently preserved by photopolymerizing the constrained droplets in situ using ultraviolet light. Monodisperse plugs and disks of different lengths and diameters were obtained by varying the flow rates of the two phases. Controlled Synthesis of Nonspherical Microparticles Using Microfluidics D Dendukuri K Tsoi TA Hatton PS Doyle doi:10.1021/la047368k Langmuir, Vol. 21, No. 6. (15 March 2005), pp. 2113-2116. 2007-04-11T03:07:39-00:00 2005 Langmuir 21 6 2113 2116 colloidal droplets fluid fluorescence microscopy monodisperse http://www.citeulike.org/user/kedmond/article/1210848 <i>Science, Vol. 298, No. 5595. (1 November 2002), pp. 1006-1009.</i><br /><br />We present an approach to fabricate solid capsules with precise control of size, permeability, mechanical strength, and compatibility. The capsules are fabricated by the self-assembly of colloidal particles onto the interface of emulsion droplets. After the particles are locked together to form elastic shells, the emulsion droplets are transferred to a fresh continuous-phase fluid that is the same as that inside the droplets. The resultant structures, which we call "colloidosomes," are hollow, elastic shells whose permeability and elasticity can be precisely controlled. The generality and robustness of these structures and their potential for cellular immunoisolation are demonstrated by the use of a variety of solvents, particles, and contents. Colloidosomes: Selectively Permeable Capsules Composed of Colloidal Particles AD Dinsmore Ming Hsu MG Nikolaides Manuel Marquez AR Bausch DA Weitz doi:10.1126/science.1074868 Science, Vol. 298, No. 5595. (1 November 2002), pp. 1006-1009. 2007-04-05T12:51:02-00:00 2002 Science 298 5595 1006 1009 colloidal droplets emulsions microscopy monodisperse self-assembly http://www.citeulike.org/user/kedmond/article/1202376 <i>Applied Physics Letters, Vol. 82, No. 3. (2003), pp. 364-366.</i><br /><br />A flow-focusing geometry is integrated into a microfluidic device and used to study drop formation in liquid–liquid systems. A phase diagram illustrating the drop size as a function of flow rates and flow rate ratios of the two liquids includes one regime where drop size is comparable to orifice width and a second regime where drop size is dictated by the diameter of a thin "focused" thread, so drops much smaller than the orifice are formed. Both monodisperse and polydisperse emulsions can be produced. ©2003 American Institute of Physics. Formation of dispersions using “flow focusing” in microchannels Shelley Anna Nathalie Bontoux Howard Stone doi:10.1063/1.1537519 Applied Physics Letters, Vol. 82, No. 3. (2003), pp. 364-366. 2007-04-02T03:51:22-00:00 2003 Applied Physics Letters 82 3 364 366 AIP droplets emulsions fluid