Sat, 26 Jul 2008 06:10:37 BST CiteULike: dchen's Kim http://www.citeulike.org/user/dchen/author/Kim CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/2910642 <i>Soft Matter, 2008, 4, 1151 - 1157, DOI: 10.1039/b714376a</i><br /><br />Stimuli-responsive polymer gels have received considerable attention due to their singular mechanical properties, which make them materials of choice for niche applications. Polymer gels comprising either physical or chemical cross-links can undergo controlled and reversible shape changes in response to an applied field. The stimulus or external field applied may include thermal, electrical, magnetic, pH, UV/visible light, ionic or metallic interactions or combinations thereof. The shape change can manifest itself in two-dimensional actuation, bending motion, or three-dimensional actuation, volume change. This reversible contraction and expansion of polymer gels as well as their mechanical properties are similar to that of biological muscles. This review will describe and critique some of the recent advances in the field of stimuli-responsive polymer gels including the design of new classes of polymeric gels, controlled actuation in response to external stimuli, and ability to tailor material properties for different applications. Stimuli-responsive polymer gels Suk-Kyun Ahn Rajeswari Kasi Seong-Cheol Kim Nitin Sharma Yuxiang Zhou Soft Matter, 2008, 4, 1151 - 1157, DOI: 10.1039/b714376a 2008-06-20T14:55:03-00:00 Soft Matter, 2008, 4, 1151 - 1157, DOI: 10.1039/b714376a 2008 gel polymer review http://www.citeulike.org/user/dchen/article/2754251 <i>Physical Review Letters, Vol. 98, No. 18. (2007)</i><br /><br />Magnetic transmission x-ray microscopy is used to directly visualize the influence of a spin-polarized current on domain walls in curved permalloy wires. Pulses of nanosecond duration and of high current density up to 1.0×1012 A/m2 are used to move and to deform the domain wall. The current pulse drives the wall either undisturbed, i.e., as composite particle through the wire, or causes structural changes of the magnetization. Repetitive pulse measurements reveal the stochastic nature of current-induced domain-wall motion. Direct Imaging of Stochastic Domain-Wall Motion Driven by Nanosecond Current Pulses Guido Meier Markus Bolte René Eiselt Benjamin Krüger Dong Kim Peter Fischer doi:10.1103/PhysRevLett.98.187202 Physical Review Letters, Vol. 98, No. 18. (2007) 2008-05-04T16:33:53-00:00 2007 Physical Review Letters 98 18 APS 2007 focus magnetic material http://www.citeulike.org/user/dchen/article/2709644 <i>Langmuir, Vol. 22, No. 14. (4 July 2006), pp. 6024-6030.</i><br /><br />Abstract: Spray drying of complex liquids to form solid powders is important in many industrial applications. One of the challenges associated with spray drying is controlling the morphologies of the powders produced; this requires an understanding of how drying mechanics depend on the ingredients and conditions. We demonstrate that the morphology of powders produced by spray drying colloidal polystyrene (PS) suspensions can be significantly altered by changing the molecular weight of dissolved poly(ethylene oxide) (PEO). Samples containing high-molecular-weight PEO produce powders with more crumpled morphologies than those containing low-molecular-weight PEO. Observations of drying droplets suspended by a thin film of vapor suggest that this occurs because the samples with high-molecular-weight PEO buckle earlier in the drying process when the droplets are larger. Earlier buckling times are likely caused by the decreased stability, demonstrated by bulk rheology experiments, of PS particles in the presence of high-molecular-weight PEO at elevated temperatures. We present a consistent picture in which decreased particle stability hastens droplet buckling and leads to more crumpled powder morphologies; this underscores the importance of interparticle forces in determining the buckling of particle-laden droplets. Buckling and Crumpling of Drying Droplets of Colloid-Polymer Suspensions Y Sugiyama RJ Larsen JW Kim DA Weitz doi:10.1021/la053419h Langmuir, Vol. 22, No. 14. (4 July 2006), pp. 6024-6030. 2008-04-23T17:51:21-00:00 2006 Langmuir 22 14 6024 6030 colloids drying weitz http://www.citeulike.org/user/dchen/article/2709589 <i>J. Am. Chem. Soc., Vol. 128, No. 44. (8 November 2006), pp. 14374-14377.</i><br /><br />Abstract: We describe a promising and flexible technique for fabricating uniform nonspherical particles with anisotropic phase and surface properties. Our approach is based on the seeded polymerization technique in which monomer-swollen particles are polymerized. The polymerization causes a phase separation to occur, giving rise to two-phase nonspherical particles. We show that the elastic contraction of the swollen polymer particles induced by elevated polymerization temperatures plays an important role in the phase separation. Moreover, chemical anisotropy of nonspherical particles can be obtained by using immiscible polymer pairs and by employing surface treatments. Furthermore, we are able to produce amphiphilic dumbbell particles consisting of two different bulbs: hydrophilic poly (ethylene imine)-coated polystyrene and hydrophobic polystyrene. Controlled geometries of these amphiphilic nonspherical particles will allow a wide range of potential applications, such as engineered colloid surfactants. Synthesis of Nonspherical Colloidal Particles with Anisotropic Properties JW Kim RJ Larsen DA Weitz doi:10.1021/ja065032m J. Am. Chem. Soc., Vol. 128, No. 44. (8 November 2006), pp. 14374-14377. 2008-04-23T17:26:53-00:00 2006 J. Am. Chem. Soc. 128 44 14374 14377 2006 colloids weitz http://www.citeulike.org/user/dchen/article/2683459 <i>Advanced Materials, Vol. 19, No. 15. (2007), pp. 2005-2009.</i><br /><br />No abstract. Uniform Nonspherical Colloidal Particles with Tunable Shapes JW Kim R J Larsen D A Weitz doi:10.1002/adma.200602345 Advanced Materials, Vol. 19, No. 15. (2007), pp. 2005-2009. 2008-04-17T20:35:27-00:00 2007 Advanced Materials 19 15 2005 2009 2007 colloids technique weitz http://www.citeulike.org/user/dchen/article/2683388 <i>Nano Lett., Vol. 7, No. 9. (12 September 2007), pp. 2876-2880.</i><br /><br />Abstract: We present a robust and straightforward approach for fabricating a novel colloidosome system where colloidal particles are assembled to form colloidal shells on the surface of stimuli-responsive microgel scaffolds. We demonstrate that the structural properties of the colloidal shells can be controlled through the colloidal particle size and modulus, and the state of supporting microgel particles. This technique offers a new way to engineer colloidosomes, enabling fine control over their permeability over a wide range of length scales. Colloidal Assembly Route for Responsive Colloidosomes with Tunable Permeability JW Kim A Fernandez-Nieves N Dan AS Utada M Marquez DA Weitz doi:10.1021/nl0715948 Nano Lett., Vol. 7, No. 9. (12 September 2007), pp. 2876-2880. 2008-04-17T20:10:58-00:00 2007 Nano Lett. 7 9 2876 2880 2007 colloid emulsion weitz http://www.citeulike.org/user/dchen/article/2683315 <i>Applied Physics Letters, Vol. 91, No. 13. (2007)</i><br /><br />View this record in Web of Science Controlled production of emulsion drops using an electric field in a flow-focusing microfluidic device Haejune Kim Dawei Luo Darren Link David Weitz Manuel Marquez Zhengdong Cheng Applied Physics Letters, Vol. 91, No. 13. (2007) 2008-04-17T19:47:51-00:00 2007 Applied Physics Letters 91 13 AIP emulsion flow weitz http://www.citeulike.org/user/dchen/article/2683180 <i>Angewandte Chemie International Edition, Vol. 46, No. 47. (2007), pp. 8970-8974.</i><br /><br />No Abstract Controllable Monodisperse Multiple Emulsions Liang-Yin Chu Andrew s Rhutesh k Jin-Woong Kim David a doi:10.1002/anie.200701358 Angewandte Chemie International Edition, Vol. 46, No. 47. (2007), pp. 8970-8974. 2008-04-17T18:59:41-00:00 2007 Angewandte Chemie International Edition 46 47 8970 8974 2008 emulsion people weitz http://www.citeulike.org/user/dchen/article/2553079 <i>Physical Review Letters, Vol. 99, No. 2. (2007)</i><br /><br />Colloidal suspensions are susceptible to gravitationally induced phase separation. This can be mitigated by the formation of a particle network caused by depletion attraction. The effectiveness of this network in supporting the buoyant weight of the suspension can be characterized by its compressional modulus. We measure the compressional modulus for emulsion networks induced by depletion attraction and present a model that quantitatively predicts their gravitational stability. We also determine the relationship between the strength of the depletion attraction and the magnitude of the compressional modulus. Gravitational Stability of Suspensions of Attractive Colloidal Particles Chanjoong Kim Yaqian Liu Angelika Kühnle Stephan Hess Sonja Viereck Thomas Danner L Mahadevan David Weitz doi:10.1103/PhysRevLett.99.028303 Physical Review Letters, Vol. 99, No. 2. (2007) 2008-03-18T22:07:07-00:00 2007 Physical Review Letters 99 2 APS 2007 colloids gel weitz http://www.citeulike.org/user/dchen/article/2552521 <i>Physical Review Letters, Vol. 99, No. 18. (2007)</i><br /><br />Experiments show that bubbles covered with monodisperse polystyrene particles, with particle to bubble radius ratios of about 0.1, evolve to form faceted polyhedral shapes that are stable to dissolution in air-saturated water. We perform Surface Evolver simulations and find that the faceted particle-covered bubble represents a local minimum of energy. At the faceted state, the Laplace overpressure vanishes, which together with the positive slope of the bubble pressure-volume curve, ensures phase stability. The repulsive interactions between the particles cause a reduction of the curvature of the gas-liquid interface, which is the mechanism that arrests dissolution and stabilizes the bubbles. Dissolution Arrest and Stability of Particle-Covered Bubbles Manouk Abkarian Anand Subramaniam Shin Kim Ryan Larsen Seung Yang Howard Stone doi:10.1103/PhysRevLett.99.188301 Physical Review Letters, Vol. 99, No. 18. (2007) 2008-03-18T19:09:16-00:00 2007 Physical Review Letters 99 18 APS 2007 colloids