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Contact Line (contact + line)
Selected AbstractsDirected Self-Assembly of Gradient Concentric Carbon Nanotube Rings,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2008Suck Won Hong Abstract Hundreds of gradient concentric rings of linear conjugated polymer, (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4- phenylenevinylene], i.e., MEH-PPV) with remarkable regularity over large areas were produced by controlled "stick-slip" motions of the contact line in a confined geometry consisting of a sphere on a flat substrate (i.e., sphere-on-flat geometry). Subsequently, MEH-PPV rings were exploited as a template to direct the formation of gradient concentric rings of multiwalled carbon nanotubes (MWNTs) with controlled density. This method is simple, cost effective, and robust, combining two consecutive self-assembly processes, namely, evaporation-induced self-assembly of polymers in a sphere-on-flat geometry, followed by subsequent directed self-assembly of MWNTs on the polymer-templated surfaces. [source] Height functions for applying contact angles to 3D VOF simulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2009S. Afkhami Abstract A rigorous methodology is presented for applying a contact angle as a contact line boundary condition within a 3D volume-of-fluid-based flow algorithm, based on the recently developed height function methodology that yields accurate interface normals and curvatures from volume fractions. We demonstrate that the approach yields accurate estimates of curvature and surface tension at a contact line, values that converge with spatial refinement. We then study the efficacy of this approach via examples of both static and dynamic contact line phenomena. Copyright © 2008 John Wiley & Sons, Ltd. [source] Top-down processed silicon nanowire transistor arrays for biosensingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2009Xuan Thang Vu Abstract We describe the fabrication, electrical and electrochemical characterization of silicon nanowire arrays, which were processed in a top-down approach using combined nanoimprint lithography and wet chemical etching. We used the top silicon layer as contact line and observed an influence of implantation and subsequent annealing of these lines to the device performance. In addition we found a subthreshold slope dependence on wire size. When operated in a liquid environment, wires can be utilized as pH sensors. We characterized the pH sensitivity in the linear range and in the subthreshold operation regime. As a first proof-of-principle experiment for the later use of the sensors in bioassays, we monitored the buildup of polyelectrolyte multilayers on the wire surface. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Meniscus deformation and dynamics of moving contact line between poly(ethylene terephthalate) surface and glycerol,water mixturesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009Dr Stoyan I. Karakashev Abstract The microscopic hydrodynamic (HD) and macroscopic theories for describing the meniscus deformation and dynamics of a moving contact line have been analyzed and compared by using the extrapolated dynamic contact angles between a poly(ethylene terephthalate) (PET) surface and glycerol,water mixtures. The analysis showed that the microscopic theory is confined by the microscopic length scale and small capillary number. The macroscopic theory is not subjected to any restrictions. Three (inner, intermediate and outer) regions of the dynamic meniscus have been combined by using the contact molecular kinetics and hydrodynamics. The combined molecular-HD theory has been validated using the experimental data for the extrapolated dynamic contact angles between a PET surface and glycerol,water mixtures. The analysis showed that the combined theory describes the phenomenon of wetting qualitatively. It was found that the contradiction within the theoretical framework of the molecular kinetics and hydrodynamics hinders the exact description of the wetting phenomenon. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Enhancing drop stability in protein crystallization by chemical patterningACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2005Viatcheslav Berejnov The motion of protein drops on crystallization media during routine handling is a major factor affecting the reproducibility of crystallization conditions. Drop stability can be enhanced by chemical patterning to more effectively pin the drop's contact line. As an example, a hydrophilic area is patterned on an initially flat hydrophobic glass slide. The drop remains confined to the hydrophilic area and the maximum drop size that remains stable when the slide is rotated to the vertical position increases. This simple method is readily scalable and has the potential to significantly improve the outcomes of hanging-drop and sitting-drop crystallization. [source] Bioinspired Ribbed Nanoneedles with Robust SuperhydrophobicityADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Xi Yao Abstract The robustness of superhydrophobicity is a fundamental issue for the applications of water-repellent materials. Inspired by the hierarchical structures of water-strider legs, this work describes a new water-repellent material decorated with ribbed, conical nanoneedles, successfully achieved on the surface of copper and consisting of copper hydroxide nanoneedle arrays sculptured with nanogrooves. The behavior of water drops on an as-prepared surface under various external disturbances is investigated. It is shown in particular that squeezing and relaxing drops between two such surfaces leads to a fully reversible exploration of the solid surface by the liquid, which is distinct from other superhydrophobic surfaces. This unique character is attributed to the penetrating Cassie state that occurs at the ribbed, conical nanoneedles. The proprietary lateral nanogrooves can, not only vigorously support the enwrapped liquid-air interface when a force is applied to the drop, but also provide reliable contact lines for the easy de-pinning of the deformed interface when the force is released from the drop. The results confirm the exceptional ability of strider legs to repel water, and should help to further the design of robust water-repellent materials and miniaturized aquatic devices. [source] Examples for the integration of self-organized nanowires for functional devices by a fracture approachPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2010Dawit Gedamu Abstract Simple and versatile methods to form nanowires on microchips are of interest for fundamental research and hold the potentials for an industrial fabrication. In this review article, one of these methods based on thin film fracture will be described introducing the experimental parameters and the potential for research. The advantages of the utilization of thin film cracks as a template for the nanowire formation are numerous: nanowire generation ready with contacts, a wide ranging freedom in the choice of materials, influence on the internal structure of the nanowire or the precise positioning on a microchip. A detailed discussion about the fabrication steps and some preliminary experiments revealing the possibilities of the fracture approach will be given for obtained metallic, semiconducting and anodized nanowires. In contrast to their macroscopic counterparts, the conductivity through the nanowires is entirely different. The influence of the surrounding gas atmospheres and the application of electrical fields demonstrate the applicability of these nanowires fabricated by using such a fracture approach. Perspective scanning electron microscopy micrograph of Au nanowires fabricated by thin film fracture approach between Au contact lines. The wires form a zigzag pattern on the thermally oxidized layer substrate on a silicon chip. [source] | |||||||||||||