Principles of microfluidic actuation by modulation of surface stresses

Development and optimization of multifunctional devices for fluidic manipulation of films, drops, and bubbles require detailed understanding of interfacial phenomena and microhydrodynamic flows. Systems are distinguished by a large surface to volume ratio and flow at small Reynolds, capillary, and Bond numbers are strongly influenced by boundary effects and therefore amenable to control by a variety of surface treatments and surface forces. We review the principles underlying common techniques for actuation of droplets and films on homogeneous, chemically patterned, and topologically textured surfaces by modulation of normal or shear stresses

Zwitterionic nanofibers of super-glue for transparent and biocompatible multi-purpose coatings

Here we show that macrozwitterions of poly(ethyl 2-cyanoacrylate), commonly called Super Glue, can easily assemble into long and well defined fibers by electrospinning. The resulting fibrous networks are thermally treated on glass in order to create transparent coatings whose superficial morphology recalls the organization of the initial electrospun mats. These textured coatings are characterized by low liquid adhesion and anti-staining performance. Furthermore, the low friction coefficient and excellent scratch resistance make them attractive as solid lubricants. The inherent texture of the coatings positively affects their biocompatibility. In fact, they are able to promote the proliferation and differentiation of myoblast stem cells. Optically-transparent and biocompatible coatings that simultaneously possess characteristics of low water contact angle hysteresis, low friction and mechanical robustness can find application in a wide range of technological sectors, from the construction and automotive industries to electronic and biomedical devices

Magnetic properties of metallic fine particle systems

A study of the magnetic properties of metallic fine particle systems in the form of magnetic fluids has been made. The fluids were prepared utilising the organometallic decomposition route (detailed separately by N. Mason, Ph.D. thesis, Durham University 1986) and single metal systems containing Fe, Co and Ni were prepared from new precursors. The properties of the first hydrocarbon based mixed metal particle systems are also reported. For systems prepared with Fe precursors it is thought that the fine particles are not in the α-Fe phase but may be amorphous and/or consist of iron carbides. Co and Ni systems result in particles with bulk-metal like structures although Co usually forms in the f.c.c. phase. The h.c.p. is also observed. The mixed metal systems were of FeCo and Ni(_3)Fe and a tendency to form the superlattice or ordered structures was observed. In both cases Fe has been lost to the particles and this is thought to be due to the formation of volatile iron compounds during preparation and/or surfactant complexes. Narrow size distributions have been obtained in all cases with mean particle diameters in the range 4-10 nm and standard deviations of between 0.8 and 1.9. The form of the size distribution has been found to be Gaussian. A study of the anisotropy of the particles using torque and magnetisation measurements has found uniaxial anisotropy with the first anisotropy constant of the order lO(^5)Jmֿ(^3).The values observed are too large to be ascribed solely to shape anisotropy. Low temperature magnetisation measurements have revealed the existence of a paramagnetic component in the fluids. Loss of magnetisation has occurred in all systems and is thought to be due to oxidation of the metal

Aspects of the geochemistry of Onverwacht Group lavas from the Barberton Greenstone Belt

Bibliography: pages 225-253.The 3540 million year old komatiitic and tholeiitic lavas in the Onverwacht Group (Barberton greenstone belt) crop out in the rugged terrain of the eastern Transvaal lowveld. The results of an investigation into the geochemistry of the lavas, mainly from the three lower Formations of the Onverwacht Group - the Lower Ultramafic Unit (LUU) - are reported. While the lavas generally show excellent textural preservation, their primary phases have usually been reconstituted to greenschist facies mineral assemblages. Although original phenocryst phases are often pseudomorphed, they can still be identified from occasionally preserved relict grains and from the secondary mineral assemblages. In this way all the major phases that occur in the various lava types could be identified. However, before the geochemical data could be used to examine the effects of partial melting and/or crystal fractionation processes in the development of the magma compositions, it was necessary to investigate which elements had been redistributed by later metamorphic and other alteration events that have occurred in the history of the lavas

Watermarks : the catalogue for home enthusiasts

Not just when tricks are revealed as tricks, but also when they become something else and materials still push one direction but then take a different turn. The wardrobe does not quite fit in your Ford Ka, the shelves are not exactly straight, the bed does not fit the mattress and the cabinets do not line up. The tension between ideals and use opens a space for re-appropriation, one that can reveal and turn its socioeconomic codes against themselves. Perhaps these are precisely the moments of friction when these ideological watermarks can be disrupted

Flow in thin regions bounded by structured and porous surfaces : applications to load bearings

The effect of surface roughness on the load capacity and friction force of hydrodynamic bearings has received considerable interest from scientists and engineers. Surfaces of most engineered materials are textured at some level either deliberately to achieve some desired effect or produced by wear and friction of surfaces. This thesis analyses the effect of surface roughness and porosity on the load capacity of hydrodynamic bearings. The surface roughness is characterized by a single sinusoidal wave function. The implementation of sinusoidal roughness model is verified using a verification problem. Reynolds lubrication theory, derived from thin-region approximations of the Navier-Stokes equations, is used as the main tool for this study. The performance of a rough slider bearing is compared with a corresponding smooth slider bearing. The presence of roughness tends to increase the load capacity of a slider bearing at high amplitudes and low wavelengths. The level-set method is used to track interfaces for problems involving multiphase flow. In general, the results show that the surface roughness influences the pressure distribution and load capacity of bearings.\u2

Real-Time Marker Level Set on GPU

International audienceLevel set methods have been extensively used to track the dynamical interfaces between different materials for physically based simulation, geometry modeling, oceanic modeling and other scientific and engineering applications. Due to the inherent Eulerian characteristics, interface evolution based on level set usually suffers from numerical diffusion, sharp feature missing and mass loss. Although some effective methods such as Particle Level Set (PLS) and Marker Level Set (MLS) have been proposed to tackle these difficulties, the complicated correction process and the high computational cost pose severe limitations for real-time applications. In this paper we provide an efficient parallel implementation of the Marker Level Set method on latest graphics hardware. Each step of the MLS method is fully mapped on GPU with an innovative combination of different computation techniques. Relying on GPU's parallelism and flexible programmability, the method provides real-time performance for large size 2D examples and moderate 3D examples, which is significantly faster than previous CPU based methods