Droplet motion on solid substrates has been widely studied not only because of its importance in fundamental research but also because of its promising potentials in droplet-based devices developed for various applica...
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Droplet motion on solid substrates has been widely studied not only because of its importance in fundamental research but also because of its promising potentials in droplet-based devices developed for various applications in chemistry, biology, and industry. In this paper, we investigate the motion of an evaporating droplet in one-component fluids on a solid substrate with a wettability gradient. As is well known, there are two major difficulties in the continuum description of fluid flows and heat fluxes near the contact line of droplets on solid substrates, namely, the hydrodynamic (stress) singularity and thermal singularity. To model the droplet motion, we use the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)] for the hydrodynamic equations in the bulk region, supplemented with the boundary conditions at the fluid-solid interface. In this continuum hydrodynamic model, various physical processes involved in the droplet motion can be taken into account simultaneously, e.g., phase transitions (evaporation or condensation), capillary flows, fluid velocity slip, and substrate cooling or heating. Due to the use of the phase field method (diffuse interface method), the hydrodynamic and thermal singularities are resolved automatically. Furthermore, in the dynamic van der Waals theory, the evaporation or condensation rate at the liquid-gas interface is an outcome of the calculation rather than a prerequisite as in most of the other models proposed for evaporating droplets. Numerical results show that the droplet migrates in the direction of increasing wettability on the solid substrates. The migration velocity of the droplet is found to be proportional to the wettability gradients as predicted by Brochard [Langmuir 5, 432 (1989)]. The proportionality coefficient is found to be linearly dependent on the ratio of slip length to initial droplet radius. These results indicate that the steady migration of the droplets results from the balance between the (cons
We found that very strong negative optical pressure can be induced in plasmonic cavities by LC resonance. This interesting effect could be described qualitatively by a Lagrangian model which shows that the negative op...
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We found that very strong negative optical pressure can be induced in plasmonic cavities by LC resonance. This interesting effect could be described qualitatively by a Lagrangian model which shows that the negative optical pressure is driven by the internal inductance and the kinetic energy of the conduction electrons. If the metal is replaced by perfect conductors, the optical pressure becomes much smaller and positive.
Cryogel based encapsulation was attempted to entrap oil phase (containing curcumin) with a ternary system of colloidal chitosan, κ-carrageenan, and carboxy methylcellulose sodium salt (NaCMC). The cryotropic gel form...
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Cryogel based encapsulation was attempted to entrap oil phase (containing curcumin) with a ternary system of colloidal chitosan, κ-carrageenan, and carboxy methylcellulose sodium salt (NaCMC). The cryotropic gel formation was investigated by varying the cooling rate during freezing and type of polymer suspension. The microstructure of the resulting curcumin cryogels revealed oil droplets entrapped in the cryogel matrix. The encapsulation yield for two types of suspension was found to vary from 83.89 to 99.37%. Controlled release of the curcumin in an aqueous system could be maintained for 4 days, and the released amount of curcumin was found to vary from 41.1-59.9%. The encapsulation yield as well as the released pattern and amount of curcumin were influenced by the cooling protocol used during freezing. The release patterns were found to be sensitive to the ambient aqueous pH and, interestingly, either a burst release or a first order release was achievable simply by changing the freezing condition. These results suggested that freezing could modify the gel formation of the present cryogel, and the resulting structural modification evidently controlled the oil encapsulation manner. The present ternary system (chitosan, κ- carrageenan, and NaCMC) is an interesting matrix for designing controlled release system in a food system.
This paper introduces a new cantilever type multi-source energy harvester generating electric power from both ambient heat and vibration. Harvesting energy from vibration was realized by electromagnetic conversion, wh...
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This paper introduces a new cantilever type multi-source energy harvester generating electric power from both ambient heat and vibration. Harvesting energy from vibration was realized by electromagnetic conversion, whereas the energy generation from heat was supplied by making use of Seebeck effect of Cr–Al thermocouples implemented on the microcantilevers. The measured average Seebeck coefficient is 12 μV/K per thermocouple. A total voltage of 3.3 mV was generated from the thermoelectric part and 13.4 mV from the electromagnetic part of the device. Measured total power from the fabricated chip is 1.91 nW (1.12 nW from vibration, 0.79 nW from thermoelectric).
This paper presents a new mechanical frequency up-conversion (FUC) mechanism for harvesting energy from external low frequency vibrations. The structure consists of a magnet placed on a support, a polystyrene cantilev...
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This paper presents a new mechanical frequency up-conversion (FUC) mechanism for harvesting energy from external low frequency vibrations. The structure consists of a magnet placed on a support, a polystyrene cantilever carrying a pick-up coil, and a mechanical barrier which converts low frequency vibrations to a higher frequency, hence increasing the efficiency of the system. The tested structure proved to give 20.3 mV and 68.7 ¿W RMS power output by up-converting 10 Hertz external vibration to 643 Hertz. The tests with different magnet configurations and cantilever lengths showed that horizontal cascading of the magnets improve the performance whereas an optimum cantilever length exits for the maximum generated power. An analytical model is also developed for the system, supporting the test results. The proposed structure is a good candidate to be realized by using microfabrication techniques in terms of generated voltage and power levels.
作者：
Arik, M.Petroski, J.Weaver, S.General Electric Company
Corporate Research and Development Energy and Propulsion Technology Laboratories Thermal Systems Laboratory One Research Circle ES-102 NiskayunaNY12309 United States General Electric Company
GELcore 6180 Halle Dr Valley ViewOH44125 United States General Electric Company
Corporate Research and Development Micro and Nano Structures Technology Lab. Electronic Structures and Materials Program One Research Circle Bldg. KW Room B1432 NiskayunaNY12309 United States
Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towar...
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Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towar...
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Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards specialty and general illumination applications. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the level-1 packages and developments in LED power packaging. The luminous efficiency of LEDs is expected to reach over 80 lumens/watt, that is approximately 6 times more than one tungsten bulb. The thermal challenges of these products in many applications will open new research areas for engineers from chip level to system level thermal management.
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