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The enhancement of heat and mass transfer using a static electric field is an interesting process for industrial applications, due to its low energy consumption and potentially high level of evaporation rate enhancement. However, to date, this phenomenon is still not understood in the context of the evaporation of sessile drops. We synthesise the current research concerning the effect of an electric...
An experimental investigation of wetting and evaporation of sessile droplets is presented on nano-porous alumina substrates having different pore distribution (uniform, random and linearly arranged) morphologies and pore sizes (70–120nm). Firstly, the behavior of a droplet as it spreads and wets a surface is captured using high speed videography and benchmarked with the correlation given by the Tanner's...
We consider a liquid drop that spreads on a wettable surface. Different time evolutions have been observed for the base radius r depending of the relative role played by inertia, viscosity, surface tension and the wetting condition. Numerical simulations were performed to discuss the relative effect of these parameters on the spreading described by the evolution of the base radius r(t) and the spreading...
The stability of nano-scale drops is an interesting area of research that could revolutionise areas such as drug delivery, printing and nano-scale manufacturing. In this study, the generation and stability of nano-scale sized drops are investigated using molecular dynamics (MD) simulations. It is seen that in the formation and stability of small drops, thermal fluctuations play an important if not...
The effect of the fingering instabilities formation inside the spot left after nanofluid droplet drying has been investigated numerically and experimentally. The ring-shaped residual spot, well-known as the “coffee ring”, usually forms during the evaporation of a colloidal sessile droplet due to the convective mass transfer toward the three-phase contact line. The series of experiments with a water...
Lipid bilayer membranes in biological cells are an essential component of cellular infrastructure and furthermore responsible for various transductional afunctionalities. Synthetic lipid membranes can be deposited as supported lipid bilayer (SLB) on functionalized solid surfaces or, as large bilayer lipid vesicles (BLV). Such artificial lipid membranes can serve as fundamental building blocks and...
Processes controlling the dynamics of the soil–water interfacial properties have a high impact on habitat, filter, buffer, storage, and transformation functions of a soil. Besides surface roughness and chemical heterogeneity, also the dynamics of surfaces properties in soils limit the application of well established methods of wettability determination for solid materials. Numerous studies investigated...
The cooling effectiveness of spray cooling is strongly influenced by droplet size and velocity as well as by the fluid properties. To enhance the understanding of the entire process, first of all basic processes occurring in the spray have to be addressed. Therefore, in this study the heat transfer during a single drop impingement onto a dry, superheated wall is investigated numerically, and the effects...
The paper proposes a general framework allowing the analysis of wetting problems in the situation where a sessile drop is placed on a rotating substrate. Wetting of ideal, rough and chemically heterogeneous surfaces by sessile rotating droplets is treated. The effect of the line tension is considered. The problem of wetting is discussed in the framework of a variational approach. It is demonstrated...
When a colloidal solution of NaCl in aqueous gelatin is allowed to dry, it forms an aggregate showing highly intricate ramified dendritic patterns with a 4-fold symmetry, interspersed between cubic crystals of macroscopic dimensions. The multifractal nature of these aggregates hint at inhomogeneous growth processes that come into play during the process of desiccation. In this paper we propose a simple...
A method of Brownian dissipative dynamics of charged colloidal nanoparticles in microdroplet of solution deposited on plane substrate is proposed for investigation of self-assembly and self-ordering of colloids during solute evaporation. Method is based on the numerical solution of multi-scale Langevin equation for each particle, the hydrodynamic microflows approach, and droplet evaporation model...
The effect of the surface free energy of substrates such as glass slide, polymethyl methacrylate, polystyrene, polypropylene and Teflon-FEP was investigated on the shape and diameter of fullerene (C 60 ) stains which were obtained by evaporation of aqueous sodium dodecyl sulfate/fullerene dispersion drops having different SDS/C 60 fullerene compositions and different drop volumes....
When using most models of new energy saving dish-washers, one annoying thing happens: plastic dishes remain still wet after the drying cycle, whereas ceramic dishes or metal cutlery are well dry. To start understanding the different drying behavior of different materials, we conducted sessile drop evaporation experiments on substrates with dissimilar thermal conductivity, but similar wettability....
Evaporation of suspended micro-liter drops in room temperature, atmospheric conditions and in quiescent air is not controlled by liquid transport across the drop interface (phase change) but by vapor transport from the drop surface to the surrounding. The vapor transport can be decomposed into convection and diffusion. Literature assumes the convection is negligible, also the evaporation process is...
A colloidal gel containing an inorganic salt is a very interesting system. The simple process of drying a small droplet of such a solution on a solid surface produces a fascinatingly rich variety of patterns at different length scales. We create some patterns by this method, with NaCl as the inorganic salt and show that the details of their morphology depend on several factors e.g. (a) the host gel,...
The transient stage of evolution in size, temperature and composition of a droplet, which nonisothermaly condenses or evaporates in the diffusion or free-molecular regime in the atmosphere of two condensable vapors and neutral carrier gas, is considered. On this stage, both solution concentration and temperature in the droplet approach their stationary values, and the steady rate of the droplet growth...
The influence of the drying rate on pattern formation of a dried drop of whole blood is investigated. A range of relative humidity (RH) between 12.0% and 66.5% is studied. Drops of whole blood of same volume are gently deposited on microscope glass substrates. A top-view camera operates at a typical frame rate of 10 frames per second, which is sufficient to monitor the drying regime of the drop (deposition,...
Using lubrication theory, drying processes of sessile droplets of blood serum (i.e. colloids with the salt admixture) on a solid hydrophilic horizontal substrate are studied. The concentration of the solute is supposed to be high enough to ensure good adhesion and strong anchoring (pinning) of the triple line, thereby a drop is desiccating with constant base. The simulation of spatial distribution...
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