Wettability characteristics

Poljraer surfaces can be easily modified with microwave or radio-frequency-energized glow discharge techniques. The polymer surface cross-links or oxidizes, depending on the nature of the plasma atmosphere. Oxidizing (oxygen) and nonoxidizing (helium) plasmas can have a wide variety of effects on polymer surface wettability characteristics (92). 

Despite the fact that much effort has been made to model the DMFC system, considerable work remains, particularly in support of the emerging portable designs and systems. Few have treated the dominating effects of two-phase flow. No model to date has sufficient detail to provide a microfluidic theory for portable systems including effects of channel geometry and wettability characteristics of the GDL on fluid flow in the anode or cathode. Modeling studies are needed to fully elucidate the intricate couplings of methanol, water, and heat-transport... 

Adsorbed films of ethykriethoxysilane and vinyltriethoxy-silane were formed on silica and alumina by retraction from hydrocarbon solution and their wettabilities and water-stabilities determined. The vinyltriethoxysilane films were generally more oleophobic, more hydrophobic and more resistant to contact with water than the films formed by the ethyl analog. Neither adsorbate formed stable films on a-alumina. The addition of low molecular weight organic acids or bases to the adsorbate solution resulted in both the ethyl and vinyl compound forming hydrophobic and water-stable films on silica and ot-alumina. Films of p-chloro-phenyl-ft-ethyltrichloro, -trimethoxy, and -triethoxysilane were also studied and found to be water-stable and to have wettabilities characteristic of a surface comprised of closely-spaced p-chlorophenyl groups. 

The wettability characteristics of an adhesive/adherend pair are determined by the relative values of surface tension of the adhesive and adherend. Surface tension of a liquid is a direct measurement of intermolecular forces and is half of the free energy of molecular cohesion. Surface tension is commonly represented by -q (gamma), and is measured in dynes/cm. The value of the surface tension of the solid substrate, or adherend, is called the critical surface tension, To ensure that the surface of the adherend will be wetted by an adhesive, an adhesive whose surface tension is less than the critical surface tension should be selected, so that... 

The surfaces of devices often exhibit different wettability characteristics, depending on the manufacturing approach adopted. Surface modification techniques can be used to alter the wettability behavior of microfluidic devices. This difference in wettability can be used to control the flow rate in devices. There are many other benefits of hydrophilic surface treatments, including the ability to increase adhesion and capillary effects [2]. Irrespective of the material used in the device, the primary requirement that a material needs to fulfill is biocompatibifity in various applications. Therefore, it is also necessary to use surface modification techniques to render materials biocompatible. It is believed that future devices of increasing sophistication will often require programmable surface properties, including control of the spatial distribution of charge and polarity [3]. 

It is well known that flocculation of asphaltenes in petroleum reservoirs, wells and surface separation-upgrading facilities pose technical problems and increase the cost of production and processing of crudes. Field conditions conducive to precipitation of asphaltenes include natural depletion, miscible flooding, caustic flooding, acid stimulation and gas-lift operations. Asphaltene precipitation is particularly important problem in miscible flooding since it can reduce permeability, affect well injectivities and productivities, alter rock wettability characteristics and even cause plugging of producing wells. ... 

We now study in greater detail the surface treatments discussed in section 1.2.3.2. The standard way to apply a surface treatment is to deposit an antagonistic layer serving as an intermediary between the solid and the liquid so as to alter and possibly even reverse the wettability characteristics of the solid. 

Advances in technology have enabled microlenses to be designed and fabricated by a variety of methods. Biebuyck et al. introduced a method to form microlenses, also by utilizing surface tensions [8]. Self-assembled monolayers (SAMs) are used to pattern hydrophobic and hydrophilic regions. Water and immiscible hydrocarbon fluids (oils) exhibit different wettability characteristics in these two regions. Water droplets are segregated from hydrocarbon fluid at the surface of the SAM and thus form lenses. 

Porosity of. the Teflon core to nitrogen was 24.8 percent. The water filled pore volume was 375 cc, which corresponds to a porosity of 21 percent. The difference between the nitrogen and water porosities is attributed to the wettability characteristics of... 

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