Wettability Hydrophilicity/hydrophobicity

The behavior of the adsorption and desorption of blood proteins or adhesion and proliferation of different types of mammalian cells on pol)meric materials depends on the surface characteristics such as wettability, hydrophilicity/hydrophobicity ratio, bulk chemistry, surface charge and charge distribution, surface roughness, and rigidity. 

In general, the capillary forces between two vertical walls and between two vertical cylinders are attractive when they have similar wettability (hydrophilic-hydrophilic or hydrophobic-hydrophobic) and are repulsive when they have opposite wettability (hydrophilic-hydrophobic). However, this statement is not applicable for the latter two configurations (i.e., between two floating spheres and between a spherical particle and a vertical wall). Additional parameters (for example, the size and the density of floating objects) are crucially important to determine the lateral component of the capillary force. The effect of the floating object density was particularly discussed for the latter two configurations. 

After the cleaning process, other techniques are used to prepare the surface of the substrate for coating. Some techniques include drying, surface etching, and chemical surface preparation. Examples of chemical surface preparation include the formation of an oxide layer or the monolayer assembly of an adhesion promoter on the surface. These processes modify the surface of the substrates so as to facilitate the subsequent deposition process. In surface preparation, frequently, the hydrophilic/hydrophobic character of the surface is controlled to match the coating solution properties. For example, Van Driessche et al.19 reported on improving the wettability of Ni-4at%W tapes... 

From examination of the dewetting process, the requirement for the wettable (by water) or hydrophilic surface could be defined that the contact angle of water should be below ti/2. By the same principle, a contact angle above n could be set as the requirement for the nonwettable or hydrophobic surface. The surface whose contact angle is between n and ti/2 could be viewed as the surface having amphoteric wettability or amphoteric hydrophilicity/hydrophobicity. 

In order to investigate the interaction of different types of cells in terms of the surface hydrophilicity/ hydrophobicity of polymeric materials, Chinese hamster ovaries (CHO), fibroblasts, and bovine aortic endothehal cells (EC) were cultured for 1 and 2 days on the PE wettability chemogradient surfaces. The maximum adhesion and growth of the cells appeared around a water contact angle of 50 to 55°... 

Chemogradient surface The surface whose properties such as wettability, surface charge, and hydrophilicity/hydrophobicity ratio are changed gradually along the material length. 

Properties related to the surface chemistry or surface area are hydrophilic/ hydrophobic wettability, oleophilic/oleophobic, soil repeUence, water penetration, aesthetics, antibacterial function and friction behaviour. 

Coal flotation is a physiochemical process which exploits the differences in the wettability of hydrophobic clean coal and that of hydrophilic foreign particles (Arnold and Apian, 1989 Fecko et al., 2005). It is, therefore, subject to the surface properties of coal pyrite and other types of commercially worthless material present in coal which plays a major role in determining separation of such material from coal (Luttrell and Yoon, 1994 Luttrell et al., 1994). 

Ultraviolet (UV) light irradiation of ZnO pore arrays leads to transition of the wettability from hydrophobicity to hydrophilicity. Figure 12 shows the results for the as-prepared samples kept in a dark chamber for 7 days before and after irradiation... 

When the contact surfaces are greatly different in wettability (hydrophilic quartz particles on a hydrophobic paraffin wax substrate, or mastic or graphite particles on a quartz surface), the adhesion is minimal (adhesion number equal to zero). 

Hydrophilic Refers to the ability of an atom or a molecule to engage in attractive interactions with water molecules. Substances that are ionic or can engage in hydrogen bonding are hydrophilic. Hydrophilic substances are either soluble in water or, at least, wettable. Compare hydrophobic. 

When the surfaces in contact differ sharply in wettability (hydrophilic quartz particles to a hydrophobic paraffin surface, mastic and graphite particles to a quartz surface), the adhesion reaches a minimum (the adhesion number is zero). 

Systematic analysis of the effects of surface chemistry and structure on the wettability of CNTs has shown that it is possible to control their wettability from hydrophobic to hydrophilic. An... 

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