![]() ![]() Hydrophobic and oleophobic coatings offer several advantages. Advantages of Hydrophobic & Oleophobic Coatings This means all oleophobic surfaces are also hydrophobic, while some hydrophobic surfaces are not oleophobic. Contact angles between 105° and 120° indicate an oleophobic surface. As a rule of thumb, if the contact angle with deionized water is greater than 90°, the surface is hydrophobic. The contact angle for a droplet of deionized water can also be used to indicate oleophobicity. With n-hexadecane, a standard short-chain alkane testing fluid, contact angles between 60° and 80° indicate an oleophobic. Oleophobic coatings can be characterized by the contact angle of a droplet of short-chain alkane on a surface. So, oleophobic surfaces must also be very non-polar. Thus, oils have a lower surface free energy-about a third of the surface free energy of water. Unlike water, oil and organic fluids tend to be non-polar or only slightly polar. ![]() Hydrophobic versus Oleophobic CoatingsĪs their names imply, hydrophobic coatings shed water while oleophobic coatings shed oils. If they are not, water molecules organize themselves into a droplet creating more liquid surface tension, a tighter droplet, and a wetting angle greater than 90°. ![]() A straightforward way of thinking about it for water is, since water is a polar molecule, wetting depends on whether the water molecules are attracted to surface molecules more than its own water molecules. The degree of wetting is determined by complex molecular interactions between the surface and liquid. Water that wets glass will leave streaks, and as the water evaporates, the salts and dirt left behind resulting in a water ring. In the case of a wetted surface, the liquid sticks, clinging to the surface, spreading. The extent to which a droplet wets a surface is characterized by the contact angle between the surface and the droplet (see Figure 1). A droplet that clings tightly to the surface is said to wet it. When a droplet of fluid rests on a flat surface in a gaseous environment, there is an adhesive force between a liquid droplet and a solid surface defined by the liquid-surface and liquid-gas interface. How Hydrophobic and Oleophobic Coatings Work Automotive, computing, life sciences, solar, and biotechnology are a few of the sectors utilizing these diverse coatings. However, since these coatings are usually optically transparent, they are used widely throughout consumer, industrial, and scientific products to improve optical surfaces’ ruggedness. Smartphones are the most well-known application for hydrophobic and oleophobic coatings. In addition to keeping the screen cleaner, eliminating the need to scrub, frequently wipe or use a solvent to remove dirt increases its longevity. Hydrophobic and oleophobic coatings prevent water and oil from wetting or sticking to the glass, making it easier to wipe away build-up. Frequent touching not only leaving the screen dirty but also reduces the device’s responsiveness and performance. Since fingers are used to activate devices with projected capacitive screens (multi-touch screens) or capacitive touch screens (single touch screens), oil and debris can build up on the surface. Most people are familiar with these coatings because of their use on smartphones. Hydrophobic/Oleophobic Coating on a Mobile Phone ![]()
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