Moisture contact angle measurements will classify a surface as hydrophobic when the contact angle of the water droplet exceeds 90 degrees. Exceed the degree contact angle mark and the surface will be classified as superhydrophobic. Water will jump right off the surface as seen in this video.
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Not to be outdone, hydrophilic surfaces have benefits as well. What are hydrophilic surfaces? They are high surface energy substrates that attract water and allow wetting of the surface. They typically have a droplet contact angle measurement of less than 90 degrees. Lots of surfaces tend to be more water friendly including, glass, steel, or stainless steel and many coatings and paints. Of course test results can depend on the surface roughness and surface energy of the material you're testing.
Get Our Webinar Presentation. How do I get a surface to match my desired moisture level of moisture resistance? You don't have to make a super radical change to material or product construction in order to change the moisture performance. A great example of something that is hydrophilic is self-cleaning glass.
This special glass has been engineered and coated with a nano-sized, thin-film. Instead of allowing water to form into water droplets that bead up and roll off of the glass, this cool nanotechnology helps tiny water molecules to glide over the surface in a sheet, washing dirt or other debris away.
For an example of a hydrophobic substance, look no further than HZO technology. Our thin-film nano-coating encourages water and other liquids to bead up and roll off whatever it is applied to, be it cell phone, tablet, or tiny circuit board.
Sometimes water spreads evenly when it hits a surface; sometimes it beads into tiny droplets. While people have noticed these differences since ancient times, a better understanding of these properties, and new ways of controlling them, may bring important new applications.
Materials with a special affinity for water — those it spreads across, maximizing contact — are known as hydrophilic. Those that naturally repel water, causing droplets to form, are known as hydrophobic. Both classes of materials can have a significant impact on the performance of power plants, electronics, airplane wings and desalination plants, among other technologies, says Kripa Varanasi, an associate professor of mechanical engineering at MIT.
The characteristic property of these hydrogels is to absorb water and swell. Hydrophilic hydrogels also have a soft character along with biocompatibility. Hydrogels are copolymers or homopolymers that are prepared by crosslinking of monomers. These monomers have an ionizable group or a functional group that can be ionized.
Hydrogels may contain weakly basic groups like substituted amines, or weakly acidic groups like carboxylic acid, or strong basic and acidic groups like quaternary ammonium compounds and sulfonic acids. All these ionic groups make the hydrogels hydrophilic. Polyacrylates and sodium polyacrylates are superabsorbent hydrophilic hydrogel polymers that are used in making diapers.
These superabsorbent hydrogels can hold water equivalent to times their own weight. Hydrophilic hydrogels are similar to the extracellular matrix and for this reason, they are widely being explored for making artificial tissue scaffolds. Due to biocompatibility, hydrophilic hydrogels are widely used in biomedical applications. Gelatin is one of the widely used hydrophilic hydrogels.
Gelatin is most commonly used for preparing capsules. The hydrophilic hydrogel also helps to hasten the wound healing process and hence they are widely used as a wound-healing agent. Hydrophilic hydrogels are superabsorbent materials that are also widely used in drug-delivery systems, tissue repairing, and cosmetics. Hydrophilic super porous hydrogels are used as disintegrants or super disintegrants in a tablet for achieving fast drug release from the tablet. Hydrophilicity is a critical criterion for the absorption of a drug molecule.
It is a well-established fact that for the absorption of a drug in the human body, the drug should be in a solubilized state. Hydrophilic drugs tend to easily dissolve and are solubilized, thereby enabling drug absorption. Thus, hydrophilic drugs having suitable permeability have a higher probability of getting absorbed in the body easily and exert their therapeutic effects.
Hydrophilic substances are coated onto the surface of medical devices to reduce bacterial adhesion onto the surface of the medical device. Hydrophilic polymers like, polyvinylpyrrolidone PVP , polyurethanes, polyacrylic acid PAA , polyethylene oxide PEO , and polysaccharides are widely used as anti-fouling coatings on medical devices like catheters, stents.
As soon as any medical device is placed in the body, the deposition of the protein layer is initiated. Over a period of time, this layer becomes very thick and can result in serious side effects viz. Hence, it is necessary to circumvent the formation of the protein layer on the surface of the medical device. Hydrophilic polymers act as an anti-fouling agent and thereby resist the build-up of this protein layer over the surface of the medical device.
Additionally, these hydrophilic polymers help to reduce the coefficient of friction thereby enabling ease of installation of the medical device in the body.
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