Superhydrophobic coating

A super-hydrophobic coating is a nanoscopic surface layer that repels water.

Makeup

Super-hydrophobic coatings can be made from many different materials. The following are known possible bases for the coating:

• Manganese Oxide Polystyrene (MnO₂/PS) nano-composite
• Zinc Oxide Polystyrene (ZnO/PS) nano-composite
• Precipitated Calcium Carbonate^[1]
• Carbon nano-tube structures
• Silica nano-coating^[2]

The silica-based coatings are perhaps the simplest to use.^{[citation needed]} They are gel-based and can be easily applied either by dipping the object into the gel or via aerosol spray. In contrast, the oxide polystyrene composites are more durable than the gel-based coatings, however the process of applying the coating is much more involved and costly. Carbon nano-tubes are also expensive and difficult to produce at this point in time. Thus, the silica-based gels remain the most economically viable option at present.

Industrial uses

In industry, super-hydrophobic coatings are used in ultra-dry, surface applications. The coating causes an almost imperceptibly thin layer of air to form on top of a surface. super-hydrophobic coatings are also found in nature: they appear on plant leaves, such as the Lotus leaf, and some insect wings causing them to repel water.^[3] The coating can be sprayed onto objects to make them waterproof. The spray is anti-corrosive and anti-icing, has cleaning capabilities and can be used to protect circuits and grids.

Super-hydrophobic coatings have important applications in maritime industry. They can yield "skin-friction drag reduction"^{[citation needed]} for ships' hulls, thus increasing fuel efficiency. Such a coating should allow ships to increase their speed and range while reducing fuel costs. They can also reduce corrosion and prevent marine organisms from growing on a ship's hull.

In addition to these industrial applications, super-hydrophobic coatings have potential uses in vehicle windshields to prevent rain droplets from clinging to the glass. The coatings also make removal of salt deposits possible without using fresh water. Furthermore, super-hydrophobic coatings have the ability to harvest other minerals from seawater brine with ease.^{[citation needed]} Despite the coatings' many applications, safety for the environment and for workers is at issue.^{[citation needed]} IMO has many regulations and policies about keeping water safe from potentially dangerous additives.

An example of the use of super-hydrophobic coatings for surface protection is "HullKote Speed Polish" — used today for smaller boats.^[4] Unlike many other polishes, this polish does not use petroleum distillates. Applying it requires only a simple wipe-on and wipe-off, without having to wait for it to dry.

Super-hydrophobic coatings also last longer than traditional coatings: over a year with one application, or more with additional coats.^{[citation needed]}

Medical applications

Due to the coating's hydrophobic and self-cleaning properties, it makes it extremely difficult for a treated surface to harbor bacteria.^[5] This allows tools and surfaces to remain sterile, even after contact with contaminating fluids. Potential applications for this include:

• Surgical tools
• Medical equipment
• Cleaning supplies
• Cotton textiles
• Substrates to prepare spherical particles for drug release
• Platforms for ex-vivo high-throughput analysis of bio-materials-cells interactions

With bacteria unable to cling to tools, equipment, and cloth, they remain sterile for much longer without needing to constantly be cleaned or replaced.

Saving money

Super-hydrophobic coatings can be applied to telephone lines, airplanes, bridges, transmission pipelines and residential plumbing to prevent corrosion and icing. The United States could save about $300^{[citation needed]} billion by using products like these to protect surfaces from fouling, condensation, friction, ice, clotting, corrosion, mildew and mold. The prices for these products range from $10 to $90 per gallon, and so could save the global market $1.13 billion.^{[citation needed]}

Consumer product brands providing such surface protection include: Super-hydrophobic Coating, Nanotechnologies, Super-hydrophobic Anti-fouling Coating, Fluorothane, and Thermablock.

References