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Nano-scale Liquid-proofing Techniques

In recent years, researchers at various universities have made quite a bit of progress in the process of coating materials to make them resistant to liquids. They hope to produce a successful liquid-proofing technique and have many applications in mind if they can achieve this goal.

Superomniphobic Coating

In 2013, a team of researchers at the University of Michigan led by Dr. Anish Tuteja released their results of a new "Superomniphobic" coating (Maly). The coating is made up of a combination of plastic particles and nanocubes that are resistant to liquids. The nanocubes are made up of Carbon, Fluorine, Silicon, and Oxygen. The researchers attach the coating to the surface they would like to coat using a process called electrospinning, in which an electric charge is used to essentially turn a nanoscale layer of materials from a liquid into a solid. The coating works largely due to its cross-linked pattern, somewhat resembling lattice. The coating is able to trap pockets of air between it and the coated material, and these air pockets are what make this method of liquid-proofing so effective. The coating ends up being about 95 to 99 percent air pockets, essentially eliminating contact between the liquid and a solid service. This sort of shield of air all but eliminates the Van der Waals forces which play a large role in why liquids will stick to whatever surface with which they interact. With this new coating, the research team has created an effective way to treat materials to be resistant to just about all liquids humans may encounter throughout their daily routine, including coffee, oil, ketchup, ink, and blood (Quick). They even tested it to be effective against the highly corrosive acid hydrochloric acid (HCl) and sodium hydroxide (NaOH). With the "blockage" of contact with the surface from the air pockets, these liquids have been shown in experiments to bounce right off of the coated materials, similar to a rubber ball bouncing off of the floor. A truly remarkable experiment, though was the one testing its effectiveness against hydrochloric acid. The team of researchers covered one side of an aluminum plate with the coating and submerged the plate in 12 M hydrochloric acid for over 25 seconds. The uncoated side is destroyed, while the coated side remained fully protected from the highly concentrated acid (Broadwith).

This new coating is more promising than old ones due to wide range of effectiveness. Previous coating have all had restrictions, whether it be that they could not resist either inorganic or organic compounds, or they struggled to resist non-Newtonian liquids. Tuteja's team has found an answer to essentially all liquids they have tested, with two minor exceptions: two chlorofluorocarbons (CFCs) that are used in refrigeration and air conditioning units. Aside from these two, the team has yet to find a liquid their coating did not resist, allowing them to boast the widest known range of liquid resistivity. In addition to this, where older coatings have simply stopped absorption, Tuteja's team's compound caused every liquid to actually bounce off of it. This could lead to many societal benefits, such as their aspirations for moisture resistant rainware, fingerprint resistant touchscreens, and liquid resistant paint used to reduce drag forces on boats. Some more scientific applications involve ultra lightweight aerogels that would be able to float on surfaces with both high surface tensions and low surface tensions (Kota). These would be able to carry around three times their own weight across these surfaces. Another scientific application is the facilitated separation of polar and non-polar liquids, which would greatly aid in the separation of, for example, oil and water. Although this is the most effective coating to date, there is one major downfall that is preventing this to becoming the full blown solution. According to Tuteja, this material can be scratched off due to the delicacies of nano-scale modification, making it mechanically impractical at the moment, so they are looking for ways to make the coating more durable, if not permanent. This may not be perfect yet, but it is the closest researchers have gotten so far.

Works Cited Broadwith, Phillip. "Superomniphobic Surface Sees off Non-Newtonian Fluids." RSC RSS. Chemistry World, 8 Jan. 2013. Web. 09 Dec. 2014. . Kota, Arun K., Gibum Kwon, and Anish Tuteja. "The Design and Applications of Superomniphobic Surfaces."Nature.com. Nature Publishing Group, 27 Feb. 2014. Web. 09 Dec. 2014. . Maly, Tim. "Superomniphobic Material Vigorously Repels All Fluids | WIRED." Wired.com. Conde Nast Digital, 30 Jan. 2013. Web. 09 Dec. 2014. . Quick, Darren. ""Superomniphobic" Nanoscale Coating Repels Almost Any Liquid." "Superomniphobic" Nanoscale Coating Repels Almost Any Liquid. Gizmag.com, 16 Jan. 2013. Web. 09 Dec. 2014. .