University of Michigan researchers have developed a breakthrough surface material that is called "superomniphobic"-----in other words, it can just about repel any liquid! According to the engineering researchers, "A nanoscale coating that's at least 95% air repels the broadest range of liquids...causing them to bounce off the treated surface."
This groundbreaking development means that we can expect to see super-stain resistant clothing, apparel, fabric, and surfaces in the foreseeable future. The coating can also mean that garments can be made to be more "breathable" while simultaneously protecting against potentially hazardous materials; this can mean revolutionary changes in the apparel worn by both military service members as well as physicans and scientists. Moreover, there is increased possibility for paints to be more waterproof, which means less drag on ships and other vessels.
And how does this superomniphobic material work? Put simply, droplets of liquid or solution that would normally soak in and damage fabric, for instance, instead recoil once they touch the superomniphobic surface.
University of Michigan's Anish Tuteja, assistant professor of materials science and engineering, stated: "Virtually any liquid you throw on it bounces right off without wetting it."
After testing more than a 100 different liquids, only two penetrated the coating-----they were chlorofluorocarbons, such as those found in air conditioners and refrigerators. Meanwhile, amongst the liquids that could be repelled by the superomniphobic material were such things as: gasoline, alcohol, sulfuric acid, hydrochloric acid, vegetable oil, soy sauce, and coffee. The sizes of surface that were tested were small. So far only swathes of postage-stamp sized fabrics and small tiles of screen. The coating was applied with an electrospinning technique, and is made from a mixture of rubbery polydimethylsiloxane (PDMS) [which are plastic particles] and a liquid-resisting nanoscale substance [of carbon, silicon, oxygen, and fluorine] that was first developed by the US Air Force. Besides the chemistry of the superomniphobic material, its structure is likewise important to its liquid-repelling nature. Essentially, "[i]t hugs the pore structure of [the] surface it is applied to," while creating a "finer web within those pores." In this way, between 95% to 99% of the superomniphobic coating is just air pockets! Hence, when a liquid comes in contact with the superomniphobic coating it is in fact only touching few filaments of the solid surface, rather than a greater area of the solid surface!
Tuteja explains further: "Normally, when two materials get close, they imbue a small positive or small negative charge on each other, and as soon as the liquid comes in contact with the solid surface it will start to spread. [But with our superomniphobic coating,] we've drastically reduced the interaction between the surface and the droplet."
Because these droplets have "no incentive to spread," they stay intact and then only interact with themselves which makes them maintain a spherical shape, similar to the capillarity property of water droplets. The spherical shape allows these liquid droplets to better "bounce off" the superomniphobic coating.
Interestingly enough, one class of liquids that is better repelled by the superomniphobic coating is the Non-Newtonian Liquids. Non-Newtonian liquids are so-called because they change their viscosity (i.e. resistance to shape change of the liquid, and is intuitively related to the liquid's "thickness") when particular forces are applied to them. Some examples of Non-Newtonian liquids are paints, clays, blood, custard, printer ink, shampoos. By contrast, Newtonian liquids (such as water) maintain the same viscosity no matter what force is applied to them.
And so, with the superomniphobic coating, Tuteja and her fellow MSE research colleagues at the University of Michigan's engineering department have been able to "demonstrate the bouncing of low surface tension non-Newtonian liquids."