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Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid–liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquids—organic or inorganic, polar or nonpolar, Newtonian or non-Newtonian.
A breakthrough that could have big implications for everything from stain-free clothing to protective surface coatings and chemical resistant protective suits: a s u p e r omniphobic coating that is resistant to pretty much any liquid we know of.
oped coating can dramatically reduce the intermolecular forces that normally draw the two states of matter together. These Van der Waals interaction forces are kept at a minimum. "Normally, when the two materials get close, they imbue a small positive or negative charge on each other, and as soon as the liquid comes in contact with the solid surface it will start to spread," Tuteja said. "We've drastically reduced the interaction between the surface and the droplet." With almost no incentive to spread, the droplets stay intact, interacting only with molecules of themselves, The new coating can repel virtually any liquid and could lead maintaining a spherical shape, and to breathable protective wear for soldiers and scientists, as literally bouncing off the coating. well as stain-proof garments. In this demonstration, it repels One classification of liquid that this coffee. coating repels is the so-called nonNewtonian category, which includes shampoos, custards, blood, paints, clays and printer inks, for example. These are liquids that change their viscosity depending on the forces applied to them. They differ from the Newtonians, such as water and most other liquids, whose viscosity stays the same no matter the force applied. Viscosity is a measure of a liquid's resistance to flow on the application of force, and it's sometimes thought of as its thickness. "No one's ever demonstrated the bouncing of low surface tension non- A high-speed camera captures a droplet resting on the surface of a new super-repellant surface Newtonian liquids," Tuteja said. NCM-JULY 2013 14