Alterations to the usual glass production process, such as putting the material under stress, can introduce effects that linger even after the material hardens. While manufacturers have long exploited this phenomenon to strengthen glass, a new theory aims to get closer to understanding why it happens.
Glass is not as well understood as most materials, because it straddles the line between liquid and solid. In typical crystalline materials, molecules assemble into a set structure over the span of the entire material as the substance solidifies from a disordered liquid form. Glass, on the other hand, retains a liquid-like disorder even after it hardens.
Without a set architecture, these disordered molecules are particularly vulnerable to outside forces. If you push or pull on a substance, you create internal forces, or stress, in the material itself. Once you remove that force, you’d expect the molecules to return to equilibrium, removing the stresses. But glassy materials “remember” the long-gone force.
University of Michigan researchers have created a nanotech coating that repels liquids—even caustic acids and solvents. The material can shield textiles to create stain- and chemical-resistant garments, and can reduce drag on ships.
When applied, the coating creates a webbed surface that is up to 99 percent air. It is a mixture of rubbery plastic polydimethylsiloxane particles and liquid-resisting nanoscale cubes developed by the Air Force that contain carbon, fluorine, silicon and oxygen.
“Virtually any liquid you throw on it bounces right off without wetting it,” said Anish Tuteja, a materials science and engineering assistant professor who led the development of the product. His team’s work was published recently in the Journal of the American Chemical Society.
Top Image: The new coating here repels coffee. Image courtesy Joseph Xu/University of Michigan.