In the battle against grape juice stains and ketchup splatter, parents have a new ally: a durable coating for cotton fabric that deflects liquids. Researchers assembled a multilayer molecular film made of silica nanoparticles, which are normally held together by relatively weak positive and negative charges. They strengthened the film by coating the silica with groups of atoms that react to light. Once activated with UV light, these groups formed strong, electron-sharing bonds that anchored the silica layers to fabric. The resulting coating actively repelled stains. While cotton fibers usually soak up water, scientists photographed liquid droplets bouncing right off treated cotton fabric , they report this month in Langmuir. The angle that the edge of a droplet makes when touching the coating, a measure of water-repellence, was about 155°, greater than that of car wax (90°), or Teflon (95°). The treated material's shield remained largely intact after 95 hours of punishment with organic solvents, acids, and bases, as well as 50 washing machine cycles. Though clearly sturdy and functional, the jury is still out on such fabric's comfort and style.
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