From: Jessica Marshall, Discovery News
Published August 21, 2009 10:15 AM

Grease? New Coating Comes Clean With Water

Removing oily smudges from mirrors, countertops or fabrics usually requires some elbow grease... and a strong soap or solvent.

A new coating developed by researchers at Purdue University promises that grease stains can be wiped away with plain old water.

Incorporating this material into cleaning products, paints or sealants could reduce the need for environmentally damaging solvents and phosphate-containing detergents, the researchers say.

Phosphate detergents can kill aquatic life by allowing algae and microbes to overgrow bodies of water, suffocating other animals by consuming the dissolved oxygen.

The new coating is made by binding a water-loving molecule to a Teflon-like molecule that repels oil. This pairing makes for a surface that prevents oil from sticking to it, while also allowing it to be wet by water.

"Most surfaces that repel oils are inherently very water repellant as well. This works great for making something 'non-stick', but when the surface does get dirty, it's basically impossible to clean the oil off without using soap," said polymer scientist Ryan Hayward of the University of Massachusetts Amherst.

"Youngblood's group has introduced a clever twist to this picture by directly incorporating soap-like components in their polymer coatings," he added.

"These materials are resistant to oils but at the same time can be easily wet by water, meaning that an oil-coated surface can be cleaned simply by rinsing with water. If these polymers can be made into robust coatings or fabrics, they could have real potential for reducing the amount of detergent that we use."

The first generation of the material was complicated and expensive to make. It took a graduate student about a week under stringent conditions to coat a piece of glass, Youngblood said.

The latest work simplifies the process, creating a compound that can be mixed straight into a window cleaner, for instance.

"We are learning that our [new products] are not as good as our original technology, but add other benefits in terms of ease of use," Youngblood said. "One might have to make a tradeoff. "

The best quality coating might be worth the effort to apply to a telescope or camera lens (the coating also has anti-fog properties), he explained. "For consumer products, we would have another system. It doesn't work as well, maybe doesn't last as long, but it's much cheaper to produce."

While the team continues to experiment with coating formulas, a product with a shorter lifetime might be good enough for use in a window cleaner where a consumer would apply it periodically, anyway, he suggested. "Every time people clean their windows, it's going to redeposit itself. "