Machine Design

Nanocomposites From Humidifiers

Household humidifiers are now a source for more than just mildew. They are helping to create porous spheres a hundred times smaller than a red blood cell.

This is a new and inexpensive way to do chemistry using sound waves, according to researchers at the University of Illinois, Urbana-Champaign.

The complex nanocomposite materials may prove useful as catalysts in applications ranging from refining petroleum to making pharmaceuticals. "Normally, the chemical effects of ultrasound (called sonochemistry) are caused by intense heating of small gas bubbles as they collapse in an otherwise cold liquid," says Kenneth Suslick, a chemistry professor. "But in this case we are looking at ultrasound to make very small liquid droplets and heating them while they are separated from one another in a heated gas. It's the inverse of what we do sonochemically," he adds.

Researchers start with a solution of chemical reactants and surface-stabilizing surfactants. The solution is turned into a mist using a household ultrasonic humidifier. Furnaces burn away solvents and organic material, leaving behind porous inorganic nanospheres.

These nanospheres are trapped in a liquid and collected by centrifuge. The whole formation process takes only seconds.

Among the materials researchers have created with the ultrasound-induced mists are porous nanospheres that could be useful for catalytic reactions and encapsulated nanoparticles with potential drug-delivery applications.

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