Nano-Technology

Nanowire cooling to advance cleaner, quieter refrigeration

Li Shi, assistant professor of mechanical engineering, will use his 2004 Young Investigator Award from the Office of Naval Research to research developing efficient nanowire thermoelectric coolers and generators. His new cooling method promises to tremendously advance work toward cleaner, quieter refrigeration and power generation units, as well as work toward improved semiconductors. Engineers have been working since the 1950s to create better solid-state, thermoelectric refrigeration and power generation units. The most pervasive and efficient refrigeration technology uses compression-based systems like those in building and vehicle air-conditioning units relying on Freon, which is toxic. By contrast, the less efficient, but more environmentally friendly thermoelectric-based refrigeration systems now available realize direct energy conversion between heat and electricity without moving mechanical components and hazardous working fluids. Although significantly more inefficient, they continue to be used in smaller systems such as devices to transport blood in hospitals, temperature controls in infrared night-vision cameras and high-end car seats. However, the energy efficiency of thermoelectric devices is very low.

Using silver nanoparticles to kill germs

Dr. Miguel Jose Yacaman, chemical engineering professor, has developed a new way to make silver nanoparticles and nano-silver colloids (in which fine particles of silver are dispersed throughout other materials) to take advantage of the natural antibiotic and anti-fungal properties of silver for practical use.

Silver nanoparticles are already on the market, such as in washing machines (to kill germs on clothing) and to kill germs on food. Yacaman has figured out a better way to make the particles and colloids by using different kinds of clay “templates.” His method makes it easier to apply the nanoparticles and colloids, leading to a more efficient and inexpensive use of the product.

Silver can be used in home and personal care products, food service, home building products, medical care products, and textiles. It is also an extremely effective catalyst in the production of ethylene oxide (used to produce, among other things, detergents and antifreeze) and formaldehyde. Industry produces billions of pounds of each of these each year.