, and other portable electronic gear. The devices, developed by researchers at Purdue University, aim to remove heat by waving a small blade in alternate directions, like the motion of a classic hand-held Chinese fan (Fig. 8-1). They consume only about 1/150th as much Figure 8-1 Tiny, quiet fan that will help cool future laptop computers, mobile phones and other portable electronic gear. ENERGY TO GO-POWER GENERATION electricity as conventional fans, and they have no gears or bearings, which produce friction and heat. Because the new fans work without motors that contain magnets, they do not produce electromagnetic "noise" that can inter- fere with electronic signals in computer circuits. The cramped interiors of laptop computers and cell phones contain empty spaces that are too small to house conventional fans but large enough to accommodate the new fans, some of which have blades about an inch long. Placing the fans in these previously empty spaces has been shown to dramat- ically reduce the interior temperatures of laptop computers. The wiggling fans will not replace conventional fans. Instead, they will be used to enhance the cooling now provided by conventional fans and passive design features, such as heat-dissipating fins. In experiments on laptop computers, the Purdue researchers reduced the interior temperatures by as much as 8 degrees Celsius. "For a very small power expenditure, we are able to get a huge benefit," says Suresh Garimella, an asso- ciate professor of mechanical engineering at Purdue. The fans run on 2 milli- watts of electricity, or 2 1/1,000ths of 1 watt, compared with 300 milliwatts for conventional fans. The fans are moved back and forth by a "piezoelectric" ceramic material that is attached to the blade. As electricity is applied to the ceramic, it expands, causing the blade to move in one direction. Then, electricity is applied in the alternate direction, causing the ceramic material to contract and move the blade back in the opposite direction. This alternating current causes the fa