MIT researchers have found a way to extend the working life of mobile computers by drawing power from ultracapacitors rather than batteries.Ultracapacitors are still three to five years away from becoming the main power source for laptops and handhelds, although they\u2019re already used for backup power in many small consumer products, according to Joel Schindall, a professor in MIT\u2019s Department of Electrical Engineering and Computer Science. The new device is called a nanotube-enhanced ultracapacitor, or NEU.Capacitors store energy as an electrical field, which is more efficient than standard batteries that generate energy from chemical reactions. Ultracapacitors are even more efficient. The drawback is size\u2014they need to be larger than batteries to hold the same charge.MIT researchers solved this problem by taking advantage of the enormous surface area of nanotubes: molecular-scale straws of carbon atoms that enable ultracapacitors to store electrical fields at the atomic level.The new technology could shake up the computer business, where energy efficiency is becoming a selling point. (See \u201cPowering Down,\u201d Page 68.)How fast a battery charges is also important to users. A cell phone powered by MIT\u2019s ultracapacitor could completely recharge in just a few seconds.