Friday, May 02, 2008
Scientific American: "After nearly 40 years, researchers have discovered a new type of building block for electronic circuits. And there's at least a chance it will spare you from recharging your phone every other day. Scientists at Hewlett-Packard Laboratories in Palo Alto, Calif., report in Nature that a new nanometer-scale electric switch "remembers" whether it is on or off after its power is turned off. (A nanometer is one billionth of a meter.)
Researchers believe that the memristor, or memory resistor, might become a useful tool for constructing nonvolatile computer memory, which is not lost when the power goes off, or for keeping the computer industry on pace to satisfy Moore's law, the exponential growth in processing power every 18 months.
You may dimly recall circuit diagrams from your middle school science class; those little boxes with a battery on one end and a lightbulb on the other. Ring any bells? To an electrical engineer, the battery is a capacitor—a device for storing electric charge—and the lightbulb is a resistor—an obstacle to electric current. Until now, engineers have had only one other basic element to work with—the inductor, which turns current into a magnetic field.
In 1971 researcher Leon Chua of the University of California, Berkeley, noticed a gap in that list. Circuit elements express relationships between pairs of the four electromagnetic quantities of charge, current, voltage and magnetic flux. Missing was a link between charge and flux. Chua dubbed this missing link the memristor and created a crude example to demonstrate its key property: it becomes more or less resistive (less or more conductive) depending on the amount of charge that had flowed through it."