A TEAM looking for new ways to store computer data have stumbled across the 鈥渕issing link鈥� of electronics: an elusive device known as the memristor.
Electronic engineers have been looking in vain for the memristor since it was back in 1971 by , then a young circuit designer at the University of California, Berkeley. Chua was studying the behaviour of resistors, capacitors and inductors 鈥� the only three passive components used in circuit design to date 鈥� when he realised something was missing.
Each of these components relates two of the four basic variables that describe the state of an electrical circuit: charge, current, voltage and magnetic flux. For example, a resistor regulates the relationship between voltage and current. Two more of the six possible combinations don鈥檛 correspond to components but are understood mathematically, leaving one pair not linked: charge and flux.
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Chua reasoned that there should be a component that directly relates the two (). 鈥淭his was a stroke of absolute, sheer genius,鈥� says , whose team at Hewlett-Packard鈥檚 lab in Palo Alto, California, has recently identified the first real memristors.
The HP team were testing a device which stores data as charged molecules held between minute wires, but their efforts were dogged by a bizarre effect: the device鈥檚 resistance seemed to vary according to the last voltage applied to it. They realised that this was just how Chua鈥檚 analysis had predicted a memristor would behave. Williams鈥檚 team now want to delve deeper into this phenomenon and find out why it is only apparent in nanoscale devices (, DOI: 10.1038/nature06932).
While 鈥渕emristance鈥� causes problems for this kind of memory storage, it might open the door to a different kind: devices that store data as resistance values, and keep it even when power is switched off. Chua is thrilled at HP鈥檚 finding, which he says鈥� adds a new dimension to nanocircuit design鈥� and should pave the way to 鈥渕any new unconventional applications鈥�.
鈥淭he memristor adds a new dimension to nanocircuit design鈥�
