Nanoscale circuits based on molecules used in sunscreen lotion have led to the discovery of the 鈥渕issing link鈥� of electronics engineering 鈥� a previously mythical device known as a 鈥渕emristor鈥�.
First predicted in 1971, the memristor could help develop denser memory chips or even electronic circuits that mimic the synapses of the human brain, says who made the discovery with colleagues at Hewlett-Packard鈥檚 lab in Palo Alto, California.
Since electronics was developed, engineers have made circuits using combinations of three basic elements 鈥� resistors, capacitors and inductors.
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But in 1971, a young circuit designer called at the University of California, Berkeley, realised something was missing. He was toying with the non-linear mathematics that describes how the four variables in a circuit 鈥� voltage, current, charge and flux 鈥� behave in the three basic elements.
鈥楽heer genius鈥�
The three building blocks each relate two of the four electronic properties of circuits, creating a chain linking charge to flux via voltage and current. But his calculations showed there should be a fourth device to directly link flux and charge.
鈥淭his was a stroke of absolute, sheer genius by Chua,鈥� says Williams. 鈥淗e then worked through some complex mathematics and saw that such a device would have an unusual property: the ability to remember its past history.鈥�
Chua showed that his predicted device could remember the last voltage applied to it, and how long it had been applied. He dubbed the property 鈥渕emristance鈥� but the memristor was quietly forgotten because it was unclear how it could ever be built.
Sunblock circuits
But Williams鈥� team has now done just that, using nanoscale circuits including molecules of the active ingredient of sunscreen 鈥� titanium dioxide.
Such circuits are used to try and use small clumps of molecules to store the binary 0s and 1s of charge to work as computer memory.
However, these efforts have been dogged by bizarre electronic effects, says Williams, who has now worked out the reason. His titanium dioxide works as a memoristor 鈥� the mythical device has been found.
Chua, now close to retirement, is thrilled at the finding. 鈥淭his seminal work presents the first example of the memristor I postulated in 1971,鈥� he told New 杏吧原创. 鈥淲e can now expect many new unconventional applications, including super-dense memories and brain-like computing chips.鈥�
Electronic synapse
The way memristors handle current and voltage is startlingly similar to the way synapses between brain cells do, says Chua. Both build up voltage to a threshold before firing and letting a current pass.
Williams agrees. 鈥淭he memristor equations do a very good job of modelling the known behaviour of synapses,鈥� he says.
He is now working to find which materials make the best memristors, and why it has only been seen so far in nanoscale devices. Williams then wants to attempt to build memristor-based memories, which will store information as resistance values and therefore need no power to hold on to the data.
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