Last year, researchers at HP Labs built a circuit element that retains it’s memory even after the power is turned off. Named “Memristor”, short for “Memory Resistor”, this device may lead to the creation of instant-turn-on computers and analog computers that perform tasks the same way the human brain does.

Professor Leon Chua, faculty member in the Electrical Engineering and Computer Sciences Department of the University of California Berkeley, formulated and named the memristor in a paper published in 1971, stating that it should be included with the resistor, inductor and capacitor as the fourth circuit element due to it’s properties which cannot be achieved by any combination of the other three circuit elements. But neither he nor the rest of the engineering community could come up with a physical manifestation that matched his mathematical expression. Researchers had observed instances of memristance for more than 50 years, but the proof of its existence remained elusive – in part because memristance is much more noticeable in nanoscale devices.

The team that proved the existence of Chua’s memristor consists of Stanley Williams, Dmitri Strukov, Gregory Snider and Duncan Stuart. A hypothesis uptil 2008, this team was able to formulate a physics-based model for the memristor and build nanoscale devices to demonstrate all the necessary operating characteristics and prove that the memristor was real.

“This is an amazing development,” Chua says. “It took someone like Stan Williams with a multi-disciplinary background and deep insights to conceive of such a tiny memristor only a few atoms in thickness.”

Williams has a background in physical chemistry. Strukov is a theoretical physicist, Snider is a computer architect and Stewart is an experimental physicist.

According to Stanley Williams, the most interesting characteristic of the memristor is that it remembers the amount of charge that flows through it. The resistance of a memristor depends upon how much charge has gone through the device. You flow the charge in one direction and the resistance will increase. Push the charge in the opposite direction and it will decrease. Put simply, the resistance of the devices at any point in time is a function of history of the device or how much charge went through it either forwards or backwards. This simple idea will have a profound effect on computing and computer science.

“Part of what’s going to come out of this is something none of us can imagine yet,” says Williams. “But what we can imagine in and of itself is actually pretty cool.”

Memristors can make it possible to develop far more energy efficient systems with memories that retain information even when the computer power is switched off, so the user would not have to wait for the computer to boot up when turned on. It might even be possible to make computers with the pattern-matching abilities of the human brain.

Memristors might be used to supplement or replace the commonly used Dynamic Random Access Memory (D-RAM). Systems using D-RAM lack the ability to retain information when turned off. When power is restored to such a computer, it requires a slow energy-consuming boot up process to retrieve data stored on a magnetic disk and run the system. With memristors, such a process would not be necessary, reducing power-consumption and increasing system resiliency and reliability.

With regards to brain-like properties, memristor-based systems might one day be able to retain and associate patterns in a way similiar to that of humans. This could be used to improve face-recognition technology and make more complex biometric recognition systems that can restrict access to personal information more effectively. Moreover, these pattern matching abilities could help in creating appliances that learn from experience and computers with decision making capabilities.

Memristor: The Next Step In Revolutionary Electronics

For the question of when we see memristors being used commercially, the limitations are more business oriented than technological, according to Williams. The problem would be related to the time and effort involved in designing a memristor circuit.

“The money invested in circuit design is actually much larger than building fabs. In fact, you can use any fab to make these things right now, but somebody also has to design the circuits and there’s currently no memristor model. The key is going to be getting the necessary tools out into the community and finding a niche application for memristors. How long this will take is more of a business decision than a technological one.”