In 1971, Professor Leon Chua described and named the memristor, arguing that it should be included along with the resistor, capacitor and inductor as the fourth fundamental circuit element. The memristor has properties that cannot be duplicated by any combination of the other three elements. It is would help replace DRAM and for the human brain-like characteristics, memristor technology could one day lead to computer systems that can remember and associate patterns in a way similar to how people do [artificial intelligence and singularity related]. Faster computers and electronics that use a lot less energy are now possible.
Currently the good folk at HP Labs have exploited this to create simple data storage devices. Using memristors, they have been able to store 100 gigabits on a single die in one square centimeter. That is substantially more than the 16 gigabits for a single flash chip, and a comparable storage density to modern hard drives. In the future, HP thinks they can get that up to a terabit or more per centimeter… with the access speed of DRAM. Clearly, this will vie with other technologies such as IBM’s racetrack memory. Of course, storage is only one possible role for memristors.
Memristors could also be useful in creating analog processors. When there is a smaller change in charge, the change in resistance is also smaller. The authors suggest that this could lead to the development of transistors akin to neurons, in which increased use leads to increased conductance.
A final beauty of memristors comes from their response to decreasing size. The smaller the device, the more important memristance becomes. Conventional electronic circuits have ever increasing problems with heat and leakage at smaller sizes, but memristance is proportional to the inverse of the square of the film thickness, so smaller films mean a stronger memristance effect. By developing transistors based on memristors, we may be able to continue scaling down microprocessors for a (relatively) long time to come.
Wolfgang Porod, professor of electrical engineering at the University of Notre Dame and director of the university’s Center for Nano Science and Technology. “However, if it’s going to be 100 times better or 1,000 times better (than today’s flash), it’s very hard to say at this point.”
Williams and co-authors Dmitri B. Strukov, Gregory S. Snider and Duncan R. Stewart were able to formulate a physics-based model of a memristor and build nanoscale devices in their lab that demonstrate all of the necessary operating characteristics to prove that the memristor was real.
“This opens up a whole new door in thinking about how chips could be designed and operated,” Williams says.
Engineers could, for example, develop a new kind of computer memory that would supplement and eventually replace today’s commonly used dynamic random access memory (D-RAM). Computers using conventional D-RAM lack the ability to retain information once they are turned off. When power is restored to a D-RAM-based computer, a slow, energy-consuming “boot-up” process is necessary to retrieve data stored on a magnetic disk required to run the system.
Memristor-based computers wouldn’t require that process, using less power and possibly increasing system resiliency and reliability. Chua believes the memristor could have applications for computing, cell phones, video games – anything that requires a lot of memory without a lot of battery-power drain.
17 memristors in a row are visible on this AFM image. The memristor consists of two titanium dioxide layers connected to wires. When a current is applied to one, the resistance of the other changes. That change can be registered as data. Image credit: J.J. Yang / HP Labs
Memristor-based memory and storage has the potential to lower power consumption and provide greater resiliency and reliability in the face of power interruptions to a data center.
Another potential application of memristor technology could be the development of computer systems that remember and associate series of events in a manner similar to the way a human brain recognizes patterns. This could substantially improve today’s facial recognition technology, enable security and privacy features that recognize a complex set of biometric features of an authorized person to access personal information, or enable an appliance to learn from experience.