10 June 2009—Researchers at the U.S. National Institute of Standards and Technology (NIST), in Gaithersburg, Md., report in the July 2009 issue of IEEE Electron Device Letters that they have created a low-power, inexpensive flexible memory that has the properties of a memristor. Memristors can be used to make brainlike circuits and nanoelectronic memories, because they ”remember” the amount of current that has flowed through them, and that memory is reflected in the device’s resistance.
Though these devices were first theorized in 1971, no one was able to make a practical memristor until Hewlett-Packard figured out how to do it in 2008. Producing a flexible form of memristor could make a fourth fundamental circuit element usable in implantable medical electronics where stiff, brittle silicon wouldn’t work, says Curt A. Richter, head of the Nanoelectronic Device Metrology Project at NIST’s Semiconductor Electronics Division.
”Interestingly, we didn’t originally set out to make a memristor,” says Nadine Gergel-Hackett, one of the researchers on the project. The NIST group’s original work, begun two years ago, was part of an existing program on printed and flexible electronics.
But when Hewlett-Packard reported its work on memristors last year, the NIST team immediately recognized the similarities between its own work and what the HP researchers had done. Though the NIST researchers weren’t—and still aren’t—certain of all the advantages of having flexible memristors, they were sure it couldn’t hurt. ”We changed the geometry of the devices we were making, and sure enough, we noticed memristor-like properties,” says Richter.
From the outset, Richter and Gergel-Hackett envisioned flexible memory being used in medical applications. But flexible memristors could also be used for advanced analog as well as digital memory. ”You can picture using the analog properties of the memristor to remember over time what was going on, while using other memristors to store the state at a given instant,” says Richter.