05 May 2008

True news from H-P-- memristor nano-memory element

Seems Berkeley might be hanging a new Nobel plaque above some mantel soon.

37 years ago, Dr. Leon Chua, a professor in the University of California's Electrical Engineering and Computer Sciences Department, noticed an unfilled symmetry between fundamental electromagnetic equations relating charge and flux and their corresponding passive circuit elements. He filled this blank with a conjectural passive element he termed a memristor, a device with a hysteretic (history-dependent) behavior that changes its electrical characteristics based on past current-flow history:

(Image courtesy of IEEE Spectrum's superb article on the topic.)

Chua showed that such a circuit-element could be kludged for demonstration purposes with a handful of commonplace components, but actual memristors have not been seen in the wild. Or, at least, recognized... until now, thanks to insightful work, published this month in Nature, by R. Stanley Williams, Greg Snider, Dmitri Strukov and Duncan Stewart, all of HP Labs in Palo Alto. (Williams is director of HP's Information and Quantum Systems Lab).

Turns out memristors have been created before but were unrecognized until very recently:

“People have been reporting funny current voltage characteristics in the literature for 50 years,” Williams says. “I went to these old papers and looked at the figures and said, ‘Yup, they've got memristance, and they didn't know how to interpret it.' ”

Louis Pasteur noted, "Chance favors the prepared mind," but sometimes it's the hair-raising strangeness a person encounters that sets them off on a voyage of discovery... and innovation:

...Williams and his group were working on molecular electronics when they started to notice strange behavior in their devices. “They were doing really funky things, and we couldn't figure out what [was going on],” Williams says. Then [Snider] rediscovered Chua's work from 1971. “He said, ‘Hey guys, I don't know what we've got, but this is what we want,' ” Williams remembers. Williams spent several years reading and rereading Chua's papers. “It was several years of scratching my head and thinking about it.” Then Williams realized their molecular devices were really memristors. “It just hit me between the eyes.”

And guess what, it's "green." Since the memristor's memory effect is a fundamental physical property of its construction, it heralds an era when ultra-fast information storage can be implemented on a massive scale yet consume no power except when being read or written. Contrast that with today's spinning hard disks, power-inefficient DRAM, and then reflect on the electrical appetite of something like a server farm. For example, consider Google's new site in The Dalles, Oregon: 108 Megawatts according to a hysterical Harper's, "enough to power 82,000 homes," to serve up things like "a query on 'American Idol'," a top search on Google News in 2007. Or, for a less-Luddite example than Harper's hectoring screed, consider that the sale of 20 million digital picture frames has been projected this year, each consuming about 15 Watts... 300 Megawatts! No doubt Harper's outraged author, Ginger Strand, could write a whole tract about how many warm, healthful vegan breakfasts could be cooked for starving children instead... but consider that memristors could eliminate a large chunk of both examples' power usage. Technology--and capitalism--is both the problem and the solution.

And, in case it's not already obvious from the figures and discussion so far, the discovery of demonstrable (and manufacturable) memristors is a feat of nanotechnology:

...Memristance as a property of a material was, until recently, too subtle to make use of. It is swamped by other effects, until you look at materials and devices that are mere nanometers in size. No one was looking particularly hard for memristance, either. In the absence of an application, there was no need. No engineers were saying, “If we only had a memristor, we could do X,” says [Columbia University electrical engineering professor David] Vallancourt. In fact, Vallancourt, who has been teaching circuit design for years, had never heard of memristance before this week.

Well done, gentlemen.

Practical implementation seems to be within grasp:

HP Labs is now working out how to manufacture memristors from TiO2 and other materials and figuring out the physics behind them. They also have a circuit group working out how to integrate memristors and silicon circuits on the same chip. The HP group has a hybrid silicon CMOS memristor chip “sitting on a chip tester in our lab right now,” says Williams.

But the novel behavior of memristors might open the door to entirely new computing paradigms:

In fact, he hopes to combine memristors with traditional circuit-design elements to produce a device that does computation in a non-Boolean fashion. “We won't claim that we're going to build a brain, but we want something that will compute like a brain,” Williams says. They think they can abstract “the whole synapse idea” to do essentially analog computation in an efficient manner. “Some things that would take a digital computer forever to do, an analog computer would just breeze through,” he says.

Wow. Optimism about the world ahead absolutely flows from nanotechnology. I live amid this stuff every day, and it never ceases to amaze me.

If Ginger Strand wants to pillory society's puerile fascination with American Idol, she might consider urging an episode of Idol devoted to Williams, Snider, Strukov, Stewart and Chua instead.


Anonymous said...

hi Scott,
very thoughtful and interesting post. I work at HP Labs is this is the best I've seen on the Memristor topic.
I've just posted more memristor information in my blog and have included a link to your post.
thank you for your intelligent insights.

Scott Jordan said...

Thanks very much, Jamie. Your blog is fascinating-- tons of links! Great resource. I've added a link in my Recommended Reading list on this blog.

Anonymous said...

Capitalism... Right.

Not only are you confusing Capitalism with Science: a privileged Market-booster like you won't likely grasp (anytime soon) that Capitalism has LONG outlived its usefulness to humanity -- and is on its way out. Thankfully. For the good of the planet.

And here comes Socialism, just in time too. And it will make far better use of such interesting technology than Capitalism ever could.