Power-Sipping Nanotech Could Give Rise to Methuselah Batteries
Using phase-changing materials in the memory chips found in devices like cellphones could lower their power requirements so much that charging your handset could be as uncommon a task as resetting the clocks for daylight saving time. Researchers say practical applications of their findings are still a long way off, but they plan to try and push the limits even further.
Mar 14, 2011 6:00 AM PT
Researchers at the University of Illinois claim to have made a breakthrough in phase-change materials (PCM) technology that could lengthen battery life by up to two orders of magnitude, or 100 times.
The team, led by Professor Eric Pop, used carbon nanotube electrodes, it stated in a paper published in Science Magazine.
It found that the programming voltage and energy are highly scalable.
"As academic researchers, we will continue to focus on reducing the power dissipation till we reach nearly fundamental limits," Pop told TechNewsWorld.
"We think another factor of 10 lower power is possible," he added.
Details of the Experiment
PCM stores bits in the resistance of the material used.
Pop's team created a bit by placing a small amount of PCM in a nanoscale gap formed in the middle of a carbon nanotube, according to an article on the University of Illinois' website.
The team switched the bit on and off by passing small currents through the nanotube.
Single-wall and small-diameter multi-wall carbon nanotubes were used in the research instead of the metal wires that are the industry standard.
Carbon nanotubes are the smallest known conductors of electricity, according to Pop. They are also very stable, as they don't degrade like metal wires do. Further, the PCM material that serves as the bit can't be accidentally erased by electro-magnetic forces from a nearby scanner or magnet, unlike regular magnetic storage.
The minuscule size of the nanotubes -- 10,000 times smaller than the diameter of a human hair -- reduced the amount of electricity required.
Pop's team included David Estrada, Albert Liao and Feng Xiong.
What Is PCM, Anyhow?
"PCM is one of those interesting technologies -- you basically apply a voltage and chemical changes result," Jim McGregor, chief technology analyst at In-Stat, told TechNewsWorld."
IBM's been working on phase-change memory since at least 2006. Its Zurich labs offer this somewhat circular definition of the technology: PCM is a non-volatile solid-state memory technology that uses phase change materials.
That brings us to the question of what a phase change material is. The term refers to substances with a high heat of fusion that can store and release large amounts of energy when they change from the solid to the liquid state or vice versa.
Sounds very much like what ice does, no? There are several types of PCMs -- organic, inorganic, eutectic, and hygroscopic.
Paraffin is an organic PCM; salt hydrates are inorganic PCMs. Eutectics can be organic or a combination of organic and inorganic materials. They consist of a mixture of chemical compounds or elements that have one single chemical composition. One example is eutectic alloys for soldering, consisting of tin and lead. Hygroscopic materials absorb and release water, liberating energy in the process. Wool insulation is one hygroscope material used in buildings.
PCM offers good data retention and scalability performance, and can scale to ultra-small dimensions.
Uses for PCM
PCM can be employed in batteries. It can also be used as a replacement for hard drives, flash (solid-state drives) and maybe even RAM chips, Pop said.
"People have been looking at PCM for some time, because they're hoping it will deal with the limitations of flash memory, In-Stat's McGregor said.
PCM may go head to head with another technology -- Racetrack memory -- that IBM's been working on.
Racetrack memory has data racing around a wire "track," using the spin of the electron to store data. There are no parts to wear out, and racetrack memory can be rewritten repeatedly without any wear and tear, unlike conventional memory.
"It's likely that racetrack memory will compete to some extent with PCM," Rob Enderle, principal analyst at the Enderle Group, told TechNewsWorld. "The two appear to have similar uses."
Getting to the Money
Several obstacles remain before PCM technology actually hits the market.
"It could be about 10 years, but some challenges about mass-production of carbon nanotubes for circuits must be worked out first," Pop said.
There are also production issues that may require 10 to 15 years of work before PCM technology can actually hit the market, Enderle said.
However, the military might get to use it earlier, as "the military has a huge need for this kind of thing and the money to spend to expedite it," Enderle opined.
Other considerations, the main one of which is cost, also come into play.
"Just like any other memory technology in our industry -- it takes billions and billions of dollars to make it competitive and bring to market, and that barrier is becoming higher and higher," In-Stat's McGregor remarked.
"So the question now is when does flash run out of steam, because the industry won't pull the money together until it's absolutely necessary," McGregor added.