Imagine owning a cellphone, laptop or MP3 player that’s extremely lightweight and needs to be recharged only every few months, rather than each day or two. To achieve this goal, some scientists might try to design a better battery, but one team of engineers at the University of Illinois believes that the key to making a more efficient device lies in redesigning one of the tech’s biggest power drains: memory.
The flash memory used in many of today’s electronic gadgets works by storing data bits as an electric charge. Doing that requires relatively high voltages, and it is considerably less efficient than what’s possible with a newer type of memory called phase-change materials (PCM). This technology uses the electric current running through nanowires to store data by producing heat that can “switch” the wire between two states.
Eric Pop, an electrical and computer engineering professor at University of Illinois and the project’s research leader, knows that an even more efficient type of PCM memory is possible. Instead of using metal wires, the team substituted a series of tiny, atomic chains called carbon nanotubes. It’s these tubes that they believe will change the way we access memory over the next decade. Pop’s team has already tested several hundred new memory bits and confirmed the technology requires only 1% of the power of the PCM memory we use today.
A carbon nanotube is actually just what it sounds like — a tiny tube made up of carbon atoms. The carbon forms a honeycomb pattern to make up the walls of the tube, which makes the structure strong, even though it’s only a few nanometers in diameter. In fact, the nanotubes are about the same thickness as a DNA molecule, which is 10,000 times smaller than a human hair.
Carbon nanotubes themselves are not new. Research has been ongoing for 20 years, and there are already products on the market that take advantage of their combination of strength, flexibility and light weight. This includes a new fuel filter housing for carmaker Audi’s A4 and A5 models, and some high-end tennis rackets. That combination of strength and flexibility also appeals to scientists working for NASA. They are exploring the idea of creating a carbon-nanotube cable to support a space elevator that might aid in safe and environmentally stable space travel.
But when it comes to electronic memory, Pop says what gives the nanotubes their value is that they are excellent electrical conductors. “Electrons flow on the outer walls of these tubes,” he says. “A copper wire could never shrink to this size. It would almost certainly break, and wouldn’t conduct electricity well at all.” Plus, the smaller the contact point on the memory bit, the less energy is needed to power it.
But despite all these practical applications, Pop says it will most likely be years before we see the nanotubes working in our iPods, cellphones or other electronic applications. “Carbon nanotubes are today where silicon was in the early 1960s,” says Pop. “At that time, you could get a radio made with silicon instead of a tube radio.” These transistor radios became popularized by the rise of rock music acts like Elvis and the Beatles, and created a market for portable music.
Pop and his engineers hope that the decline of the PC, and the demand for longer-lasting, more-efficient devices like phones and tablet computers will do for carbon nanotubes what the transistor radio did for silicon. But, he says there is not enough demand from consumers yet. “The nanotubes are up against a more mature competitor, silicon, than silicon was up against in the 1960s,” he says. Silicon is used in so many processes, and is affordable, while the development and research into carbon nanotubes for electronics is still new and expensive. “For nanotechnology to come in and displace silicon, there would really have to have a fundamental problem with silicon that cannot be solved,” says Pop.
In the meantime, Pop and his team are determined to see just how efficient the nanotubes can be, and they believe they can lower the required power by at least another factor of 10. “Today, we can buy watches that don’t run on batteries. We can run them by shaking our wrist, or from the heat of our arm,” says Pop. It’s science fiction now, but he believes we may one day reach the point where thermal, mechanical or solar energy in combination with the carbon nanotubes could eliminate the need for a battery altogether.