The Power Plant

Carbon Nanotubes: Flexible Battery, Computer, What Next?


A 2009 issue of Discover magazine noted that “Nanotubes can be envisioned as one-atom thick sheets of carbon that have been rolled into tubes. Researchers know that when things get that small, they act a little weird, and labs around the world are now racing to capitalize on nanotubes' strange properties. With their extraordinary strength and fascinating knack for conducting electricity and heat, nanotubes are finding applications in everything from cancer treatments to hydrogen cars. These structures of carbon may be tiny—a nanotube's diameter is about 10,000 times smaller than a human hair—but their impact on science and technology has been enormous.”

Now in 2013 researchers at New Jersey Institute of Technology ( NJIT) have developed a flexible battery made with carbon nanotubes that could potentially power electronic devices with flexible displays.

Electronic manufacturers are now making flexible organic light-emitting diode (OLED) displays, a pioneering technology that allow devices such as cell phones, tablet computers and TVs to literally fold up (Fig. 1)

Fig. 1. NJIT’s flexible battery that employs carbon nanotubes.
Fig. 1. NJIT’s flexible battery that employs carbon nanotubes.

This new battery, given its flexibility and components, can be used to power this new generation of bendable electronics. The new battery is made from carbon nanotubes and micro-particles that serve as active components -- similar to those found in conventional batteries. It is designed, though, to contain the electro-active ingredients while remaining flexible.

“This battery can be made as small as a pinhead or as large as a carpet in your living room,” says Somenath Mitra, a professor of chemistry and environmental science whose research group invented the battery. “So its applications are endless. You can place a rolled-up battery in the trunk of your electric car and have it power the vehicle.”

A patent application on the battery has been filed, and the battery will be featured in an upcoming issue of “Advanced Materials.” Mitra developed the new technology at NJIT with assistance from Zhiqian Wang, a doctoral student in chemistry.

The battery has another revolutionary potential, in that it could be fabricated at home by consumers. All one would need to make the battery is a kit comprised of electrode paste and a laminating machine. One would coat two plastic sheets with the electrode paste, place a plastic separator between the sheets and then laminate the assembly. The battery assembly would function in the same way as a double-A or a triple-A battery.

“We have been experimenting with carbon nanotubes and other leading technologies for many years at NJIT,” says Mitra, “and it’s exciting to apply leading-edge technologies to create a flexible battery that has myriad consumer applications.”

Carbon Nanotubes (CNTs)

In recent decades many allotropes and forms of carbon have been discovered and researched, including nanotubes, ball shapes, and sheets. Nanotube allotropes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material. These cylindricalcarbon molecules have unusual properties, which are valuable fornanotechnologyelectronicsoptics and other fields of materials science and technology. In particular, owing to their extraordinary thermal conductivity and mechanical and electrical properties, carbon nanotubes find applications as additives to various structural materials.

More than just a laboratory curiosity, this year researchers built the first computer whose central processor is based entirely on carbon nanotubes. The computer is slow and simple, but its creators, a group of Stanford University engineers, say it shows that carbon nanotube electronics are a viable potential replacement for silicon when it reaches its limits in ever-smaller electronic circuits. Fig. 2 shows a scanning electron microscopy image shows a section of the first-ever carbon nanotube computer.

Fig. 2. Scanning electron microscopy image showing a section of the carbon nanotube computer. The image was colored to identify different parts of the chip.
Fig. 2. Scanning electron microscopy image showing a section of the carbon nanotube computer. The image was colored to identify different parts of the chip.

The carbon nanotube processor is comparable in capabilities to the Intel 4004, that company’s first microprocessor, which was released in 1971. The computer, described in the journal Nature, runs a simple software instruction set called MIPS. It can switch between multiple tasks (counting and sorting numbers) and keep track of them, and it can fetch data from and send it back to an external memory.

The nanotube processor is made up of 142 transistors, each of which contains carbon nanotubes that are about 10 to 200 nanometer long. The Stanford group says it has made six versions of carbon nanotube computers, including one that can be connected to external hardware—a numerical keypad that can be used to input numbers for addition.

Still, some people doubt that carbon nanotubes will replace silicon. Working with carbon nanotubes is a big challenge. They are typically grown in a way that leaves them in a tangled mess, and about a third of the tubes are metallic, rather than semiconducting, which causes short-circuits.

In an engineering design conference hosted at Stanford, the director of the Microsystems Technology Office at DARPA cuased a stir by discussing the end of silicon electronics. In a keynote, Robert Colwell, former chief architect at Intel, predicted that by as early as 2020, the computing industry will no longer be able to keep making performance and cost improvements by doubling the density of silicon transistors on chips every 18 to 24 months—a feat dubbed Moore’s Law after the Intel cofounder Gordon Moore, who first observed the trend.

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