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Nanotech for Portable Electronics

Sun, 08/16/2009 - 8:00pm
Lindsay Hock

Small nanostructures could make a big appearance in major industrial and electronics applications. Although small in size, carbon nanotubes can pack a huge enhancement in strength, power, and cost. These tiny tubes can give batteries a longer shelf life, speed the performance of electronic gadgets, and work in many others applications.

The shelf life of most disposable and rechargeable batteries are relatively short, primarily because they self-discharge after they are manufactured, even before the batteries are placed into a device. As the batteries sit in a package, they lose their charge because the electrodes and electrolytes that make up the active part of the battery are co-mingled and exchange ionic charges. This condition is exacerbated by heat and the types of chemistry used to manufacture the battery. Although attempts have been made to make batteries with longer lasting shelf life, nothing seems to compare to the idea of a reserve battery.

mPhase Technologies, Little Falls, N.J., has created a reserve battery called the AlwaysReady Smart NanoBattery. Prior to activation, the electrodes and electrolytes are not combined, explains Steve Simon, the company’s Chief Technology Officer. The battery is activated by allowing the electrolyte to selectively reach the electrode chamber, which causes the chemical reaction to occur, producing voltage.

The battery could be used for emergency applications—and not be activated until needed—extending the shelf life to more than 15 years, thanks to its nanoscale design. "While other traditional reserve battery vendors make their reserve batteries very big, we make our structures smaller, using a custom silicon membrane that is porous," says Simon. The diameter of the membrane pores are on the micrometer scale, with special nano scale features located on the surface of each porous region. In addition, the top of the porous membrane is coated with a special material that repels a liquid electrolyte. In the battery’s design, if liquid is poured onto the membrane, the nano structures and the materials forming the coating of the membrane repels it, suspending the liquid with a little cushion of air underneath it. The battery is triggered through electrowetting, where a voltage pulse is applied to the liquid, which changes the physical energy characteristics on the surface of the membrane and the air surrounding the liquid electrolyte. This causes the liquid to pour through the porous membrane.

The nanofeatures are created using photolithography, where a design is patterned on a wafer of silicon. In mPhase’s case, a honeycomb design is etched through deep reactive ion etching (DRIE), where the honeycomb pores are etched through the entire silicon wafer.

Many consumers want faster startup times for computers, cell phones, and other electronic devices. Now nanotechnology can help create faster electronics and enhance the electronics/semiconductor industry.

Nantero, Woburn, Mass., speeds up electronics performance through its NRAM product, a carbon nanotube-based memory device that is nano-electromechanical.

Greg Schmergel, CEO of Nantero, describes the product as being "an actual mechanical memory where the nanotubes actually bend up and down to represent the zeros and ones; and, since the carbon nanotubes are so small—they are about 1 nm dia—we can achieve a very high density and scale the memory devices to very small sizes, down even below 5 nm." While scaling down the size of these memory devices, Nantero is also achieving very fast speeds, permanent non-volatility, and very low power consumption. As a result, Nantero provides a memory device that could potentially replace all three forms of existing memory devices known today. With NRAM, electronic applications like laptops, cell phones, blackberries, and iPods will be able to store more memory (perhaps up to 20 times what can be currently saved in these applications), according to Schmegel. The battery life of these electronics could also last longer. Maybe even one day, as Schmergel hopes, "NRAM could allow laptops to boot up instantly with no wait." And that is the beauty of nanotechnology.

Published in R & D Magazine: Vol. 51, No. 4, August, 2009, p.17.

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