Category Archives: LEDs

May 22, 2009: China-based panel maker Irico Group Electronics plans to invest $74.38 million in its first OLED production fab, which broke ground in Foshan, China on May 12, 2009, according to a report in Digitimes Displays.

Organic light emitting diodes (OLEDs) are screens based on nanostructured polymer films.

Digitimes cited China media reports as saying that construction of the OLED production fab will take about 16 months, with annual capacity to reach 12 million panels.

The reports noted that Irico also plans to build module and low-temperature polysilicon (LTPS) production lines, according to Digitimes.

The Riley Report


May 19, 2009

Flip Chips and Flashlights
by George A. Riley, Contributing Editor

With the industry’s attention riveted on the next-generation of TSV&#151enhanced stacked&#151everything 3D marvels, we sometimes forget how microelectronics are changing everyday products in our world.

When a New England ice storm left my neighborhood without electricity for a cold week last December, flashlights went from household conveniences to survival necessities. I was pleased to find that research I was aware of several years ago for applying microelectronic assembly techniques to LED packaging has led to a new world of electronic flashlights with capabilities that your grandfather’s two D-Cell electric torch can’t match.

At the 2005 SMTA Emerging Products session which I chaired, Lumileds, the high-intensity LED pioneer, presented the conference’s award-winning paper on flip chip packaging of high-power LEDs. The thermal conductivity advantage of gold stud bump assembly over solder allows higher LED operating temperatures, and therefore higher light output.

Even the lower power of small LED pocket flashlights requires careful attention to heat removal. The usual cooling problem is not just how do we remove the heat, but where do we put it? In a ring array, LEDs are distributed around the periphery of the flashlight cylinder, moving the heat sources away from the center and apart from each other, while placing them at the heatsink&#151 the aluminum case.

One might expect a beam-forming problem in this scattered arrangement, but LEDs have several beam-forming advantages over the old-fashioned bulb. The plastic lens integral with each LED can be shaped to provide a radiation pattern ranging from Lambertian (center-weighted), to a broader beam, to side-illuminating.

Beyond that, the palm-sized personal flashlights we survived with turned the potential drawback of a six-LED ring into an advantage, producing a radiation pattern perfect for our needs, but not obtainable with ordinary bulb flashlights.

While a strongly focused spotlight beam is splendid for locating distant objects, it can be awkward for stumbling around in a pitch-black cellar. Think of the difficulty of using the ultimate focused beam, a laser pointer, to navigate that cluttered space. The ideal light for that purpose would combine a focused straight-ahead main beam with a wide-angle, dimmer but diffuse light for general awareness &#151as our LED flashlights did.

The light reflector positions a flat, patterned aluminum disk behind the ring of LEDs, with the highly-reflective vertical wall of the aluminum cylinder surrounding the ring. This simultaneously provides the best of both worlds: a beam about 6 feet in diameter, and a diffuse, uniform light emitted over about160 degrees horizontally and vertically.

Finally, the overall design meets our smaller-cheaper semiconductor obsession. The one-inch diameter aluminum case with a tail- cap push switch and a removable AAA battery pack is 3.5 inches long. The flashlight fits comfortably in the palm, and conveniently in a pocket, weighting about half as much as a D-size battery.

The filament-free LED adds robustness; LED efficiency promises longer battery life. Most surprising, a package with 6 of these flashlights and 18 batteries costs less than 20 dollars, even for panicked crowds of in-the-dark buyers. Three cheers for electronic flashlights, and the microelectronic packaging that makes them possible!

Contact George Riley

May 15, 2009: Life Technologies Corp. (Nasdaq: LIFE) and Zymera Inc., have announced a licensing and supply agreement that gives Zymera rights to Life Technologies’ extensive intellectual property estate related to quantum dots.

Zymera will use Life Technologies’ Qdot nanocrystals to create new, self-illuminating quantum dot products to improve in-vivo imaging, biomarker discovery and a growing number of biosensing applications.

Pharmaceutical and biotechnology companies, as well as academic researchers, use Life Technologies’ Qdot nanocrystals for studies of the underlying basis of disease and for detecting targets in complex mixtures. These nanocrystals are nanometer-size, fluorescent particles made of semiconductor materials, which are invisible to the naked eye. These tiny particles emit intensely bright light when exposed to low-cost violet or ultraviolet light sources, displaying unique colors due to differences in size and composition.

Zymera’s novel self-illumination technology uses Bioluminescence Resonance Energy Transfer, also referred to as BRET, to transfer light from a bioluminescent protein — such as luciferase — directly to quantum dots. The resulting BRET dots produce light without an external source of illumination, eliminating autofluorescence background and the need for external light sources, such as lasers.


This image shows the tuneability of Qdot nanocrystals. Five different nanocrystal solutions are shown excited with the same long-wavelength UV lamp; the size of the nanocrystal determines the color. (Image courtesy of Life Technologies)

As a result, it is possible to visualize targets deeper in tissue sections or living animals, and to identify multiple targets at the same time with a wider variety of detection devices. Zymera expects to combine the technologies to develop new products for tracing blood and lymphatic fluid flow, tracking cells, and detecting biomarkers for use across a range of life science applications.

“This agreement enables Life Technologies to work with Zymera to expand the applications of our quantum dot technology portfolio beyond fluorescence into bioluminescence, which will enable our entry into new markets,” said Mark Stevenson, president and chief operating officer at Life Technologies

“The combination of Zymera’s technology with our fluorescent nanocrystals has the potential to create powerful solutions for the applied markets and other applications.”

“Quantum dot technology is one of the fastest-evolving technologies in life science,” said Steve Miller, vice president of commercialization at Zymera. “By licensing intellectual property from the market leader in fluorescence-based applications, we are able to advance our Zymera solutions to further unleash the potential of self-illuminating quantum dot products for more scientists to apply this technology to get a clearer picture of complex samples.”

(May 13, 2009) PISCATAWAY, NJ &#151 George G. Harman, a researcher at NIST, contributed enormously to wire bonding technology that led to an understanding of the process, and improved its reliability. His work helped transform a labor-intensive, manual procedure into the present automated, reliable process capable of producing hundreds of billions of packaged semiconductor devices/year. The IEEE with the 2009 IEEE Components, Packaging, and Manufacturing Technology Award is honoring Harman.

The award, sponsored by the IEEE Components, Packaging and Manufacturing Technology (CPMT) Society, recognizes Harman for achievements in wire bonding technologies. The award will be presented on May 28, 2009, at the 59th IEEE Electronic Components and Technology Conference in San Diego, Calif.

Wire bonding is the primary method of electrically connecting microchips and other electronics during semiconductor device assembly and packaging, where the tiny wire (as small as 18 &#181m diameter) is connected at both ends using a combination of heat, pressure and ultrasonic energy. The components that make up today’s electronic devices often contain thousands of wire-bonded interconnections to each, carrying the electrical current required to make the devices work. It is estimated that over 90% of all semiconductor devices today are interconnected via wire bonding.

Harman’s first contributions came in the defense industry. In 1968 the Poseidon strategic missile was experiencing unpredictable wire bond reliability problems. The missile contained thousands of small aluminum wire electrical connections, and if one wire failed, the entire device/system could fail. Harman investigated this problem with a goal of improving ultrasonic wire bonding and the ability to evaluate its reliability. He developed a 60- to 120-kHz floating-cone capacitor microphone system to plot the ultrasonic vibration modes of bonding tools. It was found that aspects of the tools, such as the heat produced by lights used to aid the operator’s vision, could cause the highly sensitive bond setups to move out of specification, and that vibration from the bonding machines themselves could also cause unreliable bonds. The results of this work were applied to improve process control and measurement methods and yield a better understanding of other problems in the ultrasonic bonding machines/processes.

Harman started the ASTM F-01.07 committee in 1971 to standardize wire bond testing methods and was responsible for updating these standards in 2006. He also wrote the first version of the nondestructive bond pull test used for MIL-STD-833, and his 1974 paper, “A Metallurgical Basis for the Non-Destructive Bond Pull-Test,” stands alone as the statistical and metallurgical understanding of that test method. The nondestructive bond pull test is currently required for critical space parts used by NASA.

He is well known worldwide for his books and papers on wire bonding as well as numerous 8-hour professional courses he has taught on the subject. A major contribution to the field is his book, “Wire Bonding in Microelectronics: Materials, Processes, Reliability, and Yield” which is considered the “wire bond bible” and is used by most wire bond engineers. A third edition of the book is currently being written.

An IEEE Life Fellow, he holds four patents, and his numerous awards include the IEEE Centennial Medal (1984), IEEE Third Millennium Medal (2000), Outstanding Contributions Award [David Feldman Award] (1992), IEEE CPMT Outstanding Sustained Technical Contributions Award (2001), and the U.S. Department of Commerce/National Institute of Standards and Technology (NIST) Silver (1973) and Gold (1979) medals. Harman received a bachelor’s of science from Virginia Polytechnic Institute in 1949 and a master’s of science from the University of Maryland in 1959. He was a research fellow at the University of Reading (UK) 1962–1963. He is a retired NIST Fellow, Scientist Emeritus, and consultant.

For more information, visit www.ieee.org.

May 11, 2009: For more than a decade, scientists have been frustrated in their attempts to create continuously emitting light sources from individual molecules because of an optical quirk called “blinking,” but now scientists at the University of Rochester have uncovered the basic physics behind the phenomenon, and along with researchers at the Eastman Kodak Co., created a nanocrystal that constantly emits light.

The findings, detailed online in Nature, may open the door to dramatically less expensive and more versatile lasers, brighter LED lighting, and biological markers that track how a drug interact with a cell at a level never before possible.

Many molecules, as well as crystals just a billionth of a meter in size, can absorb or radiate photons. But they also experience random periods when they absorb a photon, but instead of the photon radiating away, its energy is transformed into heat. These “dark” periods alternate with periods when the molecule can radiate normally, leading to the appearance of them turning on and off, or blinking.

“A nanocrystal that has just absorbed the energy from a photon has two choices to rid itself of the excess energy — emission of light or of heat,” says Todd Krauss, professor of chemistry at the University of Rochester and lead author on the study. “If the nanocrystal emits that energy as heat, you’ve essentially lost that energy.”

Krauss worked with engineers at Kodak and researchers at the Naval Research Laboratory and Cornell University to discover the new, non-blinking nanocrystals.

Krauss, an expert in nanocrystals, and Keith Kahen, senior principal scientist of Kodak and an expert in optoelectronic materials and devices, were exploring new types of low-cost lighting similar to organic light-emitting diodes, but which might not suffer from the short lifespans and manufacturing challenges inherent in these diodes. Kahen, with help from Megan Hahn, a postdoctoral fellow in Krauss’ laboratory, synthesized nanocrystals of various compositions.


Rendition of the new nonblinking nanocrystal. (Credit: Todd Krauss, University of Rochester)

Xiaoyong Wang, another postdoctoral fellow in Krauss laboratory, inspected one of these new nanocrystals and saw no evidence of the expected blinking phenomenon. Remarkably, even after four hours of monitoring, the new nanocrystal showed no sign of a single blink — unheard of when blinks usually happen on a scale of miliseconds to minutes.

After a lengthy investigation, Krauss and Alexander Efros from the Naval Research Laboratory concluded that the reason the blinking didn’t occur was due to the unusual structure of the nanocrystal. Normally, nanocrystals have a core of one semiconductor material wrapped in a protective shell of another, with a sharp boundary dividing the two. The new nanocrystal, however, has a continuous gradient from a core of cadmium and selenium to a shell of zinc and selenium. That gradient squelches the processes that prevent photons from radiating, and the result is a stream of emitted photons as steady as the stream of absorbed photons.

With blink-free nanocrystals, Krauss believes lasers and lighting could be incredibly cheap and easy to fabricate. Currently, different color laser light is created using different materials and processes, but with the new nanocrystals a single fabrication process can create any color laser. To alter the light color, an engineer needs only to alter the size of the nanocrystal, which Krauss says is a relatively simple task.

The same is true of what could one day be OLED’s successor, says Krauss. Essentially, “painting” a grid of differently sized nanocrystals onto a flat surface could create computer displays as thin as paper, or a wall that lights a room in any desired color.

April 21, 2009 – Renesas and NEC are reportedly mulling a merger, but traditional M&A benefits may be trumped in the interest of pure survival. Also from Japanese headlines: nervous firms ahead of quarterly results, and how chipmaking equipment firms are staying above water until the industry turns around.

NEC, Renesas chatter makes sense…or not?

Local reports are abuzz with talk that Renesas Technology and NEC, being hit hard by the current economic downturn, are in the end-stages of talks to merge their operations by the end of the new fiscal year (ending April 2010), creating the third-largest global chipmaker behind Intel and Samsung (~5.1% share vs. Intel’s 13.3% and Samsung’s 6.8%). Blending operations would, among other things, allow them to phase out older unproductive lines and better leverage economies-of-scale. (Renesas has 16 sites in Japan, twice as many as NEC, notes the Yomiuri Shimbun.) Helping the deal move along is that Renesas co-owners Hitachi and Mitsubishi Electric have indicated “they would not insist on calling the shots at the merged entity,” reported the Nikkei daily.

“If they (NEC Electronics and Renesas) are merged, that would give them benefits,” including a dominating 30% share in microcontrollers (they are 1-2) and reduced capital spending, said Haruo Sato, an analyst at Tokai Tokyo Research Center Co, quoted by Dow Jones.

Such a move not only would hoist the companies to a more prominent global position, it would also create shockwaves in Japan’s chipmaking industry, local reports note. Toshiba (currently Japan’s top chipmaker ahead of Renesas and NEC) and Fujitsu, likewise being slammed in the current environment, would be even more pressured to reshape their operations. The Kyodo News notes NEC had investigated a deal with Toshiba for a possible three-way merger with Fujitsu, but those talks were unsuccessful. Elpida, another high-profile Japanese chipmaker (its lone memory maker), is leading the consolidation of Taiwan’s memory chipmakers with government help — and may also be in line for some Japanese state-sponsored aid as well.

But not everyone sees the clear path to synergies in a NEC-Renesas combination. Assuming the two driving factors in any consolidation are cost improvement and product synergy, the highly resource- and capital-intensive chip industry isn’t well positioned to take advantage of either, notes Jim Handy of Objective analysis, in a report. New chip designs require the same general number of engineers no matter whether the company is large or small, he points out. Manufacturing costs can be improved by ramping output in fabs, but that would require significant and complex (and resource-intensive) integration of the companies’ processes. “Two companies cannot just be slapped together and see immediate, or even short-term financial benefits,” he writes. Renesas has sustained product lines of its parent companies, but more as a “co-habitation” than a consolidation, he points out. “Adding NEC to the line card may be approached the same way.”

The ultimate reasoning for consolidating chip businesses is to “lock a customer — “and usually an application category” — with all the chips needed for electronic end-equipment, Handy notes. “If one company has some key components that give another company a substantially more complete offering, then putting those two together is a strong combination and encourages design so the various components work well together.” From this key perspective, though, a Renesas-NEC combination doesn’t make as much sense, with both offering broad technologies and having significant overlap vs. new synergies. “We see little of the traditional benefits from a prospective merger between these two firms,” he summarizes.

Weathering the storm: Sony, Sumco, Toshiba

While not on the M&A front-burner (for now), other Japanese companies are definitely feeling the heat (or perhaps cold) of the bad industry climate. Some snippets, from the Nikkei daily:

  • Sony plans to transfer some development activities for image-capture devices from its Atsugi Technology Center in the greater Tokyo area to production subsidiary Sony Semiconductor Kyushu in Fukuoka Prefecture by June. The move, said to involve “several hundred engineers,” is mainly to cut operating costs, amid a corporate goal to cut expenses by ¥250B in the current fiscal year.
  • Look for Sumco to swing to a group pretax loss of ~¥40B for the three months through April 30, vs. a ¥22.6B profit a year earlier, as sales slide 65% to ¥40B. After investing ¥140B in the prior year, the company will “drastically” scale back capital outlays in the current year. Depreciation expenses are expected to rise 10% to ¥48B in the first half of the year (through September); Sumco projects a fiscal 1H09 pretax loss of ¥60B, but is offering no FY09 outlook.
  • Toshiba plans to slash semiconductor capital spending by 56% in the current fiscal year to ¥<100B, down from ¥230B last year. The company's chip unit posted better-than-expected sales of ¥1.02T were about 2% higher than expected; the segment still lost ¥250B, but that's better than it expected, thanks to steadying chip prices due to production cuts. A proposed ¥500B capital infusion targeted by June would help raise the company's capital ratio to about 13% and improve its credit rating, thus shoring up the balance sheet and steadying the company's key businesses in semiconductors as well as nuclear power plants, the Nikkei daily reported.

But there are some signs of improvement, including:

  • Tokyo Seimitsu has shaved ¥500M from its expected operating loss for the current fiscal year ending, now to ~¥2B, on ~30% lower sales of ~¥32B. Paring its workforce by ~40% is helping the bottom line, as are stronger Chinese demand for products such as dicers.
  • Orders in the April-June quarter will be up from the prior quarter, some positive news from Tokyo Electron.
  • Disco says orders for its wafer-cutting tools jumped 80% in March vs. February. It’s still projecting a -35% decline in profits to ~¥35B, and an operating loss of -¥5B, vs. a ¥100M profit for the just-ended fiscal year.

    Making the best of it

    So what to do in a lousy chip industry? Find other industries that can use your technology, ideally for better profit. And materials firms are leading the way, notes the Nikkei.

    First, a crop of firms targeting solar:

    • Kuraray plans to sell a new glass sealing material to glue cells and glass, with what it says is twice the insulating properties of conventional materials. The goal is to increase supply volumes as much as sevenfold to ¥5000 tons/year by fiscal 2011. Meanwhile, the firm has cut production of LCD panel films. With solar cell materials promising to double to ~¥4.2T LCD panel materials
    • Asahi Glass plans to invest ~¥3B for a glass processing facility in Dalian, China, where it will coat glass sheets with a thin metal membrane for thin-film solar cells — offsetting weak demand from construction and automotive markets. This comes at the expense of the company’s LCD glass substrates, where new plant operations have been postponed.
    • Mitsui Chemicals hopes to tap into the market for solar panel backsheets by turning polypropylene/polyethylene films supplier Tohcello into a wholly-owned subsidiary.
    • Toyo Ink Mfg. plans to apply its know-how in making protective films for signboards into a business targeting solar cells.
    • Equipment supplier Ebara, too, is getting into the green theme. The firm plans to use its site in Germany to sell gas processing equipment to solar panel makers in Europe, and its Shanghai operation to sell vacuum pumps to LED makers in China, notes the Nikkei Business Daily.

    And others looking at how they can tap into LEDs.

    • Later this year Tokyo Seimitsu will launch a new tool to handle LED substrates, with a tough blade to handle the metals, sapphire, and other hard materials. Price is expected to be ~¥10M, nearly half the cost of similar tools for semiconductors.
    • Disco also wants to sell more LED-cutting machines, but with lasers instead of blades, and has set up a team to develop and sell the technology. The firm hopes to double its LED-industry sales from current ¥2B-¥3B/year.

April 15, 2009: Algae is widely touted as the next best source for fueling the world’s energy needs. But one of the greatest challenges in creating biofuels from algae is that when you extract the oil from the algae, it kills the organisms, dramatically raising production costs. Now researchers at the U.S. Department of Energy’s Ames Laboratory and Iowa State University have developed groundbreaking “nanofarming” technology that safely harvests oil from the algae so the pond-based “crop” can keep on producing.

Commercialization of this new technology is at the center of a cooperative research and development agreement between the Ames Laboratory and Catilin Inc., a nanotechnology company that specializes in biofuel production. The agreement targets development of this novel approach to reduce the cost and energy consumption of the industrial processing of non-food source biofuel feedstock. The three-year project is being funded with $885,000 from DOE’s Office of Energy Efficiency and Renewable Energy, and $216,000 from Catilin and $16,000 from Iowa State University in matching funds.

The so-called “nanofarming” technology uses nanoparticles to extract oil from the algae. The process doesn’t harm the algae like other methods being developed, which helps reduce both production costs and the production cycle. Once the algal oil is extracted, a separate and proven solid catalyst from Catilin will be used to produce ASTM (American Society for Testing and Materials) and EN certified biodiesel.

The potential of algae for fuel is tremendous as up to 10,000 gallons of oil may be produced on a single acre of land. The DOE estimates that if algae fuel replaced all the petroleum fuel in the United States, it would require only 15,000 square miles, which is a few thousand square miles larger than Maryland. This is less than one-seventh the area devoted to corn production in the United States in 2000.

The driving force behind this combination of nanotechnology and biofuels is Ames Laboratory Chemical and Biological Sciences Program Director Victor Lin. Since 2000, Lin, who is also a chemistry professor at Iowa State University, has been leading research on using nanotechnology to dramatically change the production process of biodiesel. This successful technology led Lin to found Catilin one and a half years ago.

“By combining nanotechnology, chemistry and catalysis, we have been able to find solutions that have not been considered to date,” Lin said. “Ames Laboratory and Iowa State University offer valuable research capabilities and resources that will play a key role in this exciting collaboration with Catilin.”

According to Marek Pruski, Ames Laboratory senior physicist and co-investigator on the project, phase one and two of the project will cover the culturing and selection of microalgae as well as the development of the specific nanoparticle-based extraction and catalyst technologies for the removal of algal oil and the production of biodiesel, respectively. Phase three will focus on scale-up of the catalyst and pilot plant testing on conversion to biodiesel.

“When we ultimately put together this exceptional extraction technology with Catilin’s existing solid biodiesel catalyst, we will dramatically increase the reality of renewable energy,” said Catilin’s CEO, Larry Lenhart. “Given the Obama administration’s objectives, the timing is perfect.”
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April 13, 2009: NN-Labs LLC has introduced indium phosphide-based quantum dots as a new environmentally friendly, heavy metal-free, high-performance alternative to cadmium selenide-based (CdSe) quantum dots for research and teaching applications.

CdSe-based quantum dots, the current workhorse of quantum dot luminescent materials, are known to be highly toxic and environmentally hazardous but are still used widely because of the absence, until now, of alternative materials, the company said in a news release.

NN-Labs has developed a line of indium phosphide-based (InP) quantum dots, that offer high performance while eliminating the use of cadmium, a Level A toxic element with zero use tolerance for purpose-built commercial applications. NN-Labs is offering InP/ZnS core-shell quantum dots in kits of five emission colors: green (530nm), yellow (570nm), orange (600nm), red (630nm), and deep red (650nm).

Kits are available with the quantum dots dispersed in organic solvents and in water. These quantum dots are readily observed through absorption and fluorescence spectroscopy and offer similar emission color ranges to that of CdSe. In particular, these kits are designed to meet research needs requiring high performance, heavy metal-free quantum dots and teaching needs (such as experiments demonstrating spectroscopic characteristics of quantum dots.

April 13, 2009: Inlustra Technologies, a California-based startup spun out from gallium nitride (GaN) research laboratories at the University of California at Santa Barbara, has developed a scalable production process for nonpolar and semipolar GaN substrates. The company is expanding its production facilities and has recently started to fill orders from customers.

GaN semiconductor materials are critical for the production of compact and highly efficient green, blue, violet, and ultraviolet light sources. They form the basis for green LEDs for traffic signals, white LEDs as backlights for modern high-definition/high contrast displays, and blue laser diodes for Blu-Ray DVD players. GaN-based white LEDs used for general lighting are seen as a highly efficient, non-toxic replacement for fluorescent and incandescent bulbs, yielding energy savings equivalent to over 5 billion barrels of oil over the next 20 years (according to the US Dept. of Energy).

The crystal structure of GaN causes some of its properties to vary strongly with orientation. The nonpolar and semipolar planes of this structure have excited practitioners in recent years as alternatives to the conventional polar GaN c-plane, which faces some fundamental device efficiency limitations. Nonpolar and semipolar GaN promise markedly increased device performance, manufacturing yields, and device longevity compared to conventional GaN technology. While the benefits of GaN substrates are widely acknowledged, producing the material has proven challenging, especially in the nonpolar and semipolar orientations.

“Our proprietary crystal growth techniques significantly reduce the number of microscopic defects in the substrates, which will enable our customers to realize improved yields in their device production processes,” Paul Fini, CTO at Inlustra, said in a news release. The company is currently offering nonpolar GaN substrate sizes between 5×10mm and 10×20mm but will scale up its process to 2-in. over the next 9-12 months.

April 3, 2009: For the first time, MIT researchers have shown they can genetically engineer viruses to build both the positively and negatively charged ends of a lithium-ion battery.

The new virus-produced batteries have the same energy capacity and power performance as state-of-the-art rechargeable batteries being considered to power plug-in hybrid cars, and they could also be used to power a range of personal electronic devices, said Angela Belcher, the MIT materials scientist who led the research team.

The new batteries, described in the April 2 online edition of Science, could be manufactured with a cheap and environmentally benign process: The synthesis takes place at and below room temperature and requires no harmful organic solvents, and the materials that go into the battery are non-toxic.

In a traditional lithium-ion battery, lithium ions flow between a negatively charged anode, usually graphite, and the positively charged cathode, usually cobalt oxide or lithium iron phosphate. Three years ago, an MIT team led by Belcher reported that it had engineered viruses that could build an anode by coating themselves with cobalt oxide and gold and self-assembling to form a nanowire.

In the latest work, the team focused on building a highly powerful cathode to pair up with the anode, said Belcher, the Germeshausen Professor of Materials Science and Engineering and Biological Engineering. Cathodes are more difficult to build than anodes because they must be highly conducting to be a fast electrode, however, most candidate materials for cathodes are highly insulating (non-conductive).

To achieve that, the researchers, including MIT Professor Gerbrand Ceder of materials science and Associate Professor Michael Strano of chemical engineering, genetically engineered viruses that first coat themselves with iron phosphate, then grab hold of carbon nanotubes to create a network of highly conductive material. (The virii were a common bacteriophage, which infect bacteria but are harmless to humans.)

Because the viruses recognize and bind specifically to certain materials (carbon nanotubes in this case), each iron phosphate nanowire can be electrically “wired” to conducting carbon nanotube networks. Electrons can travel along the carbon nanotube networks, percolating throughout the electrodes to the iron phosphate and transferring energy in a very short time.

The team found that incorporating carbon nanotubes increases the cathode’s conductivity without adding too much weight to the battery. In lab tests, batteries with the new cathode material could be charged and discharged at least 100 times without losing any capacitance. That is fewer charge cycles than currently available lithium-ion batteries, but “we expect them to be able to go much longer,” Belcher said.


A display of MIT’s virus-built battery (the silver-colored disc), being used to power an LED. (Source: MIT)

The prototype is packaged as a typical coin cell battery, but the technology allows for the assembly of very lightweight, flexible and conformable batteries that can take the shape of their container.

Last week, MIT President Susan Hockfield took the prototype battery to a press briefing at the White House where she and US President Barack Obama spoke about the need for federal funding to advance new clean-energy technologies.

Now that the researchers have demonstrated they can wire virus batteries at the nanoscale, they intend to pursue even better batteries using materials with higher voltage and capacitance, such as manganese phosphate and nickel phosphate, said Belcher. Once that next generation is ready, the technology could go into commercial production, she said.