July 3, 2007&#8212Unidym, the nanotechnology company that develops high-performance, cost-effective products for the electronics industry, and majority-owned subsidiary of Arrowhead Research Corporation, has established a technical advisory board. The board, whose members are internationally recognized leaders of the scientific community with expertise ranging from nanoscale materials to printed electronics, will advise the company as it moves into its next phase of growth.

Members of the technical advisory board include Professor P. M. Ajayan, the Henry Burlage Professor of Engineering at the Rensselaer Polytechnic Institute; Professor Mike McGehee of Stanford University; George Gruner, Distinguished Professor at the University of California-Los Angeles; Professor Jin Jang of Kyung Hee University, Korea; Professor Jie Liu of Duke University; and John Rogers, Founder Professor of Engineering at the University of Illinois at Urbana-Champaign.

Unidym is focused on the manufacture and application of carbon nanotubes (CNTs) and is actively pursuing joint development and partnerships with manufacturers of touch panels, solar cells, and flat-panel displays. The company expects to execute key agreements and begin joint development work in the near future.

The American Association of Cancer Research’s recent article, “Nanoparticles Can Damage DNA, Increase Cancer Risk,” provides a good example of how researchers can unintentionally damage the public’s ability to develop a balanced understanding of nanotechnology.

The article covers research done at the University of Massachusetts and relays an interview with an undergraduate researcher, Sara Pacheco, who conducted a study on genotoxicity of two nanoparticle types. According to the article, Ms. Pacheco attributes a number of unfavorable qualities to “nanoparticles” and claims “such nanoparticles” are being used in a series of consumer goods.

Unhelpful and misleading

The article intimates that nanoparticles are a monolithic entity. As I am sure Ms. Pacheco is aware, there are vastly different nanoparticle forms, ranging from nano-metals to carbon nanotubes, buckyballs, nano-metal oxides, nano-clays, quantum dots, and several others. Even within a class such as carbon nanotubes, the number of walls, chirality, length, diameter, and surface chemistry all profoundly affect reactive properties.

Talking about “nanoparticles” is, in fact, a bit like talking about “materials”-and the statement “materials can damage DNA” is about as accurate and as informative as the article’s headline. Aside from the article’s assertion that nanoparticles are all approximately 100 nanometers in size (and certainly that is subject to debate), little can be said about them as a group. The article even admits this, stating that “very little is known about how [nanoparticles] behave,” a fact that surprisingly does not stop the author from making definitive statements about them.

As Ms. Pacheco is quoted as saying, studies like the one she and her colleagues conducted are valuable in that they improve our understanding of how a particular nanomaterial interacts with human biology. It is a mistake however, to use these findings to imply a threat from products that contain that nanomaterial. Just as there is a difference in toxic effect between drinking and inhaling water, there is a difference between holding a tennis racket with some nanotubes in the handle and directly introducing nanotubes to the DNA of cancer cells. The study neither uses the same formulations of carbon nanotubes found in consumer products, nor does it use an exposure route that represents how a consumer would come in contact with nanotubes through using the products.

In fact, in many cases where carbon nanotubes are incorporated into a matrix (like a plastic or ceramic), they bind very tightly to their surrounding and there is no evidence that they are released through use. Furthermore, most carbon nanotubes have a very high tendency to clump so that even if there existed a case where they were released, they would likely lump themselves into macro-scale carbon before contacting a cell.

Fundamentals

The article quotes the research team and Ms. Pacheco as using these findings to recommend that with nanoparticles, it is “prudent to limit their introduction into the environment.” This statement conveys a fundamental misunderstanding of the existing presence of nanoparticles in our world. Carbon nanotubes and C60 fullerene nanoparticles are produced as a by-product of most fossil fuel combustion, and sea salt on the surface of the ocean exists as a nanoparticle. We have been inhaling them and coming into contact with them ever since we discovered how to burn wood and walk to the beach-a fact that calls into question the entire culture of alarmism over the toxicity of nanomaterials. The difference is that the nanoparticles used in products have specifically been engineered to remain in the product and to be safe. If we truly want to limit our introduction of nanoparticles, our best bet would be to start using the nanocatalysts and ultra-light nano-materials that will cut down our fuel consumption.

To be fair, these issues are not isolated to this article, and I doubt there was any intent to mislead. Terms like “nano-particle” are a convenient shorthand, but there is no standard definition for them and they can be misleading. Nanotechnology holds significant promise and there are good reasons to be cautious as we proceed with it.

However, as the article admits, “there is not enough data yet” to warrant being alarmist. And we must not forget mass media’s penchant for alarmism. Scientists routinely demand precision and accuracy in research and engineering work. And it’s certainly time to make the same demand concerning communication with the public.

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Aatish Salvi is vice president of the NanoBusiness Alliance. He can be reached at [email protected].

Sean OlsonClick here to enlarge image

Through its merger with Carbon Nanotechnologies Inc. (CNI), founded by the late Richard Smalley, who won a Nobel prize for his work in nanotechnology, Unidym has assembled a full intellectual property portfolio and a range of patents covering many aspects of carbon nanotubes (CNTs).

Arrowhead Research, a publicly traded company that invested in Unidym and retains majority control, aims to assemble a complete management team, a well-stocked patent portfolio, and production capacity to make CNT-based products. Validating that strategy is the recent $16.5 million second-round investment by York Capital Management.

Unidym’s president Sean Olson (see editor’s note below) recently announced a pact with Touch Panel Laboratories of Japan to develop CNT films for handheld gaming devices. Olson tells Small Times’ Jo McIntyre how he manages the challenges of finding new markets while he’s running the merged organization.

Q: Managing industrial innovation is always challenging. What is your perspective on this? Where do you start?

You begin by focusing on which of your capabilities or assets will form the foundation for your new ideas. Whether it’s a technology platform, a customer need, or even a distribution channel, I believe it’s important to pick a starting point, even if the idea-generation process takes you someplace else.

Once you’ve come up with a few concepts, the focus should be on understanding what potential customers want. It is absolutely imperative to get out into the marketplace as quickly as you can-go to conferences, trade shows, and anywhere else you might find potential customers-and talk to them about the concept.

You will learn more from a one-hour discussion with somebody who is in one of your target markets than you will in a month of reading background materials.

Q: How do you handle the complex management structure of Unidym, CNI, and Arrowhead Research?

There was strong agreement on the strategy before the merger, so there aren’t that many management issues associated with the integration. We wanted to bring our carbon nanotube-based products to market, but knew we needed to have a stronger intellectual property position and internal production capability for our proprietary CNTs.

On CNI’s side, they realized that many of the opportunities for carbon nanotubes are ones where you don’t need a large volume of material. For them to be able to capitalize on these characteristics they knew they needed to forward-integrate into the product to capture more of the value.

What Unidym had was one specific product: transparent, conductive film of carbon nanotubes that replaces the indium tin oxide (ITO) films currently used in touch screens, flat-panel displays, OLEDs, and thin-film solar cells. It was a very good fit for what CNI wanted to do.

Q: Arrowhead starts up and operates companies through relationships they have with universities. How does that work?

There are many great technologies at universities, but not many companies are working on pulling them out into the market. That’s the opportunity for Arrowhead.

Arrowhead’s model is a bit different from the standard venture capital model. In addition to providing funding, Arrowhead maintains a controlling interest in each company and provides more management expertise and operational support, like back-office-type services, than most venture companies.

They have five subsidiaries engaged in commercializing nanotech products and applications, including anti-cancer drugs, RNAi therapeutics, carbon-based electronics, and compound semiconductor materials.

Q: How did Unidym begin?

Two years ago, John Miller of Arrowhead started Nanopolaris to assemble a toolbox of patents and productions capabilities. After about a year, the company decided there were near-term manufacturing opportunities in CNTs, so in the summer of 2006 it decided to combine with Unidym, a company that was started by UCLA professor George Grüner.

Nanopolaris took on the Unidym name and became a company with patents and a product direction-transparent conductive films and CNT-based film transistors.

Arrowhead funded the combined company with $7 million, and I got involved about three months after that.

Q: Is that where your business skills were needed?

Yes. There had been no formal management team in place. Arrowhead asked me to get involved, refine the strategy for the company, and bring in a management team. Miller got into active discussions with CNI about a merger a few months after I joined. At the outset, there was strong agreement as to what the strategy of the company should be.

Q: Do you have any customers for this product?

Yes. We sold CNT materials in 2006 to a wide range of different customers, mostly for R&D. We want to continue those relations. We expect to begin selling our transparent conductive film product in 2008. Our thin-film transistor technology leverages the work we’re doing in deposition of CNT-based films and is a second-generation product. We’re aiming for the emerging flexible display market.

Q: With Touch Panel Laboratories of Japan, for example? Do you view this as a major development, or is it just a part of your larger strategy?

It’s a collaboration with them. There is no money involved in the Touch Panel Lab joint development deal we announced in April, but we expect to have product sales in 2008. They have expertise in different touch panel markets. We are working to integrate our products into one specific area-handheld gaming applications-where they think it’s promising.

The reason CNTs are of interest there is that the primary failure mode in touch panels found in gaming devices is microcracks in the transparent conductive films that today are made of ITO. CNT films are actually a network of tiny wires that don’t degrade under repeated mechanical loading, like hitting the panel with a stylus. The CNT manufacturing technology is also less expensive, because it’s an aqueous, roll-to-roll deposition process, almost like a printing press.

Q: Does Unidym also conduct research projects, or do you farm those out to universities?

We do most of our research internally, but there are lots of experts out there doing interesting things with CNTs, and we want to develop strong relationships with them. We are funding two university projects: one at Duke with Jie Liu, who is working on carbon nanotube-based interconnects, and another at the University of Florida with Andrew Rinzler, who is working on thin-film transistors. He’s pursuing a slightly different approach than what we are doing in-house.

Q: Will you also license your many patents to other manufacturers?

Yes. We intend to use them to work with companies to bring products to market. A big driver for our merger with CNI was to get the IP base to get to market. Unidym’s patent portfolio broadly covers many other promising applications, ranging from structural composites to sensors to therapeutics. We want to partner with companies that already have capabilities in these markets.

Q: Which of these are closest to commercialization or licensing out to other manufacturers?

There are already commercial applications for carbon nanotubes in composites, and CNI is selling into that space. That is actually here and now. I believe the next big opportunity is in transparent conductive films, where we’ve got something cheaper and better than ITO films used today. Longer term, we see uses in therapeutics and drug delivery. We expect to license these, because electronics is our core capability.

Q: What do you consider the most promising direction nanotechnology research is taking these days-electronics, medicine, optics, cosmetics … ?

Electronics definitely presents the most near-term opportunities, most specifically for CNTs. As far as long-term impact, medicine would be my top pick. Arrowhead has two companies working in that space. Insert Therapeutics has developed a nano-engineered sugar that stays in the system longer for drug delivery in oncology. Calando Pharmaceuticals can engineer a delivery mechanism for siRNA therapeutics to reach their intended targets.

Q: What accomplishments are you most proud of?

I’m proud of getting myself into a role where I can help bring exciting new technologies to market. CNTs have great potential, but as with most innovations, it has taken longer than people expected. It takes a network of companies, researchers, and customers to make new technologies happen.

That critical mass is finally here for CNTs and, with the IP, the ability to produce CNTs, and a great product opportunity, we are well-positioned.

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The Olson File

Sean Olson, 36, has MS/BS degrees in mechanical engineering from Massachusetts Institute of Technology and an MBA from Harvard Business School. His technical and business experience includes positions with Silicon Valley Group Lithography, Idealab, and The Boston Consulting Group.

In 2004, he co-founded Aonex Technologies, a start-up that develops materials for the blue LED industry with a seed investment from Arrowhead Research. In November 2006, he became president of Unidym, where he will refine business strategy, hire key team members, and position the company for an IPO by the end of 2007.

Increasing microelectronic density and processing speeds imply more heat. Small tech offers next-gen solutions

By Richard Gaughan

Perhaps classifying Gordon Moore’s famous 1965 prediction-that the economically producible number of discrete components in a single IC was to double every two years-as a “Law” has given it a sense of inexorability. In fact, though, Moore’s observation was a quantification of the effects of human ingenuity in the face of a technical challenge.

And there are challenges ahead.

The average power density of advanced microcircuits is heading to several hundred Watts/cm2, creating a more difficult heat dissipation problem at the same time as small circuit dimensions lead to greater consequences of overheating. Power requirements are also an exponentially increasing function of processing speed.

If microelectronics are to continue to follow the trend of increasing density and improved processing speed, then innovative methods of dissipating heat are needed. Micro- and nano-cooling approaches are poised to meet that need.

The task of a thermal management system is to get heat out of a sensitive area and dissipate it in a large heatsink. For example, a microprocessor may be mounted with an integral radiator so that heat conducts from the electronic chip through the device to the radiator base and then radiates into the surrounding air. A circulating fan will exchange the air within the case with air from the room, which then becomes the final heatsink.

The first step is simply to get the heat from the chip to the radiator base, and the effectiveness of heat transfer depends upon the quality of the surface contact. Thermal grease is often used to ensure uniform thermal contact between the two surfaces. The better the thermal grease, the better the heat transfer.

An array of vertically aligned carbon nanotubes grown using plasma enhanced chemical vapor deposition is intercalated with copper to create a composite that exhibits good thermal properties ideal for chip cooling. (Image courtesy of NASA)Click here to enlarge image

Carbon nanotubes are the most thermally conductive material known, so what better material for enhancing thermal conductivity? That is the reasoning of Professor Minoru Taya of the University of Washington. He developed a material blend that takes advantage of both the thermal conductivity of CNTs and the mechanical flexibility of phase changeable polymer (http://depts.washington.edu/cims/research/electronic.htm). Using chloroform as an environmentally friendly solvent, the CNTs are dispersed in the polymer matrix. With the material under compression, when the polymer changes to liquid, at its specific critical temperature, the thickness decreases. Combined with the high conductivity of the CNTs, the resistance of the thermal interface material is a factor of five smaller than traditional thermal interface material.

Good thermal interfaces are useful in other places as well. For example, the Hubble Space Telescope’s Imaging Spectrograph suffered from high operating temperatures, which degraded the data quality. The problem is that surface roughness in the conductive path decreases the thermal conductivity, raising the instrument’s temperature. That may change during a proposed Hubble servicing mission next year. If approved, the material, a carpet of 40-micron-long carbon nanotubes on a copper pad, will be inserted between the two surfaces. The nanotubes, intercalated with copper, retain their structural integrity even at pressures up to 60psi. The nanotubes will conform to the rough surface, providing good thermal contact.

The intercalated CNT/copper material is also suitable for chip cooling, for which NASA has licensed the technology to a commercial partner. Meyya Meyyappan is the chief scientist for exploration at NASA’s Ames Research Center (www.ipt.arc.nasa.gov/). He spoke at NSTI’s Nanotech 2007 conference, held May 21-24 in Santa Clara, Calif., about the status of a variety of carbon nanotube applications.

This example, like all he spoke of, relies on the properties of nanomaterials to provide unique capability, but, he said, “the system itself needs a seamless integration to micro/macro for a technically feasible and commercially viable product.”

To the macro world, and beyond!

Thermal management systems are a perfect example of Meyyappan’s point. Heat may be transferred through highly conductive nanomaterial, but eventually large amounts of heat must be dissipated into the environment, the “thermal bath,” and that takes macro-scale hardware. Cooligy (www.cooligy.com), a company based in Mountain View, Calif., has developed a microstructured heat exchanger as the heart of an integrated liquid cooling system for advanced microelectronics. The company’s system approach considers not only such factors as workability of the heat exchanger material and low thermal resistance of the exchanger design, but also macroscopic factors such as efficiency of the radiator design, thermal conductivity of the cooling liquid, and even resistance to bacterial growth within the cooling loop.

Effective heat transfer in a cooling system requires the cooling fluid to be in contact with as much surface area as possible of the material that is designed to extract the heat. Fabrication of a reliable and efficient high surface-to-volume ratio microstructure (HSVRM) is therefore extremely critical for developing an effective microheat exchanger. For microchannels of the same shape, the heat transfer coefficient is inversely proportional to the hydraulic diameter. HSVRMs with very fine features in a microheat exchanger should significantly enhance heat transfer.

HSVR microstructures that are applicable in microheat exchangers can be classified into two types: microchannel and microporous. Silicon microchannels are commonly used in liquid cooling systems, although metallic materials with higher thermal conductivity are preferable for more-effective heat transfer. Folded fins are another class of microchannel HSVRMs that are used as heat exchanger structures.

Microporous types of HSVR structures provide higher values of surface area per unit volume than commonly used micro/minichannels. Mesh and woven mesh structures are ordered porous structures, while metallic foams are the most common form of unordered microporous structures. They are formed by sintering a polymeric foam substrate that is coated with slurry of metallic particles. Metal foams can also be created by electrodeposition accompanied by hydrogen evolution where metallic deposition takes place around hydrogen bubbles. The surface area of this electrochemically formed porous foam structure is several orders of magnitude higher than the other types of foams because of dendrites that form within the pores.

This image illustrates part of a series of experiments at Purdue University designed to quantify the effects of surface roughness on heat transfer. In general, increased roughness appears to offer increased heat extraction. (Image courtesy of Suresh Garimella, Purdue University)Click here to enlarge image

The problem is that small features, while they enhance the heat transfer, increase the pressure drop, levying additional requirements on the pumping system. Cooligy circumvented this problem by incorporating a manifold into the side of the heat exchanger away from the microelectronics and retaining the microstructure adjacent to the surface to be cooled. But, as Madhav Datta, Cooligy’s chief scientist, said at the recent Electrochemical Society Meeting in Chicago, “development of microheat exchangers with high heat transfer rate and minimized pressure drop is a challenging task.” Depending upon the application and required performance, the active microstructure heat exchanger design can be the porous material or the microchannel design. Coupled with a high-pressure compact mechanical pump or other pump technology, the system can maintain consistent die temperature in the presence of local hot spot zones of 1 to 2mm2, with power densities of 500W/cm2 or above. According to Fred Rebarber, director of sales and marketing, Cooligy’s process is compatible with high-volume manufacturing techniques, so costs are kept low for a technology that “offers maximized performance and reliability in a system concept that is available today for a wide range of high-end thermal management needs.”

Other commercial solutions are coming from companies such as ALD Nanosolutions, IBM, Celsia, and CoolChips (see “Aiming for a cool market,” p. 15).

Two-phase is best

The Cooling Technologies Research Center (CTRC, http://meweb.ecn.pur due.edu/~CTRC/), founded in 2002 at Purdue University, is one of the National Science Foundation’s industry/university cooperative research centers. The center’s mission is to improve the understanding and technology of high-performance heat removal from compact spaces. Air-cooled and passive heat pipe approaches generally available in commercial equipment, according to Suresh Garimella, the CTRC’s director, “have a limited ability for heat removal, and acoustic noise and space restrictions may prevent air cooling solutions from continuing. New solutions are already being called for, and a wide variety are being investigated both in the industry and universities.”

Garimella’s academic investigations into liquid cooling systems have reached the conclusion that a two-phase cooling cycle is the optimum system design for high-performance applications. In a two-phase system, the confined liquid is heated to the boiling point and then condensed, cooled, and recirculated. The latent heat of the phase transition provides a larger, well-defined heat transfer that functions at lower flow rates and smaller temperature differentials than a single-phase liquid cooling system. But the thermal performance can be influenced by several factors, including exactly where in the system the phase transition takes place, the liquid flow rate, and other conditions. The pressure requirements vary as a function of flow conditions, so design constraints on the microchannel heat exchanger, the tubing interconnections, and the pump are likely to be tighter than necessary for single-phase systems.

Several pump technologies are available, but to reach the full potential and full economic competitiveness, Garimella believes micropumps must be incorporated within the microchannel structure of the heat exchanger. No current technology is effective at that scale, but he is encouraged by the prospects for integration of electrohydrodynamic injection micropumps.

More hot technologies for cooling

Garimella noted, “We consider a wide range of approaches that span the spectrum from very high flux techniques to those that are very quiet, consume very little power, and can be incorporated into portable devices.” Other technologies that have shown promise for cooling microelectronics are piezoelectrically driven resonant fans, immersive jet-impingement cooling, and advanced heat pipe designs.

For some of these technologies, the fundamental physics is not yet well understood. But, Garimella said, “even in cases where the operational principles are understood and demonstrated, there are a lot of implementation issues, including reliability, cost, and supplier availability.” Although the addition of thermal control capabilities introduces additional design considerations, Garimella believes it is now time for thermal management to be considered simultaneously with electrical considerations in designing the next generation of electronics.

He’s encouraged by the trend within industry to use that co-design approach. “With combined electrical and thermal design, the power efficiency and self-heating problems are likely to be kept at bay for the coming decades.”