Ralph M. Parsons Foundation Awards $1 Million Grant to Caltech for New Research Laboratory

PASADENA, Calif.—The Ralph M. Parsons Foundation has pledged $1 million to the California Institute of Technology toward construction of a new building for chemistry and chemical engineering positioned to be the centerpiece of the Division of Chemistry and Chemical Engineering's plan for the future.

"I am delighted to thank the foundation for their commitment," said Jean-Lou Chameau, president of Caltech. "This grant represents a key component in moving a project critical to Caltech's future forward."

The new facility will be especially important in the Division's plans to further integrate teaching and research initiatives in chemistry and chemical engineering with other areas of science and engineering. The building is being named the Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering in recognition of a lead commitment toward the $35 million project from the three-degree alumnus (BS'44, MS'46, PhD'49) and his wife.

With approximately 60,000 square feet divided among three levels above ground and one basement level, the building will house seven research laboratories, one classroom and three smaller conference rooms. The Schlinger Laboratory will face San Pasqual Walk between the Noyes Laboratory of Chemical Physics and the Beckman Laboratories of Behavioral Biology, and will complete a cluster of buildings with complementary research activities.

Once constructed, the Schlinger Laboratory will support several research groups involved in projects aimed at new and synthetically useful chemical transformations with novel catalysts, the synthesis of complex organic molecules important in biology and medicine, and custom-designed polymers and nanometer-scale structures. Current plans call for the third floor to be committed entirely to organic synthesis.

The facility will house a world-class center for catalysis and chemical synthesis to be led by Nobel Laureate Robert Grubbs, the Victor and Elizabeth Atkins Professor of Chemistry. Increased space will also allow the division to bring in additional faculty who will take research in new directions, including the synthesis of pharmaceuticals and advanced materials, and the creation of alternative energy technologies.

Other scientists to move into the Schlinger Laboratory will expand our understanding of the chemistry of the atmosphere and the nature of atmospheric changes and how these changes influence the biology of the planet-an essential step in predicting how the global climate will evolve in the next few decades.

Through the years, the Parsons Foundation has provided exceptional support for both research and education at Caltech. The foundation was established in 1961 by the late Ralph M. Parsons, founder of the international engineering and construction firm that bears his name. The foundation, since 1974 a separate, free-standing, charitable organization independent of the corporation, awards grants focusing on the areas of higher education, social-impact programs, health, and civic and cultural endeavors.


Robert Tindol

Researchers Announce New Discovery about Polymers; Could Lead to Better Plastics

PASADENA, Calif.—In the late 1960s, the memorable advice given to a certain graduate of movie fame was to go into plastics. Forty years later, Caltech chemical engineering professor Julia Kornfield would like to add the word "shish-kebabs."

Shish-kebabs are beautiful, tiny structures that can form when polymers crystallize during flow. When magnified a million times they resemble a skewer running through a stack of bell peppers. Inside plastics, they make car body panels stiff and carpet fibers strong.

Shish-kebabs are responsible for the product's nice glossy finish and the hardness, but they are not without their problems. They might help you to resist a scratch, but they might also cause a layer to peel off. And that's why people want to control them.

Now, Kornfield and Yoshinobu Nozue at Sumitomo have led a team that has uncovered certain properties of shish-kebabs that should lead to improved materials in the most widely used plastics. The researchers are reporting their results in the May 18 issue of the journal Science.

"Our discovery is pertinent to the relatively strong and stiff plastics," says Kornfield. "For example, it will allow manufacturers to make polymers for complex and beautifully shaped body panels with equal or better quality than currently available-and cheaper and faster."

Shish-kebabs are made of polymers known as polyolefins, which make up half of all plastics used-over 100 million tons per year. In addition to being used for car parts, polyolefins are also used to make pipes, wire, cable, carpets, fabrics, disposable syringes, and many other things.

Polyolefins are useful because manufacturers can custom-design their properties, Kornfield explains. By varying the degree of crystallinity and the way the crystals come together, polyolefins can be altered so that they are as hard as steel or as soft as a rubber band.

"The plastics industry can tailor-make molecular distributions, but we don't know how to manipulate them," Kornfield explains. "This discovery opens up a whole new neck of the woods that people didn't know they could explore, and they'll be able to create combinations of properties you couldn't get before."

Much as an inspiring leader can influence the action of thousands, the researchers discovered, some molecules (especially long ones) can marshal many others to create the shish, which then direct the formation of kebabs. This knowledge will allow for greater control of the creation process itself.

"In other words, you could make things by injection molding that you couldn't make before, and injection molding is a very cheap, fast process-you can pop a plastic bumper for an automobile out of its mold in a couple of minutes. So you bring down the cost of manufacturing and at the same time increase the throughput."

The lead author of the paper is Shuichi Kimata, a former postdoctoral researcher in Kornfield's Caltech lab. He played a central role linking Kornfield's group at Caltech with Yoshinobu Nozue's group at Sumitomo and collaborators at the University of Tokyo.

The title of the Science paper is "Molecular Basis of the Shish-Kebab Morphology in Polymer Crystallization."


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Moore Funds Center to Facilitate Chemical Discovery

PASADENA, Calif.-Facilities to automate the work of experimental chemistry may soon accelerate the process of chemical discovery at the California Institute of Technology, thanks to a grant of over $11 million from the Gordon and Betty Moore Foundation.

The grant will establish a Center for Catalysis and Chemical Synthesis (3CS), with facilities operated by the Division of Chemistry and Chemical Engineering. The center aims to speed the invention of new catalytic reactions, much as improved robotics accelerated the Human Genome Project.

Caltech chemists have proposed several major projects that could benefit from faster experimentation. According to Victor and Elizabeth Atkins Professor of Chemistry Robert Grubbs, founding director of the center and 2005 Nobel laureate in chemistry, projects will include the development and production of medicines, new reactions for making industrial products out of biomass, and the catalytic conversion of sunlight energy into stored chemical fuels.

"The increasing demands on chemistry resulting from new drug targets from the Human Genome Project and critical environmental requirements of chemical processes require us to develop more efficient techniques for chemical discovery," Grubbs says.

Bringing together scientists from a wide variety of disciplines, the center will create two new facilities, which will share resources to promote both the rapid discovery of chemical reactions and the production of focused molecular libraries.

Like test-kitchen chefs trying variations to perfect a recipe, robotics and instruments at the facility for catalyst and reaction invention will allow investigators to rapidly survey a wide array of reaction parameters. The conventional approach is labor intensive, taking researchers' time away from the conceptual or innovative aspects of their work, so researchers have often chosen familiar syntheses rather than taking the chances that could lead to new discoveries. By making experimentation easier, the center will facilitate the exploration of higher-risk strategies.

Many of the same techniques that are used for developing new reactions can also be used to synthesize molecular libraries. Researchers use libraries for an efficient and cost-effective "shotgun" approach, performing many simultaneous tests to see what works. Yet large existing libraries are not ideal for particular applications. The focused library facility will make it easier and faster to generate small libraries designed for specific targets, allowing researchers to optimize them efficiently for their selected applications.

The Gordon and Betty Moore Foundation was established in 2000 and seeks to develop outcome-based projects that will improve the quality of life for future generations. It has organized the majority of its grant making around large-scale initiatives and concentrates funding in three program areas: environmental conservation, science, and the San Francisco Bay Area.

The foundation's $300 million California Institute of Technology commitment, combined with an additional personal gift of $300 million from Gordon and Betty Moore, make Caltech the recipient of the largest donation ever made to an institution of higher learning. Gordon Moore is an alumnus (PhD '54) and trustee of the Institute.


Written by: John Avery

Contact: Pam Pollace (415) 561-7414 pam.pollace@moore.org

Jill Perry (626) 395-3226 jperry@caltech.edu

Visit the Caltech Media Relations website at http://pr.caltech.edu/media.


Caltech and UCLA Researchers Create Memory Circuit the Size of a Human White Blood Cell

PASADENA, Calif.—Don't throw away your laptop yet, but there's a promising new high-tech invention being announced this week. Researchers have created a memory circuit the size of a white blood cell that has enough capacity to store the Declaration of Independence and have space left over. With 160 kilobits of capacity, it's the densest memory circuit ever fabricated.

Announcing the achievement in the January 25 issue of the journal Nature, the team led by chemistry professor James Heath of the California Institute of Technology says that the memory circuit is a milestone in manufacturing, even if it's not anywhere near readiness for the market.

"It's the sort of device that Intel would contemplate making in the year 2020," says Heath, who is the Gilloon Professor at Caltech. "But at the moment it furthers our goal of learning how to manufacture functional electronic circuitry at molecular dimensions."

The 2020 date assumes the validity of Moore's law, which states that the complexity of an integrated circuit will typically double every year. Current memory-cell size is .0408 square micrometers, so Moore's law assumes that the electronics industry will achieve a device density comparable to the Heath team's memory circuit in about 13 years.

However, the Caltech-UCLA team points out in their Nature article that manufacturers can see no clear way at present of extending this miniaturization beyond the year 2013. The new approach of the Heath team, therefore, will show the potential for making integrated circuits at smaller and smaller dimensions.

"Whether it's actually possible to get this new memory circuit into a laptop, I don't know," says Heath. "But we have time."

The 160,000 memory bits are arranged like a large tic-tac-toe board: 400 silicon wires crossed by 400 titanium wires, with a layer of molecular switches sandwiched between the crossing wires. Each wire crossing defines a bit, and a single bit is only 15 nanometers wide, or about one ten-thousandth the diameter of a human hair. By contrast, the most dense memory devices currently available are approximately 140 nanometers in width.

The molecular switches, called [2]rotaxanes, comprise two interlocking components—a molecular ring encircling a dumbbell-shaped molecule—that together are similar to a wedding band on a finger. When the molecular switch is electronically triggered, the ring slides between two locations on the dumbbell. Switching, then, arises from the different conductivities of the molecular switch with respect to the ring position.

Heath's group manufactured the memory circuit in a clean-room facility in their labs at Caltech, and the molecular switches were prepared by J. Fraser Stoddart, who holds UCLA's Fred Kavli Chair in Nanosystems Sciences, and his group.

The circuit has a bit density of 100 gigabit per square centimeter, which Heath's fellow lead author Jonathan Green says sets the record for integration density in a man-made object.

"We showed we can increase the density to nearly 1,000 gigabits per square centimeter, but, beyond that, there is almost no point, because you begin to run out of molecules," says Green, a Caltech graduate student in chemistry and applied physics.

The capability to manufacture electronic circuitry at such extreme dimensions opens up a host of new applications, ranging from extremely sensitive chemical and biological sensors, energy-efficient logic circuits, and a class of high-performance energy-conversion materials known as thermoelectrics.

The other lead author of the paper is Jang Wook Choi, a graduate student in chemical engineering at Caltech. The other authors are Akram Boukai, Yuri Bunimovich, Ezekiel Johnston-Halperin, Erica DeIonno, Yi Luo, Bonnie Sheriff, Ke Xu, and Young Shik Shin, all graduate students in Caltech's Division of Chemistry and Chemical Engineering, and Hsian-Rong Tseng and Stoddart, both of UCLA.

Robert Tindol
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Researchers Improve Understanding of Mechanical Properties of Carbon Nanotubes With New Computer Simulation

PASADENA, Calif.—Carbon nanotubes are tiny garden-hose-like hollow tubes that have considerable promise for future applications such as nano-sized plumbing and nanolithography, and for the creation of numerous tiny devices such as mass sensors and actuators. Such applications require improved understanding of the mechanical properties of carbon nanotubes. Previous studies pointed out that carbon nanotubes behave like macroscopic elastic hoses similar to garden hoses made of rubber.

Now, researchers at the California Institute of Technology have discovered through computer simulations that the bending of carbon nanotubes occurs differently from that of their macroscopic counterparts in significant ways. Rather than buckling immediately and squashing the hollow inner channel, the results show, the cross-section can be gradually flattened—a finding that could lead to applications in controlling the flow of fluids through real carbon nanotubes. The results are published in the current issue of the journal Physical Review Letters.

According to Konstantinos Giapis, an associate professor of chemical engineering at Caltech and lead author of the paper, the size of nanotubes that he and postdoctoral scholar Oleksandr Kutana used for the simulation are between two and seven nanometers—or less than one-ten-thousandth the diameter of a human hair. Previous studies had focused on smaller nanotubes.

When the slightly larger nanotubes are "bent" sufficiently in the simulation, Giapis explains, the walls meet when the two sides are brought close enough together, and an atomic attraction known as the van der Waals force causes the atoms of each side of the wall to stick together. This effectively clamps off the nanotube, stopping any flow of material within it until the tube is re-straightened.

"The results show that there is an intermediate regime where you can adjust the nanotube cross-section to your liking," Giapis says. "This intermediate bending regime is important for nanofluidics."

Unlike a garden hose, however, nanotubes are tiny enough to feel forces that are inconsequential in the macroscopic world. Whereas the van der Waals force is much too weak to cause the walls of a garden hose to stick together, the force should be sufficient at the microscopic level to act as a "glue" to hold the walls of nanotubes together even after the load has been partially removed.

The end result, Giapis explains, is a new understanding of how it may be possible to control microflow in the emerging world of nanotechnology. "The initial study was to understand how nanotubes bend and how their bending differs from that of macroscopic objects, but there are also practical applications.

"For future microfluidic devices, you're going to need valves," he says. These devices could include everything from pharmaceutical-delivery systems to nano-inkjet printers.

The article is available on-line at http://link.aps.org/abstract/PRL/v97/e245501.


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Chemist Nelson J. Leonard Dies

PASADENA, Calif.—Nelson J. Leonard, one of the most important chemists of the 20th century, died Monday, October 9, at his home in Pasadena, California. He was 90.

Leonard was born on September 1, 1916, in Newark, New Jersey, and attended Lehigh University in Bethlehem, Pennsylvania, before moving to Oxford University as a Rhodes Scholar. The beginning of World War II in September 1939 forced Leonard's return to the United States.

Upon his return, Leonard continued his graduate education in chemistry, concluding with a Ph.D. in 1942 from Columbia University. His research, which focused on structure establishment and partial synthesis of alstonine, a naturally occurring antimalarial compound, was performed under the direction of Robert C. Elderfield.

A postdoctoral research assistantship brought Leonard to the University of Illinois Urbana-Champaign, where he worked with professor Roger Adams on Senecio alkaloids. Teaching duties were added to his research responsibilities in 1943, and his students eventually included U.S. Navy and U.S. Army units passing through the University of Illinois. He joined a team led by professors Charles C. Price III and Harold R. Snyder engaged in research to forward the synthesis and production of the important antimalarial drug chloroquine in time for its use in the Pacific theater.

At the end of the war, during 1945 and 1946, Leonard served as a scientific consultant and special investigator in the Field Intelligence Agency Technical (FIAT), U.S. Army and U.S. Department of Commerce, European Theater. He then returned to the University of Illinois and remained on the teaching staff until his retirement in 1986. Beginning in 1992, he held the position of faculty associate in chemistry at the California Institute of Technology.

From 1943 until 1955, Leonard combined his academic work in chemistry with a flourishing musical career, as he performed as a bass-baritone soloist in choral works with the Chicago, Cleveland, and St. Louis symphony orchestras. When in 1955 Leonard was elected to membership in the National Academy of Sciences, he felt that if his peers had chosen to recognize him as a chemist, then he had "better do something about it." The heavy professional demands of chemistry would take precedence, and there would be no more singing performances.

In collaboration with professor Folke Skoog, a plant physiologist at the University of Wisconsin, Leonard carried out extensive investigations of organic compounds that initiate plant, flower, and tree growth from tissue culture, technology that is central to horticultural and agricultural development. His techniques for derivatization of nucleosides, nucleotides, and coenzymes, and to prepare fluorescent probes, placed him among the most often quoted scientists.

Over the course of his career, he published more than 400 scientific papers and trained more than 200 Ph.D. students and postdoctoral scholars. In addition to his early election to membership in the National Academy of Sciences, Leonard was a fellow of the American Academy of Arts and Sciences and a member of the American Philosophical Society. His research distinctions included the prestigious Roger Adams Award in Organic Chemistry (1981) and Arthur C. Cope Scholar Award (1995) of the American Chemical Society.

Chemistry was not the only part of Leonard's life that was interrupted by the war. Through family connections, he had met and fallen in love with Louise Cornelie Vermey of the Netherlands. They were engaged, but were not able to see each other again until the end of the war in 1945, and were unable to arrange for her journey to the United States and marriage until 1947. She died in 1987.

Leonard is survived by his wife, Peggy Phelps, of Pasadena; his daughter, Marcia, of Maplewood, New Jersey; his sons Kenneth, of Agoura Hills, James, of Olympia, Washington, and David, of Seattle, Washington; and seven grandchildren.

A memorial service is planned for 3 p.m. Monday, November 13, at All Saints Church, 132 North Euclid Avenue, Pasadena. Memorial donations should be made to the Nelson J. Leonard Fund at the Pasadena Symphony.

Robert Tindol

Caltech Chemist Jacqueline Barton Receives Gibbs Medal from American Chemical Society

PASADENA, Calif.—Jacqueline Barton, the Arthur and Marian Hanisch Memorial Professor and professor of chemistry at the California Institute of Technology, has been named the 2006 recipient of the Willard Gibbs Award. The honor was bestowed on Barton at a special award dinner hosted by the Chicago section of the American Chemical Society on May 12 in Des Plaines, Illinois.

Barton becomes the second woman to receive the honor in its 95-year history, the first having been Marie Curie in 1921. Barton and her husband, Peter Dervan (the Bren Professor of Chemistry at Caltech), also become the first husband and wife to have won the Gibbs Award.

Established in 1911, the Gibbs Award is presented annually to a researcher who pioneers new avenues of investigation in chemistry. Barton is cited for her "major impact on the understanding of the molecular chemistry of DNA and its relevance to the development of a variety of diseases and inherited abnormalities.

"Her work is elegant, vitally important work that has been widely recognized for its novelty and significance," the citation continues. "Professor Barton pioneered the application of transition metal complexes as tools to probe recognition and reactions of double helical DNA. This work provides a new approach to the study of DNA structure and dynamics. She has carried out important studies to examine the transport of electric charge through DNA, establishing reactions by which DNA can be damaged from a distance as well as how lesions in DNA can be repaired, locally or at distant sites on the DNA helix. Her work also provides the basis for sensitive diagnostic sensors for DNA."

A New York native, Barton earned her bachelor's degree, summa cum laude, at Barnard College in 1974 and her doctorate in inorganic chemistry at Columbia University in 1978. After several years on the faculty at Columbia, she joined the Caltech faculty in 1989.

She is the recipient of numerous awards, including a MacArthur Foundation Fellowship in 1991, the 1985 Alan T. Waterman Award of the National Science Foundation, which recognizes an outstanding young science or engineering researcher, and the 1988 American Chemical Society Award in Pure Chemistry. She was elected a fellow of the American Academy of Arts and Sciences in 1991, fellow of the American Philosophical Society in 2000, and in 2002 Barton was elected to the National Academy of Sciences.

Other American Chemical Society awards include the 1987 Eli Lilly Award in Biological Chemistry, the 1992 Garvan Medal, the 1997 Nichols Medal, and the 2003 Breslow Award. She has also received the Columbia University Medal of Excellence in 1992, the Mayor of New York's Award in Science and Technology in 1988, the Paul Karrer Gold Medal (University of Zurich) in 1996, and the Weizmann Woman & Science Award in 1998. She has received several honorary degrees, including last year a Doctor of Science from Yale University.

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Caltech Researchers Create New Proteins by Recombining the Pieces of Existing Proteins

PASADENA, Calif.—An ongoing challenge in biochemistry is getting a handle on protein folding-that is, the way that DNA sequences determine the unique structure and functions of proteins, which then act as "biology's workhorses." Gaining mastery over the construction of proteins will someday lead to breakthroughs in medicine and pharmaceuticals.

One method for studying the determinants of a protein's structure and function is to analyze numerous proteins with similar structure and function-a protein family-as a group. By studying families of natural proteins, researchers can tease out many of the fundamental interactions responsible for a given property.

A team of chemical engineers, chemists, and biochemists at the California Institute of Technology have now managed to create a large number of proteins that are very different in sequence yet retain similar structures. The scientists use computational tools to analyze protein structures and pinpoint locations at which they can break them apart and then reassemble them, like Lego pieces. Each new construction is a protein with new functions and new potential enzyme actions.

Reporting in the April 10 issue of the Public Library of Science Biology, Caltech graduate student Christopher Otey and his colleagues show that they have successfully taken three proteins from nature, broken them each into eight pieces, and successfully reconstructed the pieces to form many new proteins. According to Otey, the potential number of new proteins from just three proteins is three raised to the eighth power, or 6,561, assuming that each protein is divided into eight segments. "The result is an artificial protein family," Otey explains. "In this single experiment, we've been able to make about 3,000 new proteins."

About half of the 6,561 proteins are viable, having an average of about 72 sequence changes. "The benefit is that you can use the new proteins and new sequence information to learn new things about the original proteins," Otey adds. "For example, if a certain protein function depends on one amino acid that never changes, then the protein apparently must have that particular amino acid."

The proteins the team has been using are called cytochromes P450, which play critical roles in drug metabolism, hormone synthesis, and the biodegradation of many chemicals. Using computational techniques, the researchers predict how to break up this roughly 460-amino-acid protein into individual blocks of about 60 to 70 amino acids.

Otey says that this is an important result when considering the old-fashioned way of obtaining protein sequences. Whereas, over the past 40 years, researchers have fully determined 4,500 natural P450 sequences, the Caltech team required only a few months to create 3,000 additional new sequences.

"Our goal in the lab is to be able to create a bunch of proteins very quickly," Otey says, "but the overall benefit is an understanding of what makes a protein do what it does and potentially the production of new pharmaceuticals, new antibiotics, and such.

"During evolution, nature conserves protein structure, which we do with the computational tools, while changing protein sequence which can lead to proteins with new functions," he says. "And new functions can ultimately result in new treatments."

In addition to Otey, the other authors of the paper are Frances Arnold (the corresponding author), who is Dickinson Professor of Chemical Engineering and Biochemistry at Caltech, and Otey's supervising professor; Marco Landwehr, a postdoctoral scholar in biochemistry; Jeffrey B. Endelman, a recently graduated Caltech graduate student in bioengineering; Jesse Bloom, a graduate student in chemistry; and Kaori Hiraga, a Caltech postdoctoral scholar who is now at the New York State Department of Health.

The title of the article is "Structure-Guided Recombination Creates an Artificial Family of Cytochromes P450."


Robert Tindol
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Watson Lecture: Revolutionary Medicine

PASADENA, Calif.- Imagine taking a medicine that is not only ideally suited for treating your particular ailment but also perfectly designed for YOU and your own unique genetic makeup.

Scientists are making great strides toward the creation of this new generation of personalized pharmaceuticals. On January 18, William A. Goddard III will discuss the progress that has been made and where it might lead in his talk "The Coming Revolution in Pharmaceuticals." Goddard is the Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics and director of the Materials and Process Simulation Center at the California Institute of Technology.

The talk, the final program of the 2005-06 Earnest C. Watson Lecture Series, will take place at 8 p.m. in Beckman Auditorium, 332 S. Michigan Avenue south of Del Mar Boulevard, on the Caltech campus in Pasadena. Seating is available on a free, no-ticket-required, first-come, first-served basis. Caltech has offered the Watson Lecture Series since 1922, when it was conceived by the late Caltech physicist Earnest Watson as a way to explain science to the local community.

For more information, call 1(888) 2CALTECH (1-888-222-5832) or (626) 395-4652. ###

Contact: Kathy Svitil (626) 395-8022 ksvitil@caltech.edu

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Caltech Researchers Achieve First Electrowetting of Carbon Nanotubes

PASADENA, Calif.—If you can imagine the straw in your soda can being a million times smaller and made of carbon, you pretty much have a mental picture of a carbon nanotube. Scientists have been making them at will for years, but have never gotten the nanotubes to suck up liquid metal to form tiny wires. In fact, conventional wisdom and hundreds of refereed papers say that such is not even possible.

Now, with the aid of an 1875 study of mercury's electrical properties, researchers from the California Institute of Technology have succeeded in forcing liquid mercury into carbon nanotubes. Their technique could have important applications, including nanolithography, the production of nanowires with unique quantum properties, nano-sized plumbing for the transport of extremely small fluid quantities, and electronic circuitry many times smaller than the smallest in existence today.

Reporting in the December 2 issue of the journal Science, Caltech assistant professor of chemistry Patrick Collier and associate professor of chemical engineering Konstantinos Giapis describe their success in electrowetting carbon nanotubes. By "electrowetting" they mean that the voltage applied to a nanotube immersed in mercury causes the liquid metal to rise into the nanotube by capillary action and cling to the surface of its inner wall.

Besides its potential for fundamental research and commercial applications, Giapis says that the result is an opportunity to set the record straight. "We have found that when measuring the properties of carbon nanotubes in contact with liquid metals, researchers need to take into account that the application of a voltage can result in electrically activated wetting of the nanotube.

"Ever since carbon nanotubes were discovered in 1991, people have envisioned using them as molds to make nanowires or as nanochannels for flowing liquids. The hope was to have the nanotubes act like molecular straws," says Giapis.

However, researchers never got liquid metal to flow into the straws, and eventually dismissed the possibility that metal could even do so because of surface tension. Mercury was considered totally unpromising because, as anyone knows who has played with liquid mercury in chemistry class, a glob will roll around a desktop without wetting anything it touches.

"The consensus was that the surface tension of metals was just too high to wet the walls of the nanotubes," adds Collier, the co-lead author of the paper. This is not to say that researchers have never been able to force anything into a nanotube: in fact, they have, albeit by using more complex and less controllable ways that have always led to the formation of discontinuous wires.

Collier and Giapis enter the picture because they had been experimenting with coating nanotubes with an insulator in order to create tiny probes for future medical and industrial applications. In attaching nanotubes to gold-coated atomic force microscope tips to form nanoprobes, they discovered that the setup provided a novel way of making liquid mercury rise in the tubes by capillary action.

Casting far beyond the nanotube research papers of the last decade, the researchers found an 1875 study by Nobel Prize-winning physicist Gabriel Lippmann that described in detail how the surface tension of mercury is altered by the application of an electrical potential. Lippmann's 1875 paper provided the starting point for Collier and Giapis to begin their electrowetting experiments.

After mercury entered the nanotubes with the application of a voltage, the researchers further discovered that the mercury rapidly escaped from the nanotubes immediately after the voltage was turned off. "This effect made it very difficult to provide hard proof that electrowetting occurred," Collier said. In the end, persistence and hard work paid off as the results in the Science paper demonstrate.

Giapis and Collier think that they will be able to drive various other metals into the nanotubes by employing the process at higher temperature. They hope to be able to freeze the metal nanowires in the nanotubes so that they remain intact when the voltage is turned off.

"We can pump mercury at this point, but it's possible that you could also pump nonmetallic liquids," Giapis says. "So we now have a way of pumping fluids controllably that could lead to nanofluidic devices. We envision making nano-inkjet printers that will use metal ink to print text and circuitry with nanometer precision. These devices could be scaled up to operate in a massively parallel manner. "

The paper is titled "Electrowetting in Carbon Nanotubes." In addition to Collier and Giapis, the other authors are Jinyu Chen, a postdoctoral scholar in chemistry, and Aleksandr Kutana, a postdoctoral scholar in chemical engineering.

Robert Tindol
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