The Book of Bruck

The 2008 Winner of Caltech's Top Teaching Prize Talks About the Art and Science of Sharing Information

How would Jehoshua "Shuki" Bruck sum up his success as a teacher in just three words? "I love ignorance," declares the exuberant winner of Caltech's 2008 Feynman Prize for Excellence in Teaching.  

Shuki, as everyone calls him, is Caltech's Gordon and Betty Moore Professor of Computation and Neural Systems and Electrical Engineering. The Feynman Prize citation praised him for his "development of a new course, IST [Information Science and Technology] 4, 'Information and Logic,' as well as other teaching activities, including informal mentoring of undergraduates." An avalanche of recommendations commented on the breadth, humor, warmth, openness, and originality he brings to his teaching and on the special quality of his relationship with students. No one mentioned ignorance.

Shuki first taught IST4 in 2007, and he credits Caltech's interdisciplinary environment with sparking his interest in the subject not long after he arrived on campus in 1994. He played a leading role in conceiving and establishing Caltech's IST program, which culminated this October in the opening of the new Walter and Leonore Annenberg Center for Information Science and Technology.  Heidi Aspaturian of Caltech's communications office recently sat down with Shuki to get a firsthand idea of what it takes to be deemed a great teacher at Caltech.

Many people who nominated you for the Feynman Prize described IST4 as one of the best courses, if not the best, that they had taken at Caltech. What can you tell us about it?

SB: I first started thinking about this topic many years ago. Caltech turns out to be the perfect environment for thinking broadly about information science because we have so few disciplinary boundaries. Since I first came here, I have been very lucky to interact with people across all our divisions, from biology to physics to the humanities. And that helped me to realize that the topic of information systems encompasses far more than just computers. The cell, the brain, the Internet, and national and global economies are all information systems. What they all have in common is that information flows in and some manifestation of it flows out.

At the same time I realized that the biggest challenge in trying to understand all these different systems is that we don't have a good language—good mathematical tools, if you will—for dealing with them. We are collecting huge amounts of information, and we not only don't know what to do with all of it, we are also missing a good unifying framework for thinking about it. And yet that hasn't stopped us from being able to design, build, program, and use complex systems like tiny computer chips with one billion components to solve extremely difficult computations. How are we able to do it?

That question led me to a much larger one, namely, how did we get here from there?  How did we, as humans, get from having no conscious concept of numbers to a point where we are suddenly awash in all this advanced computational technology? What were the key milestones in this evolution? Classes about information science don't really deal with these questions. They focus on what's happened over the last 50 years or so, when that is really only a small part of a much bigger picture.

So I started reading and the more I read, the more questions I had. And you know, one of the best ways for a professor to learn more about a topic is to teach it. That's when I designed and started teaching this course. Three years later, I have to say, I still feel ignorant about the subject. But I love ignorance. It's something I truly love about my job—how to enjoy ignorance, and how to turn that feeling of ignorance into high energy and curiosity that I can then share and pass on to my students.

How do you go about relishing ignorance in this particular class?

SB: I begin with what you might call the puzzle of our innate sense for quantities. How is it, for example, that when we look at two piles of apples, we somehow know that one pile contains more fruit than the other?  Without knowing about the actual numbers themselves, we can still make this determination. There is a whole research area in cognitive science regarding number sense and the discovery that many animals—rats, crows, dogs, and so forth—have at least a rudimentary quantitative understanding. We now know that babies, long before they can talk, are able to relate to quantities and are pretty good at adding small numbers. So the first problem sets relate to these questions.

From there we look at early civilizations, starting with the Babylonians, who were amazingly sophisticated with numbers and numerical calculations. Among many other things, they invented base 60, which still serves as the basis for how we tell time. In computation, they had a wonderful representation that is actually a combination of base 60 and the binary system.

So we start with anthropology and ancient cultures, and even as we move into the Age of Enlightenment and the dawn of computational science in the 17th century, I try to retain this context. Eventually we reach the 20th century and the birth of modern computational approaches and computer technologies.

It is an evolving process, and I am always adding and experimenting with new material. Last year, I introduced material about language, specifically literacy versus illiteracy, and how that affects our thinking and our perceptions. We talked about some very interesting research related to how the ability to read and write shapes the way we perceive the world, and we tried to connect that aspect to the development of mathematics as our language for reasoning about the physical world. When I teach the class in '10, I am planning to bring in the whole notion of how creativity works. We'll talk about some famous innovators who developed ideas that are completely out of the intellectual mainstream and we'll explore how that occurred.

When your students encounter this rather unorthodox blend of hard science, mathematics, and intellectual history, how do they react?

SB: Some students really like it. Some just tolerate it. There are others who say, okay, just show us how we got computers and let us work on computational techniques—who cares about the Babylonians?  In some sense this relates to the whole philosophy-of-education question—whether it is more important to teach content or context. As I said earlier, I think we need to teach both. I will sometimes say to my students: This class is useless in the sense that you cannot take it and go get a job in a high-tech company and do something useful. This is not the idea. The idea is to teach you about the context in which ideas evolve, to amplify your curiosity, and to help you understand the dynamics of creativity and problem solving in a global sense over time. That's what I'm trying to convey.

 How would you describe your overall philosophy of teaching? Or do you have one?

SB: I'll tell you a story. When my son was in second grade, he asked me about something mathematical, I think involving addition. I was trying to explain to him the idea and afterward, he said, "Dad, when you were explaining this, you were smiling all the time. Why?" And I said, "It's because I like this stuff." And you see, that's a key thing that we need to teach. We are teaching "the smile."  We as teachers need to show the students that it's fun to understand the ideas that we present. This is how you amplify interest and curiosity. And you cannot cheat on that, right?  If it's not fun, who will want do it?

Feat of Clay: This tablet, dating back to at least 1,600 BCE, depicts Babylonian mathematical calculations in the civilization's cuneiform script.
Credit: Yale University Collection

But I think that the most important thing we do is actually shown on the Caltech logo, where you see the flame, the torch, and the two hands. The two hands aren't holding the torch together; one hand is passing it to the other. And this is something that is key to civilization. It is like DNA, but it is intellectual DNA—passing down the light of knowledge. To do that, it's not enough to teach and learn the mechanics of how to solve a quadratic equation. If you want to deepen understanding, you need to talk about the context in which the ideas you're teaching evolved.

I always try to emphasize that solving a problem or coming up with new ideas is a process, and that as students become accustomed to this approach, they should feel joyful in accomplishing it.  When I give them their early homework sets, I will tell them that certain problems will probably not be difficult—they are directly related to what we have studied in class. However, they will also find that other problems are not so straightforward, that they require more thinking. I tell them, "At first, you won't have any idea how to approach it. That's wonderful—that's the feeling you should have. Go and have fun. Go play music, go to the gym, go and see a movie. When you come back, take a look at it again, and the next morning you will have some idea, and you need to let yourself go through that."

Nearly every letter about you to the Feynman Prize Committee commented on the strong personal interest that you take in your students' welfare, both in and beyond the classroom. Do you think this attitude comes naturally to you, or did it develop out of years of teaching?

SB: What I think it comes down to is that I really like people. It's very hard to teach people unless you also have a sense of how they think and feel and where they are emotionally. I believe that classroom teaching is just a small part of our job. In the end what the students remember about the coursework is not the key. The key is that hopefully I am serving as a good model for them with regard to how to behave in a position like this—how to teach and how to relate to other people. And I hope that I can give them an example of what I believe is a good value system. Sometimes my students will tell me, "You helped me so much, and I don't know how I can thank you properly."  I tell them it's very simple: just do the same thing when you are in my position.

You spent almost two years, in 2006–2008, living with your family among students as a professor-in-residence at Avery House. What impact did that have on your teaching?

SB: I think it made me a better teacher, particularly of undergraduates. In my first years here, I taught mainly graduate classes, and my interaction with undergraduates was limited. I don't think I was able to "read" what they were saying all that well. Living in Avery, I began to feel that I could understand them much better. I suddenly became much more knowledgeable about the challenges of being an undergrad here.

What would you say are the top three challenges?

SB: The students who come here are gifted in so many ways—it's unbelievable. But for many of them, it's their first time in a community where everyone else is just as talented. It can be disconcerting to discover this, and there are different ways to handle it. One way is to be extremely happy that now you too are ordinary. Personally I feel like an average guy here at Caltech, and it's a great feeling, because this is how I know I am at the right place. For some people, however, it's hard to deal with. My experience with the students here is that the happy ones are those who accept who they are, regardless of where they are academically. Even if you are the best student at Caltech, you still need to learn how to manage that. Don't be arrogant. Do develop a social system that is not based on academic achievements but on interpersonal relationships and emotions. It doesn't matter what your class ranking is. You need to accept it and forget about it, and treat yourself as a whole person.

The second challenge is that when someone is the best student in their school, or their city, or maybe even in their state, then that is "their" movie. You know the saying that everyone lives in some kind of a movie?  That's their role—best student in New York. Then they come to Caltech. Now they are just one of the undergrads at Caltech. They are not even the best student in their student house. So suddenly it's a different movie and they need to adjust to their new role. That's a positive challenge, in my opinion.

The third challenge is that when these students are in high school, they are so talented that they can do very well without actually having to go into much depth about the material they are studying. It's not so easy to skate by that way here, and learning how to delve deeply into subjects or ideas doesn't just happen overnight. It's a matter partly of talent and partly of curiosity. And I think the main challenge for us as teachers is to make sure that curiosity flourishes.

If young colleagues just starting out asked you for advice on how to be a successful teacher, what would you tell them?

SB: Let me just say first that I am not sure I am a successful teacher. This award was a huge honor, but an even bigger surprise. Over the years I have started to feel more confident about teaching, but I still have a long way to go.

But I think that the key is really to love the material. It all starts with that and continues with a constant effort to discover new possibilities in the material and new ways to explain it, first to yourself, and then to others. That is how you pass on the light to the next generation. And you have to be willing to take risks. It's never clear when you set out to explain something whether the approach you've chosen is going to work. It might work well in your mind but then not so well in practice. It might work with one audience but fall flat with another. I have to say that I am naturally nervous about my teaching. I might not appear that way, but I put a huge amount of time and thought into preparing for my classes and I am always very anxious before a class. I have some story line that's all over the place in my brain and I'm trying to get it out in a lucid way. You have to be willing to experiment, to listen to feedback from your students, and to accept the fact that not everything you try is going to succeed.

What's most important, I think, is to reach into whatever your passion is and try to express it, explain it, and if it doesn't work well the first time, then try again.

And, again, I think the connection with the students is really why we do this job. Even if all that my students learn is how I treat them in class and how I respond to questions, that's a valuable lesson about information. It may be the most valuable one I can teach.

So that would be my suggestion to young people who aspire to teach: try to connect with your students because, in the end, whatever they get from you, you will get so much more from them. And I should also mention something that strikes me each year as I look at a new class for the first time: your students help keep you young. We get a bit older every year, but our undergraduates—they stay forever the same age.

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Heidi Aspaturian
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Caltech Scientists Find Emotion-like Behaviors, Regulated by Dopamine, in Fruit Flies

Finding may provide new insights into the neurological basis of ADHD, learning deficits, and more

PASADENA, Calif.—Scientists at the California Institute of Technology (Caltech) have uncovered evidence of a primitive emotion-like behavior in the fruit fly, Drosophila melanogaster.

Their findings, which may be relevant to the relationship between the neurotransmitter dopamine and attention deficit hyperactivity disorder (ADHD), are described in the December issue of the journal Neuron.

The Drosophila brain contains only about 20,000 neurons and has long been considered a powerful system with which to study the genetic basis of behaviors such as learning and courtship, as well as memory and circadian rhythms. What hasn't been clear is whether the Drosophila brain also could be used to study the genetic basis of "emotional" behaviors.

"Such studies are important," says David Anderson, Caltech's Seymour Benzer Professor of Biology and a Howard Hughes Medical Institute investigator, "because it's believed that abnormalities in these types of behaviors may underlie many psychiatric disorders."

Most of the genes found in the fruit fly—more accurately referred to as the vinegar fly—are found in humans as well, including those neurons that produce brain chemicals like dopamine and serotonin, which have been implicated in psychiatric disorders.

In their Neuron paper, the Caltech team—led by postdoctoral fellow Tim Lebestky—found that a series of brief but brisk air puffs, delivered in rapid succession, caused flies to run around their test chamber in what Anderson calls a "frantic manner." This behavior persisted for several minutes after the last of the puffs.

"Even after the flies had 'calmed down,'" he adds, "they remained hypersensitive to a single air puff."

To quantify the flies' behavior, Anderson's group collaborated with Pietro Perona, the Allen E. Puckett Professor of Electrical Engineering at Caltech. Together with his students, Perona developed an automated machine-vision-based system to track the movement of the flies, and derived a simple mathematical model to fit the movement data and to extract metrics that described various aspects of the flies' responses under different conditions.

The researchers used this test to search for flies with an abnormally exaggerated hyperactivity response; genetic studies of these flies revealed that a mutation in a dopamine receptor (a mutation that eliminates the receptor) produced the aberrant behavior. Flies with this dopamine-receptor mutation were hypersensitive to the air puffs, and took much longer to calm down than did "normal" flies without the mutation.

What is surprising about this result, notes Lebestky, “is that previous studies in both flies and vertebrates had suggested that dopamine promotes activity, but our experiments uncovered a function of dopamine in the opposite direction."  Because removing the receptor causes hypersensitivity to the air puffs, these results “suggested that dopamine actively inhibits the hyperactivity response,” Lebestky says.

This observation suggested a possible link to ADHD, a behavioral disorder characterized by impulsivity, hyperactivity, and short attention span. Humans with the disorder often take drugs, such as Ritalin, that increase levels of brain dopamine in order to reduce hyperactivity.

The ways the mutant flies respond to the air puffs is, moreover, "reminiscent of the way in which individuals with ADHD display hypersensitivity to environmental stimuli and are more easily aroused by such influences," says Anderson. Importantly, ADHD has been genetically linked to abnormalities of the dopamine system in humans, further strengthening the analogy between the mutant flies and this psychiatric disorder.

There is also another possible link: some individuals with ADHD display learning disabilities. Similarly, researchers from Pennsylvania State University—who collaborated on the Neuron study—have shown previously that flies with the same dopamine receptor mutation are unable to learn to associate a particular odor with an electric shock, and do not avoid the odor when subsequently tested. (Flies without the mutation quickly learn to make the association.)

It is often assumed that because individuals with ADHD are hyperactive and easily distracted, they have difficulty learning. The Caltech group showed, however, that hyperactivity and learning disabilities are not causally related in flies bearing the dopamine receptor mutation, thereby disproving the theory—at least in flies.

"We could separately 'rescue' the hyperactivity and learning deficits in a completely independent manner," says Anderson, "by genetically restoring the dopamine receptor to different regions of the fly's brain."

Thus, in dopamine-receptor-mutant flies, hyperactivity does not seem to cause learning deficits. Instead, these two "symptoms" reflect independent effects of the mutation that manifest themselves in distinct brain regions. "Being able to observe and manipulate the different neural substrates for learning and arousal will hopefully give us a unique method for identifying new molecular pathways that could be investigated and validated in higher organisms," says Lebestky.

This finding in flies, notes Anderson, raises the possibility that hyperactivity and learning deficits also may not be causally linked in humans with ADHD. If so, he says, it ultimately may prove more effective to develop drugs to treat these two symptoms separately, rather than trying to cure them both with the broad-spectrum pharmaceuticals currently available, which have many undesirable side effects.

"The finding that flies exhibit emotion-like behaviors that are controlled by some of the same brain chemicals as in humans opens up the possibility of applying the powerful genetics of this 'model organism' to understanding how these chemicals influence behavior through their actions on specific brain circuits," says Anderson. "While the specific details of where and how this occurs are likely to be different in flies and in humans, the basic principles are likely to be evolutionarily conserved, and may aid in our understanding of what goes wrong in disorders such as ADHD."

In addition to Lebestky, Anderson, and Perona, other researchers on the Neuron paper, "Two Different Forms of Arousal in Drosophila are Oppositely Regulated by the Dopamine D1 Receptor Ortholog DopR via Distinct Neural Circuits," are Jung-Sook Chang, Heiko Dankert, and Lihi Zelnik from Caltech; Young-Cho Kim and Kyung-An Han from Pennsylvania State University; and Fred Wolf from the University of California, San Francisco. Their work was funded by grants from the National Science Foundation and the Howard Hughes Medical Institute.

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Lori Oliwenstein
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Caltech and Dow Chemical Team Up in Solar Materials Effort

Collaboration includes the creation of Dow Graduate Fellowship in Chemical Sciences and Engineering

PASADENA, Calif.—The California Institute of Technology (Caltech) and the Dow Chemical Company today announced a new solar-research collaboration aimed at developing the use of semiconductor materials that are less expensive and more abundant than those used in many of today's solar cells.

In addition, they announced the creation of the Dow Chemical Company Graduate Fellowship in Chemical Sciences and Engineering.

The fellowship will be granted to a second- or third-year doctoral student who shows excellence in research, leadership, and interpersonal effectiveness, and whose research program aligns with broad areas of interest to Dow, such as alternative energy sources, the development of novel specialty chemicals, and the investigation of new polymer systems. Dow's $500,000 gift will be matched by $250,000 in funds from the Gordon and Betty Moore Matching Program.

Each recipient will be selected by the chair of the Division of Chemistry and Chemical Engineering, and will hold the fellowship for up to two years.

"We are pleased that Dow and Caltech are building this relationship to support innovative research as a basis for new technologies," says Jacqueline K. Barton, the division's current chair.

The solar-research collaboration will be a four-year, $4.2 million effort to explore earth-abundant materials for solar-energy applications. The project is led by applied physicist Harry Atwater, Caltech's Howard Hughes Professor, and chemist Nate Lewis, Caltech's George L. Argyros Professor.

"In combining the R&D strengths of Dow and Caltech, we have created a powerful alliance for innovation in the field of photovoltaics," says Bill Banholzer, executive vice president and chief technology officer of Dow. "This alliance will allow the best scientists the opportunity to work together to achieve the kinds of breakthrough technologies that will be game-changing in solar-energy capture."

The new Dow/Caltech solar-research initiative is one of the company's largest externally funded research agreements, Banholzer notes.

As part of the agreement, Atwater, Lewis, and their team will develop new mineral-like electronic materials suitable for use in thin-film solar-energy-conversion devices. 

"Development of materials that are abundant in the earth's crust will enable solar-energy technologies to ultimately scale to large volumes at low cost without concern about the materials' availability," says Atwater.

Most solar cells today are made with silicon, which is itself an abundant material. Still, silicon solar technology has a relatively higher cost than that of current thin-film solar materials like cadmium telluride and copper indium diselenide. But these inexpensive semiconductors pose a problem of their own: they contain materials too scarce to ultimately meet the demands of full-scale solar-energy technologies.

That's why Atwater and Lewis are turning their attention to semiconductors found in the earth's crust.

"Use of earth-abundant materials can provide new technology options and could open new areas of design space," Lewis notes. "But it also brings new challenges. This project will develop the science and technology base for thin-film solar-energy conversion using these widely available materials."

"This is an example of industry stepping up to the plate with a long-term vision that acknowledges the importance of supporting research in its most fundamental forms," says Ares Rosakis, chair of the Division of Engineering and Applied Science at Caltech and Theodore von Kármán Professor of Aeronautics and Mechanical Engineering.

"Dow understands that high-quality research is occurring in both industrial and academic laboratories. We believe that partnerships like this one are crucial to our success in the development of efficient, affordable energy solutions," says Banholzer.

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Lori Oliwenstein
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Caltech Scientists Develop DNA Origami Nanoscale Breadboards for Carbon Nanotube Circuits

PASADENA, Calif.—In work that someday may lead to the development of novel types of nanoscale electronic devices, an interdisciplinary team of researchers at the California Institute of Technology (Caltech) has combined DNA's talent for self-assembly with the remarkable electronic properties of carbon nanotubes, thereby suggesting a solution to the long-standing problem of organizing carbon nanotubes into nanoscale electronic circuits.

A paper about the work appeared November 8 in the early online edition of Nature Nanotechnology

"This project is one of those great 'Where else but at Caltech?' stories," says Erik Winfree, associate professor of computer science, computation and neural systems, and bioengineering at Caltech, and one of four faculty members supervising the project.

Both the initial idea for the project and its eventual execution came from three students: Hareem T. Maune, a graduate student studying carbon nanotube physics in the laboratory of Marc Bockrath (then Caltech assistant professor of applied physics, now at the University of California, Riverside); Si-ping Han, a theorist in materials science, investigating the interactions between carbon nanotubes and DNA in the Caltech laboratory of William A. Goddard III, Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics; and Robert D. Barish, an undergraduate majoring in computer science who was working on complex DNA self-assembly in Winfree's lab.

The project began in 2005, shortly after Paul W. K. Rothemund invented his revolutionary DNA origami technique. At the time, Rothemund was a postdoctoral scholar in Winfree's laboratory; today, he is a senior research associate in bioengineering, computer science, and computation and neural systems.

Rothemund's work gave Maune, Han, and Barish the idea to use DNA origami to build carbon nanotube circuits. 

DNA origami is a type of self-assembled structure made from DNA that can be programmed to form nearly limitless shapes and patterns (such as smiley faces or maps of the Western Hemisphere or even electrical diagrams). Exploiting the sequence-recognition properties of DNA base pairing, DNA origami are created from a long single strand of viral DNA and a mixture of different short synthetic DNA strands that bind to and "staple" the viral DNA into the desired shape, typically about 100 nanometers (nm) on a side.

Single-wall carbon nanotubes are molecular tubes composed of rolled-up hexagonal mesh of carbon atoms. With diameters measuring less than 2 nm and yet with lengths of many microns, they have a reputation as some of the strongest, most heat-conductive, and most electronically interesting materials that are known. For years, researchers have been trying to harness their unique properties in nanoscale devices, but precisely arranging them into desirable geometric patterns has been a major stumbling block. 

"After hearing Paul's talk, Hareem got excited about the idea of putting nanotubes on origami," Winfree recalls. "Meanwhile, Rob had been talking to his friend Si-ping, and they independently had become excited about the same idea."

Underlying the students' excitement was the hope that DNA origami could be used as 100 nm by 100 nm molecular breadboards—construction bases for prototyping electronic circuits—on which researchers could build sophisticated devices simply by designing the sequences in the origami so that specific nanotubes would attach in preassigned positions. 

"Before talking with these students," Winfree continues, "I had zero interest in working with carbon nanotubes or applying our lab's DNA-engineering expertise toward such practical ends. But, seemingly out of nowhere, a team had self-assembled with a remarkable spectrum of skills and a lot of enthusiasm. Even Si-Ping, a consummate theorist, went into the lab to help make the idea become reality."

"This collaborative research project is evidence of how we at Caltech select the top students in science and engineering and place them in an environment where their creativity and imagination can thrive," says Ares Rosakis, chair of the Division of Engineering and Applied Science at Caltech and Theodore von Kármán Professor of Aeronautics and Professor of Mechanical Engineering.

Bringing the students' ideas to fruition wasn't easy. "Carbon nanotube chemistry is notoriously difficult and messy—the things are entirely carbon, after all, so it's extremely difficult to make a reaction happen at one chosen carbon atom and not at all the others," Winfree explains.

"This difficulty with chemically grabbing a nanotube at a well-defined 'handle' is the essence of the problem when you're trying to place nanotubes where you want them so you can build complex devices and circuits," he says.

The scientists' ingenious solution was to exploit the stickiness of single-stranded DNA to create those missing handles. It's this stickiness that unites the two strands that make up a DNA helix, through the pairing of DNA's nucleotide bases (A, T, C, and G) with those that have complementary sequences (A with T, C with G). 

"DNA is the perfect molecule for recognizing other strands of DNA, and single-stranded DNA also just happens to like sticking to carbon nanotubes," says Han, "so we mix bare nanotubes with DNA molecules in salt water, and they stick all over the nanotubes' surfaces. However, we make sure that a little bit of each DNA molecule is protected, so that that little portion doesn't stick to the nanotube, and we can use it to recognize DNA attached to the DNA origami instead."

The scientists created two batches of carbon nanotubes labeled by DNA with different sequences, which they called "red" and "blue."

"Metaphorically, we dipped one batch of nanotubes in red DNA paint, and dipped another batch of nanotubes in blue DNA paint," Winfree says. Remarkably, this DNA paint acts like color-specific Velcro.

"These DNA molecules served as handles because a pair of single-stranded DNA molecules with complementary sequences will wrap around each other to form a double helix. Thus," he says, "'red' can bind strongly to 'anti-red,' and 'blue' with 'anti-blue.'"

"Consequently," he adds, "if we draw a stripe of anti-red DNA on a surface, and pour the red-coated nanotubes over it, the nanotubes will stick on the line. But the blue-coated nanotubes won't stick, because they only stick to an anti-blue line."

To make nanometer-scale electronic circuits out of carbon nanotubes requires the ability to draw nanometer-scale stripes of DNA. Previously, this would have been an impossible task.

Rothemund's invention of DNA origami, however, made it possible.

"A standard DNA origami is a rectangle about 100 nm in size, with over 200 'pixel' positions where arbitrary DNA strands can be attached," Winfree says. To integrate the carbon nanotubes into this system, the scientists colored some of those pixels anti-red, and others anti-blue, effectively marking the positions where they wanted the color-matched nanotubes to stick. They then designed the origami so that the red-labeled nanotubes would cross perpendicular to the blue nanotubes, making what is known as a field-effect transistor (FET), one of the most basic devices for building semiconductor circuits.

Although their process is conceptually simple, the researchers had to work out many kinks, such as separating the bundles of carbon nanotubes into individual molecules and attaching the single-stranded DNA; finding the right protection for these DNA strands so they remained able to recognize their partners on the origami; and finding the right chemical conditions for self-assembly.

After about a year, the team had successfully placed crossed nanotubes on the origami; they were able to see the crossing via atomic force microscopy. These systems were removed from solution and placed on a surface, after which leads were attached to measure the device's electrical properties. When the team's simple device was wired up to electrodes, it indeed behaved like a field-effect transistor.  The "field effect" is useful because "the two components of the transistor, the channel and the gate, don't actually have to touch for there to be a switching effect," Rothemund explains. "One carbon nanotube can switch the conductivity of the other due only to the electric field that forms when a voltage is applied to it."

At this point, the researchers were confident that they had created a method that could construct a device from a mixture of nanotubes and origami.

"It worked," Winfree says. "I can't say perfectly—there's lots of room for improvement. But it was sufficient to demonstrate the controlled construction of a simple device, a cross-junction of a pair of carbon nanotubes."

"We expect that our approach can be improved and extended to reliably construct more complex circuits involving carbon nanotubes and perhaps other elements including electrodes and wiring," Goddard says, "which we anticipate will provide new ways to probe the behavior and properties of these remarkable molecules."

The real benefit of the approach, he points out, is that self-assembly doesn't just make one device at a time. "This is a scalable technology. That is, one can design the origami to construct complex logic units, and to do this for thousands or millions or billions of units that self-assemble in parallel."

The work in the paper, "Self-assembly of carbon nanotubes into two-dimensional geometries using DNA origami templates," was supported by the National Science Foundation, the Office of Naval Research, and the Center on Functional Engineered Nano Architectonics.

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Kathy Svitil
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James. K. Knowles, 78

James K. Knowles, William J. Keenan Jr. Professor of Applied Mechanics, Emeritus, at the California Institute of Technology (Caltech), passed away November 1. He was 78 years old.

Knowles made fundamental research contributions to the theory of nonlinear elasticity and the mathematical theories of materials and structures.

His work provided important insight into how various materials and structures behave and enabled him and others to develop predictive theories.

Born in Cleveland, Ohio, on April 14, 1931, Knowles grew up in Phoenix, Arizona. He entered the Massachusetts Institute of Technology (MIT) in the fall of 1948, earning his bachelor's and doctoral degrees, both in mathematics, in 1952 and 1957, respectively. He then stayed at MIT for an additional year, as an instructor in mathematics.

Knowles joined the faculty at Caltech in 1958 as assistant professor of applied mechanics; he was named associate professor in 1961, followed by full professor in 1965. He spent the remainder of his academic career at Caltech, becoming professor emeritus in 1997.

Considered a remarkable teacher and mentor, Knowles inspired and influenced generations of students and scholars through classes in mathematics and mechanics. A visionary thinker, he recruited and mentored a number of junior colleagues who took Caltech in new and fruitful research directions. He had a deep affection for Caltech and served in various administrative capacities.

"Jim was the greatest mentor I ever had. He held my hand when I first came to Caltech as an assistant professor. He also taught me how to teach," says Ares Rosakis, chair of the Division of Engineering and Applied Science, and Theodore von Kármán Professor of Aeronautics and Mechanical Engineering at Caltech. "He would look for the spark in people's eyes and help them make their dreams a reality. As we at Caltech seek to create the best mentoring opportunities for our young faculty, we should be guided by Jim's example."

Knowles' research was primarily focused on mathematical problems in structural mechanics, and in particular on linear and nonlinear elasticity. In 1960, he provided the first solution for a dynamical problem in finite elasticity and in 1966, he published what would turn out to be a seminal paper concerning the foundations of Saint-Venant's principle in linear elasticity theory.

His later papers on the influence of nonlinearity on point singularities, such as those found at the tip of a crack, demonstrated how they could lead to new phenomena.

In 1979, Knowles published a paper concerning the dissipation of mechanical energy during quasi-static motions of elastic bodies. This led to his later work on the evolution of metastable states of equilibrium, which had applications in phase transformations.

Knowles' contributions are described in more than one hundred journal publications. In 1998, he authored a textbook for graduate students entitled Linear Vector Spaces and Cartesian Tensors (Oxford University Press).

In 1991, he was made an honorary member of the Caltech Alumni Association in recognition of his distinguished service. That same year, the Journal of Elasticity dedicated an issue to Knowles on the occasion of his 60th birthday for "seminal contributions made to the field of elasticity."

"He set an example of scholarship and fundamental thought, both broad and deep, that challenged students as well as researchers," says Roger Fosdick, editor-in-chief of the Journal of Elasticity. "He was highly inquisitive, deeply thoughtful, masterfully insightful and always seeking an explanation. He made indelible marks of value during his life both personally and professionally, and he will most certainly be missed."

Knowles' contributions were also recognized by the Society of Engineering Science with the Eringen Medal, and by the American Society of Mechanical Engineers with the Koiter Medal.

Knowles was a fellow of the American Academy of Mechanics, the American Society of Mechanical Engineers, and the American Association for the Advancement of Science, and was associate editor for the Journal of Applied Mechanics. From 1985 to 1986, he served as president of the American Academy of Mechanics.

Knowles was known outside the classroom for his paintings and baritone voice.

He leaves behind a wife, Jacqueline, and sons John, Jeff, and James, and their families.

A graveside service is scheduled for Saturday, November 14, at 10:30 a.m. at Sierra Madre Pioneer Cemetery, 553 East Sierra Madre Boulevard (at the corner of Coburn Avenue and Sierra Madre Boulevard), in Sierra Madre.

The Division of Engineering and Applied Science has established a memorial fund in honor of Knowles. The fund will support the James K. Knowles Lecture in Solid Mechanics at Caltech, to be delivered annually by an internationally recognized scholar chosen by the faculty. The lecture will be followed by a workshop on solid mechanics, which will be a daylong event of talks by selected current Caltech graduate students and postdoctoral scholars in the area of solid mechanics. The Knowles lecture and workshop will commemorate Knowles' contributions to solid mechanics, his love for Caltech, and his encouragement of young researchers.

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Two Caltech Researchers Receive DARPA Young Faculty Awards

PASADENA, Calif.—The Defense Advanced Research Projects Agency (DARPA) has selected two researchers from the California Institute of Technology (Caltech) to participate in its Young Faculty Award (YFA) program.

Julia R. Greer, assistant professor of materials science, and Doris Tsao, assistant professor of biology, are among the 33 "rising stars" from 24 U.S. universities who each will receive grants of approximately $300,000 to develop and validate their research ideas over the next 24 months.

Greer joined the Caltech faculty in the Division of Engineering and Applied Science (EAS) in 2007 after receiving her PhD from Stanford University in 2005. In 2008, Greer made Technology Review's list of the world's top innovators under the age of 35 for her work with materials at the nanoscale level. In 2008, she received a Faculty Early Career Development award from the National Science Foundation.

Greer's YFA project is aimed at understanding and subsequently mimicking the superior mechanical robustness and strength of naturally occurring protective layers—such as nacre, or mother of pearl, a composite produced by some mollusks to line their inner shell—to create strong, ductile, damage-tolerant materials that maintain a relatively low density.

"Drawing inspiration from hard biological systems will allow us to gain insight into new physical phenomena operating in these materials, and to subsequently create innovative material systems with greatly amplified mechanical properties dictated by the choice of individual components, specific geometries, and microstructure in a truly across-scales fashion," says Greer.

One key objective of the work will be to fabricate a "brick-and-mortar" architecture using tiny plates of a metallic glass and ultrafine-grained ductile metal with nanoscale dimensions; this hierarchical architecture could then be used to fabricate new engineering composites with amplified strength and ductility.

"Greer's nature-inspired work exemplifies the cutting-edge research being carried out in the division," says Ares Rosakis, chair of EAS and Theodore von Kármán Professor of Aeronautics and Mechanical Engineering.

Tsao received her PhD from Harvard University in 2002, and came to Caltech in 2009 from the University of Bremen in Germany. She was named on Technology Review's 2007 list of top young innovators; in 2009, she became a John Merck Scholar, a Searle Scholar, and a Klingenstein Scholar.

Tsao uses functional magnetic resonance imaging, electrical recordings from single neurons, anatomical measurements, and mathematical modeling to understand how the brain identifies objects and reconstructs the three-dimensional world. Specifically, her proposed work will attempt to decipher the neural machinery underlying spatial navigation. 

"Navigation, which is the purposeful movement through space guided by sensory feedback and memory, is a defining behavior in all animals," says Tsao. Understanding the brain mechanisms responsible for navigation, she says, "constitutes a critical step toward designing artificial systems capable of human-like autonomous navigation. Such systems may be used to explore dangerous terrain and to perform tasks, such as clearing land mines, that could risk the loss of human life."

The objective of the DARPA YFA program is to identify and engage rising research stars in junior faculty positions in academia.  The YFA program provides funding mentoring, and industry and Department of Defense (DOD) contacts to these faculty members early in their careers, so that they can develop their research ideas in the context of the needs of the DOD. DARPA's long-term goal for this program is to develop the next generation of academic scientists, engineers, and mathematicians in key disciplines who will focus a significant portion of their careers on DOD and National Security issues.

The YFA awardees were chosen though a competitive selection process. Applicants were required to be untenured faculty at U.S. institutions within six years of appointment to a tenure-track position. Nearly 300 proposals were reviewed for the 2009 awards.

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Caltech Scientists First to Trap Light and Sound Vibrations Together in Nanocrystal

Optomechanical crystals could be used in information processing, as supersensitive biosensors, and more

PASADENA, Calif.—Researchers at the California Institute of Technology (Caltech) have created a nanoscale crystal device that, for the first time, allows scientists to confine both light and sound vibrations in the same tiny space.

"This is a whole new concept," notes Oskar Painter, associate professor of applied physics at Caltech. Painter is the principal investigator on the paper describing the work, which was published in the online edition of the journal Nature. "People have known how to manipulate light, and they've known how to manipulate sound. But they hadn't realized that we can manipulate both at the same time, and that the waves will interact very strongly within this single structure."

Indeed, Painter points out, the interactions between sound and light in this device—dubbed an optomechanical crystal—can result in mechanical vibrations with frequencies as high as tens of gigahertz, or 10 billion cycles per second. Being able to achieve such frequencies, he explains, gives these devices the ability to send large amounts of information, and opens up a wide array of potential applications—everything from lightwave communication systems to biosensors capable of detecting (or weighing) a single macromolecule. It could also, Painter says, be used as a research tool by scientists studying nanomechanics. "These structures would give a mass sensitivity that would rival conventional nanoelectromechanical systems because light in these structures is more sensitive to motion than a conventional electrical system is."

"And all of this," he adds, "can be done on a silicon microchip."

Optomechanical crystals focus on the most basic units—or quanta—of light and sound. (These are called photons and phonons, respectively.) As Painter notes, there has been a rich history of research into both photonic and phononic crystals, which use tiny energy traps called bandgaps to capture quanta of light or sound within their structures.

What hadn't been done before was to put those two types of crystals together and see what they are capable of doing. That is what the Caltech team has done.

"We now have the ability to manipulate sound and light in the same nanoplatform, and are able to interconvert energy between the two systems," says Painter. "And we can engineer these in nearly limitless ways."

The volume in which the light and sound are simultaneously confined is more than 100,000 times smaller than that of a human cell, notes Caltech graduate student Matt Eichenfield, the paper's first author. "This does two things," he says. "First, the interactions of the light and sound get stronger as the volume to which they are confined decreases. Second, the amount of mass that has to move to create the sound wave gets smaller as the volume decreases. We made the volume in which the light and sound live so small that the mass that vibrates to make the sound is about ten times less than a trillionth of a gram."

Eichenfield points out that, in addition to measuring high-frequency sound waves, the team demonstrated that it's actually possible to produce these waves using only light. "We can now convert light waves into microwave-frequency sound waves on the surface of a silicon microchip," he says.

These sound waves, he adds, are analogous to the light waves of a laser. "The way we have designed the system makes it possible to use these sound waves by routing them around on the chip, and making them interact with other on-chip systems. And, of course, we can then detect all these interactions again by using the light. Essentially, optomechanical crystals provide a whole new on-chip architecture in which light can generate, interact with, and detect high-frequency sound waves."

These optomechanical crystals were created as an offshoot of previous work done by Painter and colleagues on a nanoscale "zipper cavity," in which the mechanical properties of light and its interactions with motion were strengthened and enhanced. (That release can be found at http://media.caltech.edu/press_releases/13263.)

Like the zipper cavity, optomechanical crystals trap light; the difference is that the crystals trap—and intensify—sound waves, as well. Similarly, while the zipper cavities worked by funneling the light into the gap between two nanobeams—allowing the researchers to detect the beams' motion relative to one another—optomechanical crystals work on an even tinier scale, trapping both light and sound within a single nanobeam.

"Here we can actually see very small vibrations of sound trapped well inside a single 'string,' using the light trapped inside that string," says Eichenfield. "Importantly, although the method of sensing the motion is very different, we didn't lose the exquisite sensitivity to motion that the zipper had. We were able to keep the sensitivity to motion high while making another huge leap down in mass."

"As a technology, optomechanical crystals provide a platform on which to create planar circuits of sound and light," says Kerry Vahala, the Ted and Ginger Jenkins Professor of Information Science and Technology and professor of applied physics, and coauthor on the Nature paper. "These circuits can include an array of functions for generation, detection, and control. Moreover," he says, "optomechanical crystal structures are fabricated using materials and tools that are similar to those found in the semiconductor and photonics industries. Collectively, this means that phonons have joined photons and electrons as possible ways to manipulate and process information on a chip."

And these information-processing possibilities are well within reach, notes Painter. "It's not one plus one equals two, but one plus one equals ten in terms of what you can do with these things. All of these applications are much closer than they were before."

"This novel approach to bringing both light and sound together and letting them play off of each other exemplifies the forward-thinking work being done by the Engineering and Applied Science (EAS) division," says Ares Rosakis, chair of EAS and Theodore von Kármán Professor of Aeronautics and Mechanical Engineering at Caltech.

Other authors on the Nature paper, "Optomechanical crystals," include Caltech graduate student Jasper Chan and postdoctoral scholar Ryan Camacho. Funding for their work was provided by a Defense Advanced Research Projects Agency seed grant and by grants from the National Science Foundation.

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Caltech Scientists Solve Decade-Long Mystery of Nanopillar Formations

Research paves way for new 3-D lithography method

Pasadena, Calif.—Scientists at the California Institute of Technology (Caltech) have uncovered the physical mechanism by which arrays of nanoscale (billionths-of-a-meter) pillars can be grown on polymer films with very high precision, in potentially limitless patterns.

This nanofluidic process—developed by Sandra Troian, professor of applied physics, aeronautics, and mechanical engineering at Caltech, and described in a recent article in the journal Physical Review Letters—could someday replace conventional lithographic patterning techniques now used to build three-dimensional nano- and microscale structures for use in optical, photonic, and biofluidic devices.

The fabrication of high-resolution, large-area nanoarrays relies heavily on conventional photolithographic patterning techniques, which involve treatments using ultraviolet light and harsh chemicals that alternately dissolve and etch silicon wafers and other materials. Photolithography is used to fabricate integrated circuits and microelectromechanical devices, for example.

However, the repeated cycles of dissolution and etching cause a significant amount of surface roughness in the nanostructures, ultimately limiting their performance.

"This process is also inherently two-dimensional, and thus three-dimensional structures must be patterned layer by layer," says Troian.

In an effort to reduce cost, processing time, and roughness, researchers have been exploring alternative techniques whereby molten films can be patterned and solidified in situ, and in a single step.

About a decade ago, groups in Germany, China, and the United States encountered a bizarre phenomenon while using techniques involving thermal gradients. When molten polymer nanofilms were inserted within a slender gap separating two silicon wafers that were held at different temperatures, arrays of nanoscale pillars spontaneously developed.

These protrusions grew until they reached the top wafer; the resulting pillars were typically several hundred nanometers high and several microns apart.

These pillars sometimes merged, forming patterns that looked like bicycle chains when viewed from above; in other films, the pillars grew in evenly spaced, honeycomb-like arrays. Once the system was brought back down to room temperature, the structures solidified in place to produce self-organized features.

In 2002, researchers in Germany who had observed this phenomenon hypothesized that the pillars arise from infinitesimal—but very real—pressure fluctuations along the surface of an otherwise quiescent flat film. They proposed that the differences in surface pressure were caused by equally tiny variations in the way individual packets (or quanta) of vibrational energy, known as phonons, reflect from the film interfaces.

"In their model, the difference in acoustic impedance between the air and polymer is believed to generate an imbalance in phonon flux that causes a radiation pressure that destabilizes the film, allowing pillar formation," says Troian. "Their mechanism is the acoustic analogue of the Casimir force, which is quite familiar to physicists working at the nanoscale."

But Troian, who was familiar with thermal effects at small scales—and knew that the propagation of these phonons is actually unlikely in amorphous polymer melts, which lack internal periodic structure—immediately recognized that another mechanism might be lurking in this system.

To determine the actual cause of nanopillar formation, she and Caltech postdoctoral scholar Mathias Dietzel developed a fluid-dynamical model of the same type of thin, molten nanofilm in a thermal gradient.

Their model, Troian says, "exhibited a self-organizing instability that was able to reproduce the strange formations," and showed that nanopillars, in fact, form not via pressure fluctuations but through a simple physical process known as thermocapillary flow.

In capillary flow—or capillary action—the attractive force, or cohesion, between molecules of the same liquid (say, water) produces surface tension, the compressive force that is responsible for holding together a droplet of water. Since surface tension tends to minimize the surface area of a liquid, it often acts as a stabilizing mechanism against deformation caused by other forces. Differences in temperature along a liquid interface, however, generate differences in surface tension. In most liquids, cooler regions will have a higher surface tension than warmer ones—and this imbalance can cause the liquid to flow from warmer- to cooler-temperature regions, a process known as thermocapillary flow.

Previously, Troian has used such forces for microfluidic applications, to move droplets from one point to another.

"You can see this effect very nicely if you move an ice cube in a figure eight beneath a metal sheet coated with a liquid like glycerol," she says. "The liquid wells up above the cube as it traces out the figure. You can draw your name in this way, and, presto! You have got yourself a new form of thermocapillary lithography!"

In their Physical Review Letters paper, Troian and Dietzel showed how this effect can theoretically dominate all other forces at nanoscale dimensions, and also showed that the phenomenon is not peculiar to polymer films.

In the thermal-gradient experiments, they say, the tips of the tiny protrusions in the polymer film experience a slightly colder temperature than the surrounding liquid, because of their proximity to the cooler wafer.

"The surface tension at an evolving tip is just a little bit greater, and this sets up a very strong force oriented parallel to the air/polymer interface, which bootstraps the fluid toward the cooler wafer. The closer the tip gets to the wafer, the colder it becomes, leading to a self-reinforcing instability," Troian explains.

 

Upper: Schematic showing typical experimental setup. Lower: AFM image of 260 nm high nanopillars spaced 3.4 microns apart which formed in a polymer film.
Credit: Upper: Dietzel and Troian/Caltech; PRL. Lower: Chou and Zhuang, J. Vac. Sci. Technol. B 17, 3197 (1999).

Ultimately, she says, "you can end up with very long columnar structures. The only limit to the height of the column, or nanopillar, is the separation distance of the wafers."

In computer models, the researchers were able to use targeted variations in the temperature of the cooler substrate to control precisely the pattern replicated in the nanofilm. In one such model, they created a three-dimensional "nanorelief" of the Caltech logo.

Troian and her colleagues are now beginning experiments in the laboratory in which they hope to fabricate a diverse array of nanoscale optical and photonic elements. "We are shooting for nanostructures with specularly smooth surfaces—as smooth as you could ever make them—and 3-D shapes that are not easily attainable using conventional lithography," Troian says.

"This is an example of how basic understanding of the principles of physics and mechanics can lead to unexpected discoveries which may have far-reaching, practical implications," says Ares Rosakis, chair of the Division of Engineering and Applied Science (EAS) and Theodore von Kármán Professor of Aeronautics and Mechanical Engineering at Caltech. "This is the real strength of the EAS division."

The work in the paper, "Formation of Nanopillar Arrays in Ultrathin Viscous Films: The Critical Role of Thermocapillary Stresses," was funded by the Engineering Directorate of the National Science Foundation.

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Two International Leaders Receive Caltech Aerospace Award

Former president of India and France's top space administrator recognized for their achievements in the field

Pasadena, Calif., Sept. 15, 2009- Two distinguished aerospace leaders are the recipients of the 25th annual International von Kármán Wings Award. Receiving the honor this year are Abdul Kalam, the 11th president of India and distinguished professor at the Indian Institute of Technology, and Yannick d'Escatha, chairman and chief executive officer of the Centre National d'Etudes Spatiales (CNES), the agency responsible for shaping France's space policy.

"Along with their tremendous accomplishments in aerospace, this year's honorees are leaders in international collaboration, climate monitoring, and energy harvesting," says Ares J. Rosakis, chair of the Aerospace Historical Society, chair of the Division of Engineering and Applied Science, and Theodore von Kármán Professor of Aeronautics and Mechanical Engineering at Caltech.

This is the 25th year that the International von Kármán Wings Award has been given by the Aerospace Historical Society (AHS), which is now apart of the Graduate Aerospace Laboratories at Caltech (GALCIT). The award has a rich heritage in the preservation of world aerospace history and the recognition of renowned aerospace pioneers and luminaries.

"GALCIT is proud and privileged to be the home of the Aerospace Historical Society," says G. Ravi Ravichandran, director of the Graduate Aerospace Laboratories and the John E. Goode, Jr., Professor of Aeronautics and Mechanical Engineering. "It is an honor to give this award, named after the founding director of GALCIT and the founder of the Jet Propulsion Laboratory, to Abdul Kalam and Yannick d'Escatha."

Rosakis described Adbul Kalam as an "international leader and humanitarian who is honored and admired by the next generation" and Yannick d'Escatha as a "visionary who is using space and technology to bring about collaboration and peace."  

One example of the honorees' collaborative efforts is the Megha-Tropiques weather satellite, a joint project of the Indian Space Research Organization (ISRO) and the French Centre National d'Etudes Spatiales (CNES).

The von Kármán Wings Awards will be handed out September 15 at a banquet on the Caltech campus and will be presented by Rosakis.

Previous recipients of the Wings Award include last year's winner, Northrop Grumman's chief technology officer Alexis Livanos; director of the NASA Jet Propulsion Laboratory Charles Elachi; Kent Kresa, chairman of Caltech's Board of Trustees; TRW cofounder Simon Ramo; aerospace engineer Burt Rutan; and astronaut Buzz Aldrin.

About Abdul Kalam:

Abdul Kalam, the 11th president of India, was born in 1931 in Rameswaram, in the Indian state of Tamil Nadu. He attended the Madras Institute of Technology, specializing in aeronautical engineering. Dr. Kalam was the project director of India's first indigenous Satellite Launch Vehicle (SLV-III), which successfully propelled the Rohini satellite into near-Earth orbit in July 1980 and made India a member of the exclusive "space club."

After working for two decades in the Indian Space Research Organization (ISRO) and mastering launch vehicle technologies, Dr. Kalam took up the responsibility of developing indigenous guided missiles at the Defense Research and Development Organization as the chief executive of the Integrated Guided Missile Development Program. He was responsible for the development and operations of AGNI and PRITHVI missiles and for building indigenous capability in critical technologies through networking with multiple institutions. Dr. Kalam was the scientific advisor to India's defense minister and secretary and boosted the country's self-reliance in defense systems by advancing multiple mission projects, such as the Light Combat Aircraft.

Dr. Kalam became the 11th president of India in July 2002 and served for five years. He led the country in arriving at Technology Vision 2020, giving a road map for transforming India from its present developing status to a developed nation.

Dr. Kalam is a distinguished professor at the Indian Institute of Technology and has also authored a number of books, including Wings of Fire, India 2020:A Vision for the New Millennium and Ignited Minds: Unleashing the Power Within India. These books have been translated into many Indian and foreign languages.

Being one of the most distinguished scientists of India, Dr. Kalam has received honorary doctorates from 36 universities and institutions in India and abroad. The Royal Society of the United Kingdom has awarded to him the King Charles II Medal for Science and Technology.

About Yannick d'Escatha:

Yannick d'Escatha was born in 1948 in Paris, France. He graduated from École des Mines and École Polytechnique, where he became a professor and was the chairman of the board of trustees. He was internationally recognized for his research in solid, structural, and fracture mechanics.

In 1973, he became an expert advisor to the minister of industry on nuclear regulatory and research issues. D'Escatha was the administrator general of the French Atomic Energy Commission (CEA) and chairman of the CEA Industrie Group. At CEA, he promoted astrophysics and global-change research and concentrated on the spin-off potential of the R&D activities.

Ares Rosakis (left) and Abdul Kalam
Credit: Bob Paz

He served as chief operating officer and vice president of Électricité de France from 2000 to 2003.

In 2003, d'Escatha was appointed chairman and chief executive officer of the CNES. He conducted an ambitious policy to restructure the French space agency. In addition, he secured the Ariane 5 launcher system and recently issued a report on future launch systems to the French prime minister. At CNES, he developed research and applications dedicated to global change. He led the CNES Automated Transfer Vehicle (ATV) Control Center to successfully dock the European ATV with the International Space Station.

D'Escatha is an advocate for international space cooperation. He is responsible for creating large partnerships with the top spacefaring nations in Europe and with other international partners. In Europe, he provides leadership for the new European Space Policy by encouraging strong partnership between ESA and European Union institutions. He also provided the road map for the European Space Council during the French presidency of the European Union (2008).

D'Escatha received two distinguished awards from the Académie des Sciences. He is a member of the Académie des Technologies and served on a variety of French Applied Science and Technology Councils. The French Republic awarded him both the Commandeur de l'Ordre National du Mérite and the Officier de la Légion d'Honneur decorations.

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About GALCIT:

The research at the Graduate Aerospace Laboratories of the California Institute of Technology (GALCIT) has evolved over the past three-quarters of a century to include aerospace and biosystems engineering. However, the tradition of integrating basic experiments, theory, and simulations over a broad range of spatial and temporal scales continues to characterize its approach.

GALCIT faculty are highly visible in their fields and continue to garner numerous awards. GALCIT contains unparalleled experimental facilities in solids, fluids, biomechanics, propulsion, combustion, and materials, as well as unique large-scale computational capabilities.

Its educational emphasis is on the fundamentals and advanced diagnostics, with a view toward the future, of biomechanics, biopropulsion, micro and nanomechanics, space science, and space technology. GALCIT takes an interdisciplinary view of mechanics-fluids, solids, and materials-and its graduate training reflects this focus.

About Caltech:

Caltech is recognized for its highly select student body of 900 undergraduates and 1,200 graduate students, and for its outstanding faculty. Since 1923, Caltech faculty and alumni have garnered 32 Nobel Prizes and five Crafoord Prizes.

In addition to its prestigious on-campus research programs, Caltech operates the Jet Propulsion Laboratory (JPL), the W. M. Keck Observatory in Mauna Kea, the Palomar Observatory, and the Laser Interferometer Gravitational-Wave Observatory (LIGO). Caltech is a private university in Pasadena, California. For more information, visit http://www.caltech.edu.

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Caltech and IBM Scientists Use Self-Assembled DNA Scaffolding to Build Tiny Circuit Boards

Nanotechnology advance could lead to smaller, faster, more energy-efficient computer chips

Pasadena, Calif.--Scientists at the California Institute of Technology (Caltech) and IBM's Almaden Research Center have developed a new technique to orient and position self-assembled DNA shapes and patterns--or "DNA origami"--on surfaces that are compatible with today's semiconductor manufacturing equipment. These precisely positioned DNA nanostructures, each no more than one one-thousandth the width of a human hair, can serve as scaffolds or miniature circuit boards for the precise assembly of computer-chip components.

The advance, described in the current issue of the journal Nature Nanotechnology, could allow the semiconductor industry to pack more power and speed into tiny computer chips, while making them more energy efficient and less expensive to manufacture than is possible today.  

DNA origami structures have been heralded as a potential breakthrough for the creation of nanoscale circuits and devices. In a process created by Caltech senior research associate Paul W. K. Rothemund and his colleagues, DNA molecules self-assemble in solution via a reaction between a long single strand of viral DNA and a mixture of different short synthetic DNA strands. These short segments act as staples that effectively fold the viral DNA into desired two-dimensional shapes through complementary base-pair binding.

In this way, DNA nanostructures such as squares, triangles, and stars can be prepared that measure 100 to 150 nanometers on an edge and are as thick as the DNA double helix is wide. 

One roadblock to the use of DNA origami, however, is that the structures are made in saltwater solution--whereas electronic circuits are created on surfaces, like a silicon wafer, so they can be integrated with other technologies.

DNA origami structures also adhere randomly to surfaces, which means that "if you just pour DNA origami over a surface to which they stick, they attach everywhere," explains Rothemund, who jointly led the project with IBM. "It's a little like taking a deck of playing cards and throwing it on the floor; they are scattered willy-nilly all over the place. Such random arrangements of DNA origami are not very useful. If they carry electronic circuits, for example, they are difficult to find and wire up into larger circuits."  

To eliminate these problems, Rothemund and his colleagues at the Almaden Research Center developed a way to precisely position DNA origami nanostructures on a surface, "to line them up like little ducks in a row," Rothemund says. "This knocks down one of the major roadblocks for the use of DNA origami in technology," he adds.

In a process developed by IBM scientists, electron-beam lithography and oxygen plasma etching, conventional semiconductor techniques, are used to make patterns on silicon wafers, creating lithographic templates of the proper size and shape to match those of individual triangular DNA origami structures created by Rothemund. The etched patches are negatively charged, as are DNA origami structures, and are therefore "sticky."

To connect the origami to the templates, magnesium ions are added to the saltwater solution containing the origami. The positively charged magnesium ions can stick to both the DNA origami and the negatively charged patches on the template. Thus, when the solution is poured over the template, a negative-positive-negative "sandwich" is formed, with the magnesium atoms acting as a glue to hold the origami to the sticky patches.

"The triangles bind strongly to the sticky patches, but also they can wiggle a bit, so they line up with the outline of the sticky patch. So not only can we put origami where we want them, but they can be oriented in the direction we want them," Rothemund says.

The positioned DNA nanostructures can then serve as scaffolds or miniature circuit boards for the precise assembly of components such as carbon nanotubes, nanowires, and nanoparticles at dimensions significantly smaller than possible with conventional semiconductor fabrication techniques. This opens up the possibility of creating functional devices that can be integrated into larger structures as well as enabling studies of arrays of nanostructures with known coordinates.

"The spacing between the components can be 6 nanometers, so the resolution of the process is roughly 10 times higher than the process we currently use to make computer chips," Rothemund says. "Then, if you want to design a really small electronic device, say, you just design DNA strands to create the pattern you want, attach little chemical 'fastening posts' to those DNA strands, assemble the pattern, and then assemble the components onto the pattern," he explains.

The process isn't limited to organizing things that are of interest to physical scientists and engineers, like electronic components, Rothemund adds. For example, he says, "Biologists studying how proteins interact can place them in patterns on top of DNA origami. This may be useful in the case of motor proteins, the little machines that power our muscles. They work in gangs, with multiple motors pulling together. To study how different configurations of motors cooperate, scientists may use DNA origami to organize the gangs."

"Rothemund and his colleagues have removed a key barrier to the improvement and advancement of computer chips. They accomplished this through the revolutionary approach of combining the building blocks for life with the building blocks for computing," says Ares Rosakis, Theodore von Kármán Professor of Aeronautics and Mechanical Engineering and chair of Caltech's Division of Engineering and Applied Science.

The paper, "Placement and orientation of individual DNA shapes on lithographically patterned surfaces," was published in the August 16 issue of Nature Nanotechnology. The work was supported by the National Science Foundation and the Focus Center Research Program.

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