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Deborah Chung

Deborah D.L. Chung

Professor, Department of Mechanical and Aerospace Engineering,
School of Engineering and Applied Sciences, University at Buffalo, The State University of New York

By David Zierler, Director of the Caltech Heritage Project
March 7, 2023

DAVID ZIERLER: This is David Zierler, Director of the Caltech Heritage Project. It is Tuesday, March 7, 2023. I am delighted to be here with Professor Deborah Chung. Deborah, it's so nice to be with you. Thank you for joining me today.

DEBORAH CHUNG: Thank you so much for having me.

ZIERLER: To start, would you please tell me your title and affiliation?

CHUNG: I'm Professor at University at Buffalo, The State University of New York.

ZIERLER: What department are you in at Buffalo?

CHUNG: It's called Department of Mechanical and Aerospace Engineering. And I'm actually in materials science.

ZIERLER: That's your home discipline, you're a materials scientist?

CHUNG: Yes. That's what my PhD is in.

ZIERLER: Tell me about the kinds of things you work on. What is your research area?

CHUNG: One of the main areas is multifunctional structural materials. That is, structural material that's not only good as a structural material, having good mechanical properties, but at the same time, having some functional properties, such as sensing, energy generation, energy storage, vibration damping, electromagnetic shielding, and so on, so that the structure becomes multifunctional, like killing two birds with one stone. And I find very intriguing. It used to be an open area. I was the pioneer of this field. Because the field of structural materials has always been just the study of structural properties, mechanical properties, durability, that kind of thing. Nobody would think of studying the electrical properties of a structural material. It sounds crazy. [Laugh] Like studying the electrical properties of concrete. Are you crazy? [Laugh]

But I embarked on that kind of crazy direction of research, and that's how I got into multifunctional structural materials. They're really smart materials, but they're structural materials. And I find this to be a gold mine because people have not dealt with this at all, and it's very interdisciplinary because it involves both structural behavior and non-structural behavior. The non-structural behavior could be electrical, electromagnetic, optical, and so on. It's marrying two different areas that are traditionally totally separate. And that marriage enables me to make some contributions or impacts to the field.

ZIERLER: What were some of the technological or even theoretical advances that allowed for the field of multifunctional structural materials to come into existence?

CHUNG: There are two schools in this game. One school is, you embed in or attach to the surface a certain device, like a sensor, in the structure, incorporating that particular device. That's the easy route in terms of the science. You just buy something and embed it. What makes me very interested in it is that I don't go that route. Rather, I explore the inherent non-structural properties of a structural material in order to exploit that to enable the structural material, without the devices, to provide the non-structural function. And that involves real science, not just buying the device and embedding it. [Laugh] It's an area of science people have not thought about.

ZIERLER: What aspects of your research are purely basic science, and where are you motivated by specific applications?

CHUNG: Well, the observation of the non-structural properties of structural materials is brand new, and then, further, to understand that behavior in terms of the basic science that should follow. There are a number of non-structural properties, as I alluded to. For each type of non-structural property, you have different science that needs to be pulled in. Actually, the science has not been fully established. People are still mainly in the realm of experimentally observing the non-structural behavior.

ZIERLER: Tell me about your lab. What does it look like? What are the instruments that you use?

CHUNG: My lab involves preparation of materials as well as the testing or characterization of materials, whether it's carbon-fiber composite or concrete. One needs to make the stuff, and afterwards, one needs to test. And testing sounds easy. Actually, there are a lot of pitfalls. One of the reasons there are a lot of pitfalls is that researchers in structural materials are not really educated or trained in electrical measurements, for instance. They think, "Oh, it's easy. I use a meter, touch the sample with the two probes, and there I have the resistance." [Laugh] Actually, that's a pitfall because there's contact resistance at each contact. And that contact resistance can be very substantial so that you're not really measuring the specimen's resistance. When you subject the specimen to a force, the force might even affect the contacts more than the specimen, so you might be studying the contacts rather than the specimen. A lot of incorrect papers have been published because they measure the stuff incorrectly. This is one of the problems with interdisciplinary research. People want to get into a new area, but they don't really have the training for it, and they think it's easy, then they make a lot of mistakes, and a lot of flawed papers have been published.

ZIERLER: Have you ever been involved in startups or licensing these materials for industrial use?

CHUNG: Just to a minor degree. My major invention is smart concrete, what we also call self-sensing concrete. That is, concrete that is itself a sensor without having any sensor incorporated into it. I do have an issued US patent on that, quite some time ago. But I never got this licensed. One of the reasons is that the concrete industry is very archaic. It's the opposite of the electronic industry. Also, any new concrete would come with liability issues. If a bridge falls down, there will be a lawsuit. [Laugh] The industry is not conducive to using new concrete. Also, there's the bidding system. To build a bridge, you have to bid on it, and the lowest bidder would win. My modification of the concrete involves a price increase in the material, which is another hurdle. It's kind of sad that this licensing has not quite occurred.

ZIERLER: On the theoretical side, are there theories in mechanics or physics that provide intellectual guidelines for your experimental work?

CHUNG: The science also is interdisciplinary. The traditional science addresses the mechanical properties and the electrical properties of materials as two separate fields, two separate sets of theories. But one needs to marry the electrical and structural or mechanical theories together to form, say, an electromechanical theory, how the mechanical force impacts the electrical behavior. From the theoretical point of view, it's new in that respect.

ZIERLER: Have you served as a consultant to companies, or have you ever provided testimony in a policy setting?

CHUNG: I have served as an expert witness in quite a few lawsuits that involve companies suing one another for, say, patent infringement in various fields.

ZIERLER: Tell me about being a professor at Buffalo. What are some of the strengths and opportunities you have there?

CHUNG: Buffalo is like many other US research universities. It's nice to have the freedom to steer one's research. For instance, my department, as I told you, is called Mechanical and Aerospace Engineering, not Civil Engineering. But I do a lot of work on concrete, and the world out there often just assumes I'm in the Civil Engineering Department. But nobody complains in my department about my dealing with concrete research. [Laugh] That's just an example of the free rein one has in academia. That's why I wanted to go into academia.

ZIERLER: Do you do anything relevant to aerospace science?

CHUNG: Yes. I also study a lot about carbon fiber polymer composites, the type used for aircraft structures. And for this class of materials, just like for the concrete, one can get multifunctionality out of it. In fact, the science is very similar. I've done pretty much parallel research for this class of materials as well.

ZIERLER: Given your focus on cement, what have we learned so far? What is the best possible application of this science in creating the best possible forms of cement?

CHUNG: What I deal with is not creating a better cement in the sense of mechanical or functional properties. Rather, I want to bring out the non-structural functional abilities, an area people have not looked at. That is, I'm not necessarily making a new material, but I want to explore the non-structural properties of these existing structural materials. And actually, it's more impactful to investigate existing materials than new materials because existing structures, like bridges, involve existing materials, not new materials. If your research only uses the new materials and their multifunctionality, then your technology can only be applied to new structures, not existing structures. As a result, the applicability would be much narrower than the case of your technology being applicable to existing materials. In fact, that's something I don't like about how science is going on in this country because they always think, "Oh, is it a new material?" In fact, new materials that have a lot of complexity to them are called advanced materials, and journals and funding agencies will fund those advanced materials, exotic materials. But actually, if one doesn't use those exotic materials, but rather conventional, existing materials, and can provide the same or even better functional properties, that's even better. [Laugh] But they don't care about that.

ZIERLER: Now, in creating self-sensing concrete, might that be useful for earthquake mitigation?

CHUNG: It would be because the sensing can be not just the damage, but the stress as well. Even before an earthquake, the stress in the ground would be increased. One can use the concrete as a sensor to sense both the stress and the minor damage. The minor damage is very important because you would know ahead of time that something bad was going to happen, then you could repair the thing in a timely fashion. But the sensing these days is essentially all involving major damage. For instance, they use acoustics emission. That is, when something breaks, some sound comes out. And they hear the sound and say, "Oh, it's breaking." [Laugh] But that's major damage. What I provide is the ability to detect even very minor damage.

ZIERLER: What have been some of the advances in 3D printing technology that have been relevant for your research?

CHUNG: I have researched 3D printing as well. One problem of 3D printing pertains to the defects, particularly the very subtle defects between the printed layers. Those are more subtle than the voids within a printed layer. That is, local separation between the printed layers. This problem is particularly severe for metal printing because metal printing involves much higher temperatures than polymer printing. The high temperature results in a lot of thermal stress. You have one layer, and it's solidified and cooled, then you put the other layer on, which is very hot. You have a lot of thermal stress because the bottom has already finished contracting, and you're putting the top layer on, and it's trying to contract. There's a lot of thermal stress. As a result, for metal printing in particular, the inter-layer defects are very common. Warping of the metal structure is very common because of the abundance of inter-layer defects resulting from the high thermal stress. One needs to be able to sense those defects.

For instance, if you can sense the defects while the printing is occurring, you can perhaps adjust the printing conditions during the printing so that the layers afterwards would be better. This is called smart manufacturing. I've been dealing with the sensing of the defects, again, using some electrical methods, which turn out to be very sensitive and low-cost compared to what they are mainly using. For instance, they're mainly using cameras. The cameras look down from the top, and the inter-layer defects are hidden by the layer above. You can't see the inter-layer defects using cameras. Even though the 3D industry is growing tremendously, the commercial side of it is the main activity. The science space has not advanced very much. The problems with defects have remained all these years.

ZIERLER: What are some of the applications for which advances in vibration dampening are so important?

CHUNG: We don't want any structure to shake around. High-rise buildings, bridges, high-speed rails, even satellites. Shaking can cause problems for all of these things. Practically any structure wants to not shake, not vibrate. One of the common ways people try to alleviate this vibration problem is to use rubber or a similar polymer. And rubber has long molecules, and upon vibration, there's deformation involved. It's dynamic deformation and vibration, but it's deformation. As deformation occurs, the rubber will deform, and the molecules in it will move, so it soaks up some mechanical energy. Dissipating mechanical energy is what vibration damping means. Rubber or similar polymers are dominant in vibration damping. The problem is, the rubber is soft. The more you put into the structure, the weaker the structure is mechanically. And the mechanical performance of a structure is something you don't want to compromise, but by putting in the rubber, you are compromising it. That's the hurdle.

But what I have put forth is something kind of crazy. I exploit the stiff structural material to provide damping, which people have not even dreamed about. They always think rubber. "How can something stiff dampen?" In fact, I first reported this in 1998, and people just could not believe me. They think that if you improve the damping, the mechanical property has to go down. One up, one down, has to be the case. But I told them, "I get both damping and stiffness increased." [Laugh] But I involve a totally different science from what they know about. My science involves using the interfaces in the material. Upon vibration, there's very slight slippage at the interface. Not damage, just very slight slippage. And there's friction involved in the sliding. As a result, mechanical energy is consumed. If your material is nanostructured, so that you have lots of these interfaces, then this interface mechanism can be substantial in providing the damping. I called this new type of damping method interface-derived viscoelasticity. I coined that term. [Laugh] The nice thing about it is that the interfaces, if properly selected, can actually stiffen the material in addition to providing the damping. That's why using this new route, interface-derived viscoelasticity, it's possible to increase both damping and stiffness at the same time.

ZIERLER: Where do we see a need for microelectronic cooling?

CHUNG: Oh, the overheating of computers is the number-one headache in the electronic industry, computers getting too hot. How to cool microelectronics is a very, very big issue. The main route is to use a heat sink. A heat sink is a thermal conductor, and you let the microprocessor's heat go through the heat sink, and the heat sink directs the heat into the environment. That makes a lot of sense. However, there's a problem that people have not worried too much about, and that's the interface between the heat source and the heat sink. If that thermal contact is lousy, however wonderful your heat sink is, the heat is not able to get from the heat source to the heat sink, and you're just wasting the goodness of the heat sink. People put into that interface a material called a thermal interface material to improve that thermal interface, so there's less thermal resistance associated with that thermal interface.

They have been developing these thermal interface materials with the thought that the higher the thermal conductivity of that interface material is, the better the effectiveness. They've been developing thermal interface materials with the idea of maximizing the thermal conductivity. For instance, they would use an organic-based thermal paste, but they fill it with silver particles. Silver is a wonderful thermal conductor. By putting a lot of silver particles in, they get a paste that provides good thermal conductivity for use as a thermal interface material. The problem is, again, something they've overlooked. A very simple thought, but they've overlooked it in the electronics industry. What they've overlooked is that the thermal conductivity is not necessarily the primary criterium that determines the effectiveness of the thermal interface material.

An equally or even more important criterium is the ability of that thermal interface material to fill the microscopic valleys in that interface. That is, however you mechanically polish a surface, it's never going to be perfectly smooth. You have hills and valleys. When you have two surfaces touching, they're actually only touching at points. Between the points are just air voids. The interface material better displace all the air out and occupy those air voids. As long as the thermal conductivity is higher than air, it helps already. But in the electronic industry, they put in as many silver particles as possible, and the more silver particles they put in, the worse the conformability. But I figured out the importance of conformability, so I developed thermal paste that excels not because of the high thermal conductivity, but because of the high conformability. That's another area that's close to my heart.

ZIERLER: I wonder if you could explain the kinds of materials that need to have shielding from electromagnetic interference. What are those materials or technologies?

CHUNG: Computers can go crazy because of radio-frequency waves hitting them. Because those waves interact with the electrons. The flow of electrons being affected is obviously bad for computers. Not only for computers, but pacemakers. The pacemaker involves an electrical lead from the battery to the tip of the heart, and there's a current pulse that causes the heart to beat. One pulse, one beat. And if the electrons don't flow correctly, the heart doesn't beat. The patient would be in big, big trouble. And we have these radio-frequency waves all over the place. Fluorescent lamps, microwave ovens, cellular phones, fax machines, transformers. Almost all electronics emit radio-frequency waves. Our electronics are getting very sensitive. The need for protecting the electronics as well as making the radio wave not come out of the radiation source, such as the cell phone, both require what we call shielding materials. This need is growing very fast.

And shielding, again, is an interdisciplinary field. Shielding means you block the electromagnetic radiation so that it doesn't get through that shield. It involves reflection as well as absorption of the radiation, both of which prevent the radiation from getting through. That field traditionally resides in electrical engineering because they deal with electromagnetic radiation. But they're not trained in materials science. To develop the shielding materials, you need to design the materials with the understanding of how the radiation interacts with the material in terms of reflection as well as absorption. Electrical engineers tend to shy away from the developing of shielding materials. It's kind of not their cup of tea. The materials scientists also shy away from this because they think this electrical stuff is not their cup of tea. I find that middle ground my cup of tea, and it's very rewarding to study this interaction and to develop materials that are really good for the shielding.

ZIERLER: You've written about the road to scientific success. Beyond your own field, what have you learned about scientific success? What are some of the big lessons from your career in achieving success in science?

CHUNG: In science, one needs to impact it in the form of transformative progress, not just incremental progress. Say, you tweak something, and the strength increases by 5%. That's incremental. As an academic researcher, I'm not so interested in incremental improvement. I would be more excited about something that transforms the field because of the new science and new direction of thinking. For that to happen, one needs to be creative. Being creative means thinking about or realizing something before others do so that you lead the crowd. Nowadays, most researchers don't quite do that. They usually just read papers. "Ah, this paper looks good. I'll just follow this and keep going." That's a follower approach, which is okay, but I would be more excited to be a leader rather than a follower.

But in order to be a leader, one has to be creative. And to be creative, the ability to cross disciplinary boundaries, to jump out of one's comfort zone, is super important. If one's entire career of a few decades is only restricted to one's comfort zone, one particular discipline, one can make a lot of impact within that discipline, but the chance of creating something brand new is less than if that person is willing to cross the disciplinary boundary, to jump out of one's comfort zone. And to have the guts to jump out, one needs to have kind of a broad background in one's scientific training. In addition, one needs to be willing to keep learning. And pretty much everything I talked about today is due to my learning. [Laugh] I just learn as I go along. For instance, I've never mixed cement before. Broad learning as well as the guts to jump out, I think, are critical for creativity, which in turn is critical for making a substantial impact to science. In this regard, I must say that my education at Caltech was very good in providing me with that broad, basic foundation on which to build. And that's so crucial.

ZIERLER: That's a perfect segue. Why don't we now go back in history and learn about how you got to Caltech? First, tell me about where you were in high school and what your interests were at that point.

CHUNG: I got very interested in science toward the last few years of high school. Toward the end of my high school days, in 1969, the first man landed on the moon. I was in Hong Kong watching on TV. I was super excited because not only could a person walk on the moon, he could speak, and we could hear him speak. [Laugh] It was just tremendous. At that point, I told my parents, "I want to go to America to study aerospace engineering." And I actually went. Not so much into aerospace engineering because I didn't know what it was, but science. I went from Hong Kong to America all by myself to enter college. In those days, people were not as affluent as today. Parents would not accompany those international students to their new home, set up their beds, and so on. Nowadays, they do that, but not in those days. [Laugh]

ZIERLER: I understand you have a record of accomplishment, especially women in your family, of professional success.

CHUNG: Oh, yes. I'm very thankful that I have my mother as well as others I can talk about in my life who gave me wonderful examples and wonderful guidance, especially as I grew up. My mother, Rebecca, was a US World War II veteran with the Flying Tigers, which later became the US Army. That was in China during World War II. She worked under the famous General Chennault. She was a nurse. Later, she joined the work of flying over the Hump, which is the Himalayas. At that time, flying over the Hump was the only way for people to get in or out of China, because Japan had already locked up the eastern seaboard of China. And medical supplies in particular needed to go to China, so they had to fly them in. But it was just propeller planes, no computers. Propeller planes are not supposed to fly that high, and you have strong downward winds as you come down the slope.

The downward wind would push the aircraft down, so there were lots and lots of crashes. And the wreckages are still lying there on the slopes of the Himalayas today. My mother flew over the Hump as a nurse about 50 times. She was awarded, after her passing, the Congressional Gold Medal. Not only that, she was a very devout Christian, and in fact, her faith in God was very much a part of her ability to face all these difficulties during the War. I really thank God for having her in my life. And her mother was one of the first female doctors of Western Medicine in China. Western Medicine is not Chinese. [Laugh] China has its own medicine. But really, it's the medical missionaries from abroad who brought Western Medicine to China. My maternal grandmother went to a medical school that was founded by American medical missionaries. She became a physician. A lot of history in my family. [Laugh] I could go on and on.

ZIERLER: When you were in high school, how did you learn that Caltech, in 1970, had taken on this important decision to admit women undergraduates?

CHUNG: Actually, I'm not sure how I learned about it. I was actually a transfer student. I entered Caltech in 1971. I transferred from Wellesley College, where I studied in my freshman year. I'm not sure exactly how I learned about it, but I did have high school friends or classmates studying at Caltech at that time.

ZIERLER: What were your reasons for transferring? Did you want a more technical education than what Wellesley could provide?

CHUNG: Exactly. Wellesley is excellent in liberal arts education. But I didn't realize that that meant less science and math until I got there. In my freshman year, I was already taking senior-level mathematics courses, and I figured out there wasn't a whole lot left for me to study in terms of science or math. Because of that, I decided to transfer out of Wellesley.

ZIERLER: Tell me about when you first arrived in Pasadena on the Caltech campus. What were your early impressions?

CHUNG: Obviously, the weather is nice. [Laugh] But I really liked the friendliness, the personal touch at Caltech. Even though I was very much a minority as a girl there, I didn't feel special or abnormal at all. I just behaved the same way as all the other guys, and I didn't feel any discomfort. Actually, whether one gets discomfort or not depends on how one thinks. I just refused to feel abnormal. Whatever other people think is their business. I just behaved and studied like everybody else. It was not a problem at all in that environment for me.

ZIERLER: Did it feel like a brand-new decision that Caltech had admitted women? In other words, by the time you arrived in 1971, did it feel normal for undergraduate women to be there, or was it still very much in flux, according to your perspective?

CHUNG: Well, I felt normal. I didn't hear of some girls getting very upset and wanting to leave. I never heard that. Definitely not in flux. It seemed that people were okay. All those girls seemed okay, to me at least.

ZIERLER: What was the social situation like according to what house you lived in, who your friends were, how many were guys, how many were girls? How did that look to you?

CHUNG: I lived in Lloyd House. Obviously, they were all boys, just a few girls there. As you know, there are a lot of crazy traditional fun things that people at Caltech do, like throwing pies, throwing mud, or whatever. [Laugh] That was certainly new to me. But I accepted that. Even though it was kind of crazy, it was part of the fun environment and the show of friendship. Just like during finals, they would broadcast music early in the morning. [Laugh] You might think it's crazy, but it's kind of fun. I think I enjoyed the environment there, even socially.

ZIERLER: Coming from Wellesley, did you feel well-prepared to jump into the Caltech curriculum and all of its demands?

CHUNG: Yes, I had no problem. When I was in high school in Hong Kong, I went to perhaps the top high school for science in Hong Kong. It's called King's College. It's not a college, but a high school. [Laugh] Also, in general, the high school science and math curriculum in Hong Kong, at least in those days, were higher-level than those in America. The high schools in Hong Kong were very demanding. I had that advantage. And that's why in Wellesley, even in my freshman year, I was able to take senior-level math courses. Getting into Caltech, I didn't feel a whole lot of difficulty.

ZIERLER: What course of study did you settle on at Caltech?

CHUNG: Engineering. In particular, I kind of focused on electrical engineering. Part of the reason was that I was intrigued by integrated circuits. At that time, they were a new thing. I remember taking courses from Professor Carver Mead, who is perhaps the father of integrated circuits. I was fortunate to be in that famous little class that he gave, which taught us how to design and make integrated circuits. That was in 1972, very early. A lot of other universities were still teaching vacuum tubes, let apart transistors. At Caltech, we were teaching not only transistors, but integrated circuits. [Laugh] That's a very good example of the kind of cutting-edge education that Caltech provides. One often thinks of cutting-edge research and not cutting-edge education, but Caltech provides both, and I think that's beautiful.

ZIERLER: What did you do for the summers? Did you stay on campus, go back home?

CHUNG: I stayed pretty much on campus. I never went back home for months at a time, just limited stays. Another very nice thing about Caltech is that even for undergraduates, we could do research and get paid for it. Instead of flipping hamburgers, you could actually do research and get paid hourly. I had such a job, and that helped my finances tremendously.

ZIERLER: Where did you work?

CHUNG: I worked in the laboratory of Professor Pol Duwez, the father of amorphous metals. In fact, it was that research that got me hooked up to materials science. I told you that I was very much interested in electrical engineering, but it was through this research and Professor Duwez that I came to realize how much science as well as technology is embodied in materials science. After that research, I decided to go for graduate school in materials science. It's actually a big change because I changed my major from undergraduate to graduate school. And again, the broad education at Caltech enabled me to make such a change.

ZIERLER: Did anybody make a big deal of the fact that Caltech went coed? Do you recall anybody in the administration giving a speech, anything in the newspaper heralding this as a big decision?

CHUNG: I wasn't there when they made the decision, but I was there when I graduated. [Laugh] It was during graduation that I realized that they were making it kind of a big deal, and that was good. During my days at Caltech, before graduation, everything was normal, and that was good. But at graduation, we started to be in the limelight. [Laugh] Photographs were taken, and we ended up in newspapers, on the front of Caltech's engineering magazine, and all that. Then, I found out that our graduation picture is in the Caltech archive. If I go to the Caltech webpage and type Deborah Chung, my picture will come up. [Laugh] That's kind of fun. I'm thankful that I happened to be one of the first four women graduates of Caltech. It wasn't by design, it just happened like that.

ZIERLER: This was 1973 when you graduated because you were a transfer student. When you say you were there for your own graduation, being among those four women, during the ceremony, did anybody note that you were the first four? Was that made public? Or you just realized yourself that it was a big deal?

CHUNG: Before the ceremony, we had all that photography already done. Also, on the day with all the cap and gown also. Before that, without the cap and gown, the photography had already begun. During the ceremony, I don't think they announced it, but I think people knew.

ZIERLER: By the time you graduated, what were your options? What did you want to do next?

CHUNG: I clearly wanted to go to graduate school, get a PhD degree, and become a professor. And a lot of that had to do with my wish to do research that was totally free. In industry, you can also do research, but it's not as free. That's why I wanted to go into academia. Getting a PhD obviously is necessary for that.

ZIERLER: What kind of advice did you get about professors to work with, programs to apply to?

CHUNG: I don't think I got specific advice as to which schools to apply to for graduate school, so I just picked mostly the top schools to apply to. MIT was in the mix, so I went there.

ZIERLER: Did you know about Millie Dresselhaus, the famous carbon queen, when you were an undergraduate? Did her reputation precede her?

CHUNG: No, I did not know her at all until I went to MIT and took her class. And that class really hooked me to solid-state physics and graphite. That was how I chose her as my advisor, and I kept studying graphite or carbon.

ZIERLER: Tell me about when you got to MIT, how you developed a relationship with Millie.

CHUNG: Millie was very gracious and was very close to her graduate students. Not only did we have weekly group meetings, but I basically saw her every day, just to touch base. [Laugh] And I happened to play the piano, and she played the violin, and her family played string instruments. That was another common interest, which helped a little.

ZIERLER: How important was it for you to have a woman graduate advisor? I'm sure at Caltech, there were no women professors to work with.

CHUNG: That's probably true. I didn't notice any women professors when I was at Caltech. I chose Millie not because of the fact that she was female, but just because I liked her class. [Laugh] I liked the physics that she taught. Her gender was not part of my consideration at all.

ZIERLER: What was Millie working on when you first connected with her?

CHUNG: She was working on graphite. And she used the graphite as an illustration in the solid-state physics she taught in the class. Then, gradually, both she and I broadened our interests away from graphite to, say, carbon fiber. And for me, also carbon fiber composites. Also, carbon fiber cement. I broadened it bit by bit, but starting with the ideal graphite that I learned under her.

ZIERLER: I wonder how you see a transition from graphite to carbon fiber in Millie's work and then yours. How did that work?

CHUNG: Well, the carbon nanotube is an important springboard. The carbon nanotube is not carbon fiber in the strict sense, but it's fibrous. And the fullerene, some people got a Nobel Prize on that, and that evolved into carbon nanotube, and that got Millie very, very interested. But carbon fiber has been around for decades. The nanotube was what was new. Even for carbon fiber, there's a lot of basic science that has not been addressed. And there's similarity in the science. Whether graphite, carbon fiber, carbon nanotube, or graphene, there's a lot of similarity in the science. From the application point of view, carbon fiber is outstandingly important.

ZIERLER: What was Millie like as a person? What was it like to work with her, both in the lab and beyond?

CHUNG: She was extraordinarily gracious. She never said anything harsh or that would make you feel bad. Never. Always kind, always gracious. Even if one broke something in the lab, as I did, she did not complain. Because she understood the difficulty I faced in the lab. I was transferring liquid helium all by myself in the lab. Transferring liquid helium was not an easy task. It took a lot of muscle to do that, particularly in that particular lab, the National Magnet Lab, and I was doing it all by myself. During one of the transfers, something kind of tilted a little bit. [Laugh] And she could have been very upset, but she wasn't. She understood my difficulty.

ZIERLER: What were some of the main research questions that propelled your thesis research? What were you asking, what were you looking for?

CHUNG: My thesis under Millie was on graphite intercalation compounds. Graphite is a layered material with carbon layers, and one can expose the graphite to certain strong chemicals, which can go in between the layers as single atomic or molecular layers. And we call that process intercalation. The intercalation involves the transfer of electrons between what has gone in and the host carbon. It's really doping, just like doping a semiconductor. As a result, the concentration of mobile electrons is much increased, and the conductivity is much increased. And Millie was very interested in that effect. Doping a semiconductor, everybody knew about. But this doping of graphite, improving the conductivity by orders of magnitude, really intrigued her, and the physics of that had not been really looked at at all.

People looked at that and reported that phenomenon from the chemistry point of view, but this electron transfer, how the conductivity matters, the energy-band structure, all the physics of that had not been addressed. Millie decided to get into that field. It was new for her, that field of graphite intercalation compounds. And I was her very first graduate student in that field. I remember when she first told me to go into that subject, she just simply cut out pieces of chemical abstracts. She would Xerox and cut out pieces of abstracts of review papers mainly and paste the pieces of chemical abstracts on a piece of paper, and she handed me that piece of paper. That's how I started my research in that field. [Laugh]

ZIERLER: The same question I asked you at the beginning of our talk about applications versus fundamental research, what were Millie's motivations in that regard? Was she thinking about applications, or was this pure, basic science for you and her?

CHUNG: Millie's mind has always been basic science, and that's always been what captivates her. She used the applications as an excuse for doing basic science. [Laugh] That was what she said. Say, you write a research proposal to NSF, for instance. You want to do all that basic science, and then you describe all the applications to support that endeavor. She said, "That's just an excuse." [Laugh]

ZIERLER: Did Millie strike you as tough? Did she need to be tough as a woman operating at that level in science?

CHUNG: Yes, she was tough. And it was a new field for her. The only other group in the country that worked on this subject was in U Penn. They were our competitor. And I was her only student in this subject. She was invited to give a seminar at U Penn on this subject. Before she went, we met, and she told me, "I'm ready for anything." [Laugh] This implies that she really studied before the seminar and got ready, then convinced herself she was ready. It was a challenge for her. She didn't use the word challenge, but by saying, "I'm ready for anything," it implied that she felt that to be a challenge, and she was full-force in the confidence in facing that challenge.

ZIERLER: When did you know you had enough to defend? When did your thesis research feel like it had reached something approaching completion?

CHUNG: It was because my thesis had to do with several different aspects of graphite intercalation compounds, like the structural, electronic, and the optical aspects. I had these under control, and that's why it was natural that I felt I was pretty much ready for finishing up.

ZIERLER: What were your conclusions or contributions, looking back, with your thesis research?

CHUNG: The contributions had to do with the electronic and optical behavior, which were pretty new in this field dominated by chemists. And one of the biggest surprises we found was that the energy-band structure was not that greatly modified by the intercalation. Before we embarked on this research, Millie thought that the energy-band structure of graphite would be very much affected by the intercalation, but to our surprise, it was not. It was a negative observation. In fact, that was my very first paper, a negative observation. [Laugh]

ZIERLER: Who else was on your thesis committee besides Millie?

CHUNG: Probably Professor Kaplow and Professor Johnson. Millie was in the Electrical and Computer Engineering Department, but my home department was Materials Science and Engineering. Even though Millie was kind of the chair of the committee for my dissertation, there were a couple professors from the materials department on that committee.

ZIERLER: You saw Caltech through the eyes of an undergraduate and MIT through the eyes of a graduate student, so it would be very different to compare them. Still, I can't help but ask, how would you compare the Caltech experience and the MIT experience in science and engineering?

CHUNG: MIT has a much larger population than Caltech, and that larger population enables MIT to cover a larger number of fields in science and engineering. Especially in the engineering aspect. Caltech tends to excel more in basic science. But in terms of engineering, MIT has a lot of stuff, partly because of having a lot of people. But when you do a dissertation, you're bound to one field anyway. In a way, there's more to choose from before one decides. But to me, the biggest difference between Caltech and MIT was the atmosphere. Caltech is very personal. You feel like a big family. You feel like people know one another. But at MIT, it's quite impersonal in that regard. A lot of people walking around. You don't feel like a big family. I think that kind of atmosphere is particularly tough for undergraduates.

ZIERLER: I wonder what advice Millie might have given you if she saw that you would go on to accomplish important things in science. Did you have any of those kinds of discussions on a personal nature?

CHUNG: Millie and I both remained in the carbon field. I was her only student that remained, all these years, active in the carbon research field. Through carbon conferences, we met regularly, and when I received the Pettinos Award, a triennial international award, from the American Carbon Society, she told me that she and the others at MIT were very proud of me. She gave me an email on that. However, my and Millie's research interests deviated after I left MIT. I got into structural materials, and that's not her cup of tea at all. She was purely in electronic materials. We did not collaborate in research because we did different things. However, we both contributed to carbon science in different ways.

ZIERLER: When you graduated, when you defended your PhD, were you looking at both post-docs and faculty positions?

CHUNG: No, I was just looking at faculty positions. Perhaps in those days, post-doc experience was not as essential as today to land on a faculty position, so I didn't do a post-doc.

ZIERLER: What kinds of programs were you considering, given that the fields you could've gone into, materials science, metallurgy? What programs were most compelling to you?

CHUNG: Well, obviously, materials science. Because that really was the discipline of my PhD. But it's a discipline that is being challenged. Everybody pretty much realizes materials are important for all aspects of technology. It's the foundation of technology. A lot of researchers got into materials research without studying materials science. They might've studied chemistry, physics, mechanical engineering, civil engineering, but not materials science. Then, they just skewed their research to materials science. Then, as time went on, they'd get viewed as materials scientists, but their bag was not materials science. That's a challenge the materials science field has been facing for a couple of decades already.

ZIERLER: Tell me about joining the faculty at Carnegie Mellon. What was your focus? What was attractive about Carnegie Mellon?

CHUNG: Carnegie Mellon, at that time, was not a top university. Nowadays, it's very highly ranked. But in those days, it was not particularly highly ranked, but it was a very good school. Millie had some friends there, and she helped me get that position, actually. But Carnegie Mellon has always been very strong in materials, metallurgy in particular, traditional metallurgy. Iron and steel city. That strength in materials was one reason I chose Carnegie Mellon.

ZIERLER: Your interest in becoming more applied, going into materials science, did that happen right away, or was that a more gradual process?

CHUNG: Oh, it was gradual. It took maturation to really be able to appreciate the needs of technology in various industries. One needs to have a breadth of appreciation of the needs of various industries. And I gradually built up that breadth. It was gradual. In the beginning, I was just doing basic science, like what Millie has always been doing. But as I moved on, luckily, I was able to marry the basic science with the applied science.

ZIERLER: Were there any other women faculty members in the sciences or engineering at CMU when you joined?

CHUNG: Very, very few. I was the only one in the Materials Department. In electrical, there was one. Very few, and that was typical in those days. [Laugh]

ZIERLER: What was it like setting up your lab, and what were the most important funding agencies to gain support for the research you wanted to do?

CHUNG: Well, I was starting off, and for perhaps 10 years, I was very much concentrated in studying graphite intercalation compounds, extending my dissertation research. And I was successful in getting grants from the National Science Foundation, Department of Energy, Air Force Office of Scientific Research for studying graphite intercalation compounds. However, after about 10 years, this field gradually withered, declined.

ZIERLER: What accounts for that?

CHUNG: Because the applications did not quite work out. I told you before that the conductivity gets increased by orders of magnitude, but it was still a little bit lower than that of copper. [Laugh] It's lightweight and so on, but it's still below copper. Conductivity alone would not make it a viable application. The field declined, and the funding declined. I was faced with a real challenge at that time. I was still very young. I could still go on and remain a world authority of a withering field. [Laugh] I could have chosen that route. But I decided to leave that field. Very difficult decision.

ZIERLER: I wonder if that experience informed how you look about revolutionary advances in science.

CHUNG: Exactly. It was leaving that only field of expertise of mine that forced me to jump out of my comfort zone. It was at that point that I started the cement research, and then I got into microelectronic cooling, vibration damping, and all that. But that was a critical moment that forced me to jump out.

ZIERLER: What was the game plan at that point? How would you break into this new field? What would you need to learn on your own, and where could you rely on collaborators to help you get going?

CHUNG: I got interested in cement, but I was interested in not the usual structural and durability aspect that everybody in the cement field had been looking at. I was interested in the functional property, particularly the sensing behavior. Nobody had even dreamed of that. Getting into a new field, such as concrete, and embarking on a new aspect of research in that new field was not easy. This field has always been very traditional, the concrete field. In the beginning, it was not easy. I'd write papers, trying to get published, and the reviewers would complain about various things because they seemed to think that this was just not according to what they would conventionally do. They're very strict about the conventions in the field of concrete, how you mix, the details of the mixing, all that. I had some difficulty in the beginning, and as years went by, I got past that.

ZIERLER: Was the decision to go into a new field related to your decision to transfer over to Buffalo?

CHUNG: Not really. The reason I wanted to go to Buffalo is because of my parents, who lived in Toronto. Buffalo was the closest point in the US to Toronto. That was the main reason I moved. At that time, Carnegie Mellon was not that highly ranked. That move also allowed me to start in a new field, namely the concrete. The concrete research I did started in Buffalo.

ZIERLER: Tell me about creating the Composite Materials Research Laboratory at Buffalo. What were the motivations there?

CHUNG: I wanted to have an entity that is close to my research. And composite materials is kind of an umbrella because I deal with cement-based composites, polymer-based composites, and later on, metal-based composites. It's kind of an umbrella that covers my breadth of research. Another reason I wanted to have an entity is that my department is called Department of Mechanical and Aerospace Engineering. The word materials is not in it. I wanted something with the word materials in it. [Laugh]

ZIERLER: As you got your research up and running at Buffalo, what were some of your funding sources?

CHUNG: The major grant I obtained was from DARPA, the Defense Advanced Research Projects Agency, and that was on microelectronic cooling, what I talked about in terms of thermal interface materials and so forth. It was very interesting or unusual that I was able to get that big grant because I was the only investigator in that grant, the only PI. There was another university with 24 professors competing with me for that DARPA funding, and I got it. [Laugh] It felt miraculous. That grant helped me a lot in establishing my research and broadening it further.

ZIERLER: When did you start to think about sustainability, energy, or even climate-change issues?

CHUNG: Climate change is in the minds of everybody nowadays, and the funding agencies really emphasize that. And much of the emphasis is on renewables in the forms of wind and solar. But there are inherent problems in these because both wind and solar only give you energy intermittently. No wind, no energy, and similarly for sunlight. You have to store the energy when it's there, so you need energy storage to go along with that. Energy storage involves batteries, so you need big banks of batteries, which are not only expensive but take up a lot of room. And the durability of the wind turbines and solar panels is another issue. Wind turbines tend to fail within five years of installation. And it takes a huge amount of money, tens of thousands of dollars, to replace one blade. I'm now embarking on research to do defect sensing, damage sensing, for those blades, which are made of glass fiber composites, with the hope of early detection of damage so that the repair can be timely. I'm also looking into alternatives to traditional energy sources.

ZIERLER: Tell me about building your research group, the kinds of graduate students who would be attracted to work with you.

CHUNG: Well, students tend to be attracted to applications. The fact that my research has clear linkage with applications helps a lot in attracting students. I think the success of any graduate student depends a lot on the research topic. If the research topic is a good one, that is, impactful as well as doable, it's great for the student. But if the research topic is kind of mundane or even not very doable within a few years, the student can have a terrible time. They might even get disillusioned. The choice of topic is crucial for the success of a graduate student, and that choice should be largely made by the professors. Because the students are just not experienced enough to realize what topic is both worthwhile and doable, and how to narrow that topic so it becomes one doable piece. The students alone cannot make that decision. They just don't have the experience to do that. The professors need to do that. Because I have all these ideas having application related to the basic science, my students tend to be kind of lucky in that they can complete their dissertation without a whole lot of headache. [Laugh]

ZIERLER: I'm curious, did Millie provide a model to you on the kind of graduate advisor you wanted to be?

CHUNG: She did not advise me specifically on that when I was a graduate student, but as I observed her work through the decades, it was very clear that she was very much on top of the latest development and would be one of the first to get into whatever was the latest. I remember she told me that she was in her 70s when she first got into research on graphene. Not because she was late, just because graphene was not popular in research until the last 20 years. And once it became known that graphene was really worth studying, especially in the electronic behavior, she moved into it right away, even though she was in her 70s.

ZIERLER: And that's a model. It's always interesting, it's always an opportunity to break into new fields.

CHUNG: That's right, irrespective of your age. [Laugh]

ZIERLER: After you joined Carnegie Mellon and the first 10 years, from when you decided to switch fields, and then in light of looking back on all the things you've accomplished, when do you feel like you really started to make an impact in this new field, either by publication, or citation, or even awards? When did you feel like you were really starting to make a difference, even though you were a newcomer?

CHUNG: In terms of my overall career accomplishments, I have to say that the smart cement is what I'm known for. It's pretty clear that researchers all over the world recognize me as the inventor of smart cement or smart concrete. There's no question that they all attribute that to me, at least in the papers they write. [Laugh] I invented that in 1993, and a lot of papers have come out since then by researchers all over the world. In that sense, it's gratifying.

ZIERLER: As the founder of a field, what has surprised you about how it's matured? What directions has it gone into that you might not have seen in 1993?

CHUNG: There are many issues that need to be dealt with before applications can be realized. For instance, I study the thing in the material level, small specimens in the lab. However, concrete structures are big. The move from studying it on the material level to the structural level is a necessary and big step that needs to be done. Also, studying the effects of various environmental factors, like humidity and so on. A lot of work has come out since my 1993 paper because there's a lot of stuff that needs to be covered.

ZIERLER: Do you see the applications yet? When we go out into the real world, do we see any of these applications? Or things are still in development?

CHUNG: Actually, I have recently reported a new development. The old development of mine requires the addition of short carbon fiber, a small amount of that, into the concrete in order to render that self-sensing ability. And because of the addition of the carbon fiber, it limits it to new structures, not existing structures, which would not have the carbon fiber. However, in recent years, I have gone into not electrical-resistance-based sensing but capacitance-based sensing. And for the capacitance-based sensing, that is, measuring the capacitance to get information on the strain, deformation, or damage, the concrete does not need to be conductive. One does not need to add any carbon fiber or whatever conductive additive to it. One can do the sensing without any additive and obviously without device incorporation, involving capacitance measurement rather than resistance measurement. In the recent few years, I've been exploring that.

ZIERLER: What are you most excited about? Where can the field go from here?

CHUNG: With the capacitance measurement, and the absence of need for any additive, the application can involve existing structures. However, one catch is that moisture or water affects the capacitance a lot. But for indoor applications or deep underground applications, as in oil wells, which also need cement, the water content doesn't change. Under that situation, there's no problem with the sensing technology based on capacitance measurement and involving no additive. I envision that the application in buildings and deep underground wells to be viable using this approach.

ZIERLER: And this is your current research focus?

CHUNG: Yes, that's right.

ZIERLER: What are the prospects? Where are you optimistic? What are the challenges?

CHUNG: For any of these big structural applications, one needs to move from the material level to the structural level. I'm still doing it on the material level. One needs to, say, go to a real building and demonstrate the ability to sense there. There are steps involved. [Laugh]

ZIERLER: Now that we've worked right up to the present, for the last part of this wonderful conversation, I'd like to ask a few retrospective questions, then we'll end looking to the future. First, to go back to Caltech, have you been an engaged alumnus? Have you stayed in contact with your friends and colleagues over the years?

CHUNG: I've been in contact with Caltech as an alumnus all these years. And I have a couple of friends who also graduated from Caltech that I also keep in touch with. Sharon Long, one of the first four women graduates, I keep in touch with her. I cherish all these relationships.

ZIERLER: You alluded to it before, but it bears a bit of a longer answer, what you learned at Caltech that's stayed with you, either in collaborations, the approach to science and engineering. What has been so important for you, being an undergraduate at Caltech?

CHUNG: I really think that the breadth of basic scientific education and the early experience in research. Those are two very valuable things that Caltech provided me and that have been very important for my career.

ZIERLER: Unfortunately, we recently lost Millie Dresselhaus. Have you had opportunity to reflect on her career and impact?

CHUNG: Oh, yes. I think her biggest impact has to do with her theoretical analysis of carbon nanotube and predicting the electronic properties of the carbon nanotube before people experimentally observed what she predicted. And a certain structure of the nanotube is a metal. Another style of a nanotube as a semiconductor, for instance. She's done such theoretical work on graphite, so it was easy for her to kind of jump from graphite to carbon nanotube, and then later jump to graphene. Especially for the nanotube, I think this is her biggest impact.

ZIERLER: In all the ways that you have been recognized, with awards, lectures, visiting professorships, what's been most important to you in the way that it's allowed you to do new research or just in the satisfaction of being recognized for the kind of research that you've done?

CHUNG: Obviously, being recognized is important. And collaboration is important. And because of people recognizing me for what I have done, visiting scholars come to my lab from all over the world. [Laugh] They just knock on my door, wanting to come to my lab to do research. I think that's wonderful. To be able to work with not just graduate students and post-docs, but work with these somewhat matured researchers and professors. That is possible because they know me.

ZIERLER: What have been the most important academic societies or editorial positions in journals for you over the course of your career?

CHUNG: Well, the journal Carbon is the premier journal in carbon, and I've been involved with that, on the advisory board for some decades. I do reviews of manuscripts a lot for many, many journals. And it takes me a lot of time to review so many manuscripts that have been submitted to journals and are directed to me for review, but I feel it's very important to make sure that flawed papers don't get published. And there are so many possible flaws, some of which I alluded to. That's a substantial part. I almost review a paper a day. [Laugh]

ZIERLER: In reflecting on your contributions, both in basic research and in applied science, how do you compare the satisfactions between discovering something in nature versus creating something for societal benefit?

CHUNG: I don't really study natural materials that much, like plants and proteins. I don't really do that. All the materials that I study are not natural materials but manmade materials.

ZIERLER: But the way that you study them does yield insight into natural processes, how things behave.

CHUNG: Well, the properties of the synthetic materials can shed some light on the properties of natural materials. But that's not something that I specifically study.

ZIERLER: One last question. What haven't you yet accomplished? Thinking about Millie in her 70s, taking on a new field, is there anything new that you want to accomplish that you haven't accomplished yet?

CHUNG: I am currently working on two areas. One is the capacitance-based sensing as applied broadly to many, many materials applications. Not just concrete, but wind turbines, steel structures, automobile structures, and so on. Another area I'm currently working on is a new type of energy source, an untapped form of energy that I have discovered in the last few years. It's a low-power energy source, but it's new, untapped, and it's all over the place. And that's something very revolutionary, and I'm working on that.

ZIERLER: That's exciting, indeed. On that note, it's been a great pleasure to spend this time with you. I'd like to thank you so much for doing this.