Mahendra Kumar Sunkara
Director, Conn Center for Renewable Energy Research
Professor of Chemical Engineering
University of Louisville
Louisville, Kentucky, USA
- Ph.D., Case Western Reserve University, Cleveland, OH, USA
- M.S., Clarkson University, Potsdam, NY, USA
- B.Tech., Andhra University, Waltair, A.P., India
Advice to Students:
“Explore training with scanning electron microscopy and start making observations.”
Conn Center for Renewable Energy Research
Mahendra Kumar Sunkara directs a R&D center to address grand challenges in solar photovoltaics, solar fuels, biofuels and energy storage and advanced energy materials. Conn Center has core staff of 12, of which eight are eminent researchers, leading various themes and four administrative/technical staff to support various center’s activities. Conn Center also maintains unique R&D facilities spanning over 20,000 sq.ft lab space which include advanced materials characterization, materials manufacturing, energy device prototyping and testing and scalable manufacturing facilities for solar, energy storage and biomass and biofuels. The center also plays a vital role in defining innovation in the upcoming research park and the institute for product realization.
Q: When did you first find that your career path focused on nanotechnology?
Sunkara: In my graduate studies, I became fascinated with the nucleation and growth mechanisms for crystals in electroplating and chemical vapor deposition. During my PhD, I looked at nucleation of diamond crystals from the vapor phase and started looking at small crystals and the role of defects and growth mechanisms on the final morphology, growth kinetics and ability to grow large single crystals. This led to a significant interest in investigating the structure and morphology of nanoscale diamond crystals. When I started out my academic career in 1996, I initiated a research program on nanowires and nanoparticles using plasma assisted chemical vapor deposition processes and started investigating scalable manufacturing processes for one-dimensional materials and their performance with various energy conversion and storage applications.
Q: What current nanotechnology applications are you working on?
Sunkara: We are probably one of the very few research groups around the world that is focused on scaling up nanowire production – powders at a scale of several Kgs per day and vertical arrays over large areas. Because of these unique capabilities, we are currently focused on using them for solar fuels, electrocatalysts, and heterogeneous catalyst and carbon dioxide adsorbent applications. Our group has done some unique work on kinetic monte-carlo simulation of one-dimensional growth, new 2-D materials, proposed and rationalized growth of one-dimensional crystals using non-conventional processes such as self-catalysis, growth using non-catalytic metals and vapor-solid mechanisms and also developed unique processes that are highly scalable with reaction time scales on the order of few seconds.
Q: What’s the most rewarding thing about working with nanotechnology?
Sunkara: There is never a dull day in lab when working with nanomaterials and their integration into various applications. The use of engineered one-dimensional materials allowed us to improve the performance of several energy conversion and storage applications by an order of magnitude compared to the state of art. In addition, the synthesis of nanoscale materials also allowed us to synthesize some unique materials which otherwise are considered as metastable and can not be made using traditional techniques. For example, the investigation of small carbon structures led us to provide insight into the structure of n-diamond phase. Similarly, there are many more examples with new materials formed during transforming one-dimensional materials from one composition to another. So, the opportunities seem endless and it is possible to think of a number of applications using nanoscale materials and processes.
Q: Is there an example you can provide that shows how something you’ve worked on has positively impacted the world?
Sunkara: There are many examples. One primary example that I will provide is our invention of the concept of using non-catalytic metals (for example, gallium) for growing one-dimensional materials such as silicon nanowires led to a number of scalable processes for growing nanowires. Until this time, researchers believed that it is essential to have catalytic metals such as gold and iron to grow 1-D materials. Our inventions and process concepts led to scalable manufacturing processes for making nanowire powders in large quantities and arrays over large areas. One of the catalyst products based on ZnO nanowires is being commercially made available through the startup (Advanced Energy Materials, LLC) for removing sulfur in diesel and other fuels from several hundred ppm to 1 ppm. This product will be implemented world-wide in the next one to two years time frame.
Q: What do you think is the single greatest impact nanotechnology has had on the world thus far?
Sunkara: It is difficult to pinpoint to one application or area in which nanotechnology made an impact. Rather, nanotechnology had ubiquitous impact in many applications ranging from thin films for displays, composites, energy conversion and storage, chemical and biomedical sensors and medical therapies.
Q: Please give an example of what you envision nanotechnology applications leading to in the future.
Sunkara: Future applications will involve engineered devices and sensors involving nanoscale materials and processes on flexible platforms and device fabrication on-demand and as-needed basis on a global scale.
Q: Do you find yourself working more in a team situation, or more alone?
Sunkara: I led a team at University of Louisville. In some cases, I collaborated with several scientists from other institutions such as Dr. Meyya Meyyappan at NASA Ames, Dr. Madhu Menon at University of Kentucky, Dr. Miran Mozetic/Dr. Uros Cvelbar from Institute Jozef Stefan, etc.
Q: If you work more as a team, what are some of the other areas of expertise of your team members?
Sunkara: My collaborators from Institute Jozef Stefan had great expertise with plasmas and plasma processes; colleague from NASA Ames had great knowledge on nanowires for sensors and devices; and colleague from University of Kentucky had great expertise in the use of computational techniques for prediction of new materials such as new 2-D materials.
Q: Were you interested in science or engineering as a child? What was your experience then?
Sunkara: I was always stood first in my class since childhood and was always interested in science and engineering career. Of course, i did not have much exposure to research during my school days. I have always been fascinated with research and making technical discoveries.
Q: Did your university training help you in your nanotechnology work?
Sunkara: During my PhD at Case Western Reserve University, I had great mentorship and training under the supervision of Professor John Angus. He taught me on how to think in terms of atomistic mechanisms for crystal growth and grew my interest in exploring nucleation and growth of solids. He inspired me to question the obvious and encouraged me to think different.
Q: If you had to do it all over again, would you still focus on nanotechnology applications?
Sunkara: Yes. I would still focus on nanotechnology applications. This length scale is interesting for both materials and processes. It connects the molecular world to macro-scopic world while influencing the behavior of materials and devices greatly.
Q: If a high school or college student was interested in nanotechnology, what advice would you give them to help prepare take on those roles?
Sunkara: In my role as University Professor, many high school and undergraduate students approach me with interest in nanotechnology. I recommend them to first train with scanning electron microscopy and start making observations. If they are pursuing a degree then I would strongly recommend them to take a variety of courses including materials characterization, solid state physics, optical and electrical properties and computational materials science if possible.