On the second floor of Case Western Reserve's A.W. Smith Building, a name resonates through fluorescentlit laboratories crammed with jury-rigged assemblages of tubing, dry ice and laptops. To be sure, the names of pioneering scientists such as Curie and Faraday also are invoked here. But this name applies to a presentday chemical engineering professor whose work with students has earned the university's highest honors for mentoring: It's Mohan.
The slender and soft-spoken 39-year-old scholar inspires an energetic team. Mohan Sankaran, PhD, professor of chemical and biomolecular engineering and associate director of the university's Swagelok Center for Surface Analysis of Materials (SCSAM), holds a secondary appointment in the Department of Materials Science and Engineering. To his colleagues, he is an innovator advancing understanding of a revolutionary method of forming microscopic diamonds. To his students, he is a sounding board, advocate and guide who turns plasma science into a fascinating quest.
Making nanodiamonds requires a particular kind of faith. That's partly because the size of each particle is infinitesimal: measured in nanometers, rather than carats. You'd need 50,000 of them to equal the width of a human hair. To the naked eye, a few micrograms caught on a filter look like the stubbed ash of a cigarette. Even magnified 800,000 times through an electron microscope, the crystals are mere shadows. Yet they have the exceptional properties that have drawn people to the traditional stone for centuries. Nanodiamonds are incredibly strong, transparent and unparalleled at conducting heat and sound. Sankaran's bet is that his lab-manufactured diamonds could spawn a wide range of low-cost applications, from delivering drug therapies at the cellular level to making coatings for plastics and electronics.
Chemical engineering students—both undergraduate and graduate—are an essential part of the quest. But working with such minute particles can be daunting. "It takes patience," said Joseph Palmeri, a junior and student on scholarship from Williamsville, N.Y. An active researcher in Sankaran's lab since his first semester on campus, Palmeri uses a plasma reactor that he built to boost the nanodiamond production. "We've been working on this project for a year, and we're just starting to see results." The lab recipe for nanodiamonds upends the way nature creates them underground.
Instead of cooking carbon at 2,200 degrees Fahrenheit and applying 750,000 pounds of pressure, Sankaran's team uses low (atmospheric) pressure and temperatures to fuse the carbon molecules. Introducing a thin stream of super-cooled methanol or ethanol into a flow of charged argon gas triggers a reaction that severs the carbon molecule from the alcohol. The carbon atoms form strong three-dimensional bonds. Voila: nanodiamonds.
This revolutionary approach continues a tradition of diamond synthesis at the university started 50 years ago by Case Western Reserve's John C. Angus, PhD, now Kent Hale Smith Professor Emeritus of Engineering.
"He started talking about nanodiamonds with me when I first started," said Sankaran, who noted that Angus still mentors him. Like many others, Sankaran felt an irresistible draw to the fascinating material but knew how difficult it was to create. "The challenge of making it and the possibility of developing a new technique for it were a scientific itch that I had to scratch," he said.
Now, Sankaran's team is digging into the variables of the optimum chemical reaction: How much methanol? What gas flow rate? How much pressure?
"The first step was making sure we could make [nanodiamonds]. Now, the goals are to reach an optimum level of size and purity and increase the production amount," Sankaran explained. "We can make the material on the order of micrograms. But to supply them to other groups, we need to get to gram quantities."
The goal is straightforward, but the process of reaching it is not always so clear. Sankaran's role as a mentor requires that he balance providing answers with encouraging student exploration.
"I've sometimes left here at 10 p.m., frustrated," Palmeri admitted. But Sankaran's quiet persistence is a motivator. "He encourages us to think and come up with new solutions, but he wants us to take our time and do things thoroughly," Palmeri said. "That's an important skill I've learned."
Sankaran describes his mentoring style as "tough love."
"But I want to do it in positive way," he added. "The reason I'm tough is I want them to aspire to be better than me. The process of trying to do that is a good thing. What it means to me in research is I don't put any limit on what they can do. I try to overcome their concerns about their own performance. That's sometimes the difficult part. I try to give them steps. They're not limited to do just what someone else tells them."
A California native, Sankaran was raised in Cupertino. Though his father was a materials scientist, the son spent his high school years honing his skills in debating; it wasn't until he enrolled at University of California, Los Angeles, that he was drawn to chemical engineering.
"I guess it was in the genes," he laughed. By sophomore year, he was working with Professor Harold Monbouquette, whose encouragement and groundbreaking research in molecular engineering sparked Sankaran's desire for an academic career of his own. After graduating in 1998, he attended California Institute of Technology, earning his doctorate in 2004, and joined the Case Western Reserve faculty the following year. Among the early campus mentors he now counts as friends is Daniel Lacks, PhD, C. Benson Branch Professor of Chemical Engineering.
"The first thing he did that was just great—he invited me to work on a project on understanding electrostatics at the physical and chemical level," Sankaran recalled. "It was not related to my prior work, but it led to work in a new area that I continue to work in."
Lacks agreed. "My expertise is with theoretical techniques, while Mohan's is with experiments," he said. "We've since had many other projects based on this combined theoretical-experimental approach, as well as unrelated academic projects. We really work well together."
The collaboration also led to a new international effort. Student engineers now travel annually to work on projects with faculty at the University of Botswana in Gaborone and build solar arrays to generate power in rural villages. Sankaran advises students in the chemical engineering department who are interested in study abroad programs, which can help develop undergraduates into seasoned researchers.
Sankaran has learned that good undergraduate researchers bring unique insights and talents that move the work forward. "Research can be pretty hard. You're on your own a lot. The mental approach is more important than the skills," he said.
When Joe Toth (CWR '15) first approached Sankaran about joining the research team, Sankaran was intrigued to learn that his upbringing on a family farm had taught Toth machining skills. Those had immediate applications in the lab, as well as in field experiences in Botswana. Senior Amy Aube had a talent for building digital electronics, which proved essential in controlling and making measurements on her experiments. Matt Cochey (CWR '08) wrote a computer program that the lab still uses 10 years later.
Sankaran has inspired undergraduates to continue research careers. "I began working with Mohan the summer before I started my freshman year, and during the first meeting, I was sold on his mentoring style," recalled Megan Witzke (CWR '13), now a doctoral student at the University of Illinois Urbana-Champaign. "He created an environment for us to grow and flourish as researchers. By advising me to participate in the program for sustainable energy in Botswana, he [encouraged] my future research career in alternative and renewable fuels."
Witzke is one of three Sankaran students who have won prestigious National Science Foundation fellowships in the past five years. "Undergraduates in Mohan's lab win that highly competitive fellowship in numbers higher than entire departments at other universities," Lacks said. "This success is due to the world-class quality of his research, as well as his dedication to seeing undergraduate students develop as scientists rather than lab assistants."
Palmeri and graduate student Jon Cole work side by side in the Sankaran lab but address different aspects of the nanodiamond processing puzzle. Cole concentrates on creating a formula to optimize the purity of nanodiamonds because he must complete a specific project to prove a hypothesis for his doctoral thesis; freed of that requirement, Palmeri can tackle more open-ended tasks. He's testing ways to increase the production rate of the particles. By adjusting the power supply, as well as the flow rates, pressure and composition of the gas, he has succeeded in generating about 1.5 milligrams of material—some diamond, some in other forms of carbon, such as graphite—in about two hours.
As the lab's work gains momentum, Sankaran has begun to envision how nanodiamonds will be put to work. The final size of the particle suggests how it might be deployed, though he cautions that potential users have not yet defined their needs.
"In medicine, micron-sized particles can be absorbed into the body by breathing or the bloodstream," he explained. The 2-nanometer particles his lab is producing are exponentially smaller—different by a factor of 1,000. "So a nanodiamond could get through the pores of a cell to interact with proteins."
Commercial companies already have shown interest in using larger, micron-sized nanodiamonds for coatings, particularly for plastic and electronic components. The material's thermal conductivity could quickly cool delicate equipment.
As a true mentor, Sankaran is genuinely grateful for the opportunity to learn from his students. "They teach me a lot," he said with a smile. "I get as much out of the experience as they do."
The Mohan Sankaran Lab
Nanodiamonds are one of several applications the Sankaran Lab is investigating for microplasmas. These charged gases also enable television displays, lighting systems and pollution-control systems. On campus, graduate and undergraduate students are working on other projects using plasma at atmospheric pressure and low heat. They are:
Mohan Sankaran's version of Etch A Sketch: His team uses microplasmas to "write" patterns on flexible surfaces such as an electrical circuit. This collaboration with colleagues Christian Zorman, PhD (GRS '91, '94 physics), a professor of electrical engineering, and Philip Feng, PhD, an assistant professor of electrical engineering, is supported by a $1.2 million grant from the National Science Foundation and could speed the development of materials for flexible cellphones or implantable devices.
Scrubbing Up with Plasmas: Many large cities already use plasmas produced at high energy to purify their water supplies. However, the electrochemical interaction between plasmas and water is not yet fully understood. Sankaran collaborated with researchers at the University of Notre Dame on a recent paper in Nature Communications. The group reported observing electrons from a plasma made at atmospheric pressure as they dissolved into water. These powerful particles use far less energy and could inexpensively decontaminate polluted sites or purify water.
Awards and Honors
Mohan Sankaran's awards for teaching, mentoring and researching include:
- Case School of Engineering Tau Beta Pi Srinivasa P. Gutti Memorial Teaching Award, 2015
- Case Western Reserve University J. Bruce Jackson Award for Excellence in Undergraduate Mentoring, 2013
- CWRU AVS Peter Mark Memorial Award, 2011
- CWRU Camille Dreyfus Teacher-Scholar Award, 2010
- Young Investigator Program award from the Air Force Office of Scientific Research, 2009
- National Science Foundation Career Award, 2008