What sparked your initial interest in engineering?

Throughout my youth, I was interested in designing cars and planes. While I was at Seoul National University, there was a popular television programme about an Air Force pilot. It inspired me to focus my interests on planes and gain acceptance into the aerospace engineering department at my university.

Did you explore opportunities in foreign countries?

Yes. To satisfy my military service requirement, I earned my masters at Seoul University while working for the Korea Aerospace Research Institute. To gain the international experience I thought I needed to pursue aerospace-training opportunities abroad, I became a lecturer in a Korean-government overseas volunteer programme. I lectured on Korean languages and computer science in Thailand, which gave me confidence that I would do well in other countries.

How did you move into nanoscience?

After my lecturing service, I discovered that aerospace-engineering schools in the United States were shrinking their programmes. So, I decided to switch gears and apply to schools with PhDs in micro- and nanoscale systems, because interest in these areas was booming. I gained admission to four US schools, but I wanted to work with Kenneth Breuer, a fluid-mechanics researcher who had been developing microscale engines for satellites. I contacted him to express my interest. He liked my work, and said he had moved to Brown University in Providence, Rhode Island, and was looking for a new student. He helped me secure admission and full support within a month.

What was your most pivotal career decision?

I chose to switch schools halfway through my PhD. At Brown, I was measuring flow phenomena in microfluidic devices I designed — an interesting project, but predominantly experimental. I preferred designing and making devices. I started studying the work of Chang-Jin Kim at the University of California, Los Angeles (UCLA), who was famous for the design and fabrication of micro-electromechanical systems. When I contacted him to ask about research openings, he invited me to join his lab. It was a very hard decision. Ultimately, Breuer said he wouldn't prevent me from exploring what I really wanted to do. He asked only that I finish my current project and publish the results. That paper is highly cited and considered a classic reference paper in microscale fluid dynamics (C. Choi et al. Phys. Fluids 15, 2897; 2003).

Why didn't you do a postdoctoral fellowship?

When I was about to finish my PhD, I still hadn't published all of my major results. But because I had already spent two years at Brown and almost five years at UCLA, I worried that one or two more years for a postdoc was too long. I applied for faculty jobs even though I didn't expect much without postdoc experience. Fortunately, the Stevens Institute of Technology was eager to hire faculty members in nanoscale engineering and saw the potential of my work on superhydrophobic surfaces.

How did you differentiate your work from that of your mentors?

When I came to Stevens in 2007, I didn't want to compete with either of my previous advisers, so I decided to look for different applications for these superhydrophobic structures. I discovered that there was a need for anti-corrosive materials in ships and planes. I wanted to use our materials to reduce metal corrosion by minimizing liquids' contact with metal surfaces.

How did you secure funding from the US Navy?

Initially, US funding agencies thought my ideas were interesting but not practical enough to fund because I couldn't make nanostructures on a large scale. This challenge prompted me to develop ideas for creating nanostructures on the much larger metre scale. The engineering dean at Stevens connected me with a Navy programme manager who helped me to secure a year's funding for exploratory work. If I could prove myself, she thought I had a strong chance of securing more funding through the US Navy Young Investigator Program.

How do you think this award will affect your career?

I think it helps position me for tenure because my school holds the award in high esteem. The ONR selects only 10–20 people from more than 10,000 applicants. It is a great honour, especially because I am a foreigner.