FOCUS ON NEW FACULTY:
Assistant Professor David Rothamer
 or new Assistant Professor David Rothamer, working at the College of Engineering is like coming home.
The Spencer, Wisconsin, native received his BS (’00) and MS (’02) from UW-Madison, working within the Engine Research Center (ERC) as a graduate student. His then-advisor, Professor Jaal Ghandhi, now occupies the office next door to Rothamer’s own. Across the hall is the office of Assistant Professor Scott Sanders, who came from the same research group that Rothamer spent six years in while earning his PhD at Stanford University.
“I had a really good experience here as an undergrad and in grad school,” says Rothamer. “I knew I’d like the environment. Plus, in terms of doing research on engines, the ERC is the foremost place to do that in the United States.”
Rothamer’s research focuses on optimal fuels to use in combustion engines, specifically in two directions: chemistry and thermodynamics. Chemically, he is interested in how the structure of the fuel relates to emissions formations, especially soot. “It’s pretty amazing that in the engine you can go from having fuel to, in a matter of milliseconds, having soot, even though it’s an extremely complex process to go from one point to the other,” he says. “We don’t really understand a lot of the points that happen in between.”
To understand the fundamental chemical process, Rothamer applies laser diagnostics to take measurements of fuels in a basic burner, looking at different intermediate compounds, how they form and how they contribute to soot formation.
In addition to chemical structure, Rothamer studies how thermodynamic properties of fuels affect engine operation. The amount of energy needed to vaporize a fuel, called heat of vaporization, influences the temperature of the fuel-air mixture in-cylinder. An engine running on a fuel with a higher heat of vaporization can have higher thermodynamic efficiency.
Such considerations are very important for biofuels such as ethanol. Most of the energy required for ethanol production, whether from corn or other sources, goes into separating ethanol from the water. This energy-intensive process is a major obstacle in making ethanol a cost-effective gasoline alternative. However, having some water in the fuel actually may be beneficial for the engine due to water’s high heat of vaporization. Increases in thermo-dynamic efficiency can help offset the energy potential displaced by having water in the mix. Therefore, not removing all the water could create a fuel that performs as well as pure ethanol but is much easier to produce. “The question becomes, how much water can we have in the ethanol?” asks Rothamer.
As technology advances, Rothamer hopes to continue to explore the fundamental properties of fuel and develop tools for diagnostics. “It’s a really exciting time because there are a lot of opportunities and a lot of challenges in the engine community,” he says.
FOCUS ON NEW FACULTY:
Assistant Professor Ryan Kershner
 ssistant Professor Ryan Kershner is ready to dive into collaborative research. “One of the fastest ways to get started is to jump in and collaborate with people,” he says. “Just the idea of having the ability to work with people from all over campus is really exciting to me.”
Kershner, who joined the department in January, received his PhD from MIT in 2004. Prior to coming to UW-Madison, he did research at the University of Illinois and worked at IBM. The interdisciplinary nature of the College of Engineering and the opportunity for applied research drew him to UW-Madison. “People being willing to share their ideas and talk in interdisciplinary terms is really great. It’s just exciting to be able to brainstorm,” he says. “That’s the kind of campus this is.”
While Kershner’s enthusiasm is for broad, cross-disciplinary science, his research focuses on the very tiny—assembling and manipulating nanoscale structures.
Researchers use a variety of techniques to build structures on the molecular level in ways that don’t occur spontaneously, called directed assembly. Kershner takes a slightly different approach than most, choosing to use external fields to control structures sized between 100 nanometers and one micron—
a millionth of a meter. One such area is developing and using laser tweezers, devices that manipulate matter with light. A different technique uses electric fields.
Another method, used often for biological nanostructures, is directed self-assembly, or using known properties and reactions to achieve a desired result. One example is “DNA origami,” a technique Kershner explored while at IBM and plans to continue researching at UW-Madison. The process folds a long strand of DNA into a specific shape or surface, then bonds it in place with smaller pieces of DNA. This technique could be valuable for building tiny, fast computer chips or other surfaces for sensors or medical diagnostics.
In addition to his appointment in mechanical engineering, a department he was attracted to for its reputation for applied research, Kershner also participates in the interdisciplinary Materials Science Program. This affords him opportunities to pursue collaborations and share resources with faculty and students from other departments, enabling him to more aggressively pursue his research.
“I’ve always been kind of a jack-of-all-trades, but very tied into the science,” he explains. “The science is very interesting to me because it allows you to explore new problems. The applications come down the road, but you have to get the basic science down before you can apply it.”
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