Everyone knows what happens when you put water in the freezer, but when it comes to understanding how the molecules behave as the liquid becomes solid, many of the cold facts remain undiscovered. Researchers at Clemson University are hoping to learn more by using state-of-the-art molecular modeling and computer science techniques. Their efforts could help develop new ways of preserving food, studying climate, cryopreserving organs and protecting crops.
Sapna Sarupria, an assistant professor of chemical and biomolecular engineering, is leading the five-year project with a $503,773 CAREER award from the National Science Foundation.
She and her team want to know more about how freezing occurs, so they are using advanced computational methods to zoom in and observe individual molecules as they transition from a liquid to solid form. The focus will be on the “birth” of the solid phase, known as nucleation, Sarupria said.
“If you really cool liquid down, it doesn’t instantly turn into a solid,” she said. “It takes a while. A nucleus has to form, just the right amount of that little bit of solid that will make the whole thing turn solid. That process is what we’re interested in.”
Everyone has been taught that water freezes at 32 degrees Fahrenheit, but that’s not always the case.
Some materials and conditions can cause water to freeze at higher or lower temperatures because of a molecular process called heterogeneous nucleation. In fact, pure water can be cooled down to minus 36.4 degrees Fahrenheit if done carefully.
Sarupria expects her research will begin laying the groundwork for new materials that could be added to water so that ice will grow at a specified rate and temperature. What makes her approach unique is that she will be using specialized software her team developed and Clemson’s world-class supercomputer (8th fastest academic supercomputer in the U.S.) to speed up sampling by more than a factor of 20. Her approach narrows down the options to the most promising materials, which can then be tested in a lab. Physically testing each possible material would take much longer and cost more.
“This research is transformative because it provides a computationally inexpensive pathway to screen materials for ice nucleation propensity,” Sarupria said.
The research shows high promise for improving food preservation. As much as one-third of the food produced in the world is lost to spoilage due to improper transportation and storage, while 842 million people remain chronically undernourished, according to the United Nations.
Food loss could be reduced with improved freezing technologies, Sarupria said.
“One approach includes using ice nucleating proteins to induce ice formation at higher temperatures, thereby reducing operating costs,” she said. Sarupria’s research involves collaboration with Clemson’s computer science experts, allowing her team to work more efficiently. “That allows us to do more with less manpower and computer time,” she said.
David Bruce, Chair of Chemical and Biomolecular Engineering, said the CAREER award is one of the nation’s top honors for junior faculty members.
“This is well-deserved,” he said. “The award is a testament to Dr. Sarupria’s hard work, creativity and cutting-edge approach to a field of study that could have tremendous effects on the global economy.”
Sarupria said she got the idea for the research after talking with some atmospheric chemistry experts from Princeton University.
When she asked what kind of questions they were interested in, their answer was heterogeneous nucleation. The process occurs in the atmosphere when dust and other particles combine with water vapor to form clouds, but many questions remain about its effects on climate and weather.
Sarupria said she was fascinated at how little was known about an occurrence as common and basic as freezing.
“You would think that we know water, but we really, really don’t,” she said. “Water does whatever it wants to do and everything else rotates around it. That excites me about studying it, to figure out what it’s trying to do. It’s very, very cool to see it work.”
Also as part of the grant, Sarupria is developing new educational platforms aimed at teaching high school students, undergraduates and graduate students about materials engineering, computational materials science and working in multidisciplinary teams.
MuSiC Fest is a computational materials code fest mimicking popular hackathons. MolLego is a touchscreen game for high school and undergraduate students focused on molecular engineering.
Anand Gramopadhye, dean of the College of Engineering, Computing and Applied Sciences, congratulated Sarupria on the award.
“Dr. Sarupria shows excellence in research and education, making her CAREER award a richly deserved honor,” he said. “She exemplifies the role of teacher-scholar and the integration of the two.”
written by Paul Alongi, College of Engineering, Computing and Applied Sciences
