Kathleen Stebe, the Goodwin Professor of Applied Science and Engineering at the University of Pennsylvania, presented the prestigious 2024 Julian C. Smith Lecture hosted by the Smith School. Stebe, a soft matter and complex fluids expert, delivered two thought-provoking talks over the course of the annual two-day lecture series.
The first lecture, titled “Peptide Surfactants (PEPS) for the Green Separation of Rare Earth Elements,” delved into an innovative and environmentally friendly method for separating rare earth elements essential for modern technologies. The Stebe Lab is developing functional peptide surfactants (PEPS) to tackle this issue. Traditionally, rare earth elements are separated through liquid-liquid extraction, a method that uses oil-soluble chemicals to bind with rare earths and transfer them to an organic phase. Stebe’s research focuses on creating ‘green’ peptide surfactants that bind selectively to rare earths, enabling a more efficient and environmentally friendly separation process.
These PEPS complexes attach to the air-water interface, where they can be recovered through a froth flotation process. This approach could revolutionize how rare earth elements are separated, offering a sustainable alternative that reduces the ecological impact of current extraction processes.
The second lecture, “Defect Propelled Swimming and Interactions of Nematic Colloids for Microrobotics,” explored the world of microrobotics through the lens of nematic liquid crystals – highly non-linear fluids with unique elastic properties that resist molecular rearrangement, creating high-energy defect sites. Stebe’s research investigates how these defects can be harnessed to propel microscopic particles, specifically ferromagnetic disk colloids, through liquid crystal environments. By rotating the colloids with an in-plane magnetic field, Stebe and her team observed how the colloids’ anisotropic defect structures and the Nematic liquid crystal’s elastic response generated a swimming motion. This discovery opens new possibilities for controlling microrobotic movement in low Reynolds number environments, where conventional swimming mechanisms do not apply. The study of nematic colloids also reveals a toolkit for manipulating colloidal interactions, offering a platform for creating reconfigurable materials that could transform fields ranging from material science to medicine.
Stebe is a highly accomplished researcher in the field of chemical engineering. She earned her B.A. in economics from the City College of New York, graduating magna cum laude. She later completed her Ph.D. in chemical engineering at the Levich Institute. After a postdoctoral year in Compiegne, France, and prior to joining the University of Pennsylvania, she was a faculty member at the Department of Chemical Engineering at Johns Hopkins University, where she eventually became department chair.
The Julian C. Smith Lecture series was established by the class of 1962, along with other colleagues and friends, to honor Professor Julian C. Smith for his invaluable contributions to academic research and his tenure as director of the school from 1965 to 1981.