By Editorial Services
Research led by Sean Mills, assistant professor of materials science and engineering in Lehigh University’s P.C. Rossin College of Engineering and Applied Science, has received the 2025 Outstanding Paper Award in Materials Science from Microscopy and Microanalysis.
Mills is the lead author of the paper “Tiny Bubbles: Combined HR(S)TEM and 4D-STEM Analysis of Sub-Nanometer He Bubbles in Au,” published in the journal in August 2025. The award was presented during the plenary session of the Microscopy & Microanalysis 2026 meeting, held August 2-6 in Milwaukee.
The study combines atomic-scale high-resolution scanning transmission electron microscopy (HRSTEM) and four-dimensional scanning transmission electron microscopy (4D-STEM) to characterize helium bubbles and other irradiation-induced nanoscale point defects in gold.
Helium bubbles are among the defects that form in metals exposed to radiation and can affect how structural materials behave under prolonged exposure to harsh nuclear reactor environments. Because the smallest bubbles approach the scale of unit cells, the smallest repeating atomic arrangements in a crystal system, they are exceptionally difficult to characterize using conventional imaging techniques. This novel STEM-based approach enabled researchers to directly image these sub-nanometer bubbles while mapping their distribution and local strain fields in the surrounding material.
The research was conducted through the Fundamental Understanding of Transport Under Reactor Extremes (FUTURE), an Energy Frontier Research Center funded by the U.S. Department of Energy’s Office of Basic Energy Sciences. The center brings together researchers studying structural materials under extreme conditions, including irradiation, high temperatures, and corrosion.
The publication represents a collaborative effort among researchers from the University of California, Berkeley; Lawrence Berkeley National Laboratory; Los Alamos National Laboratory; the University of Tennessee; and the Austrian Academy of Sciences. Mills performed the primary research while he was a postdoctoral researcher at UC Berkeley and an affiliate of the National Center for Electron Microscopy at Berkeley Lab.
Mills joined Lehigh’s faculty in August 2025 and continues to collaborate with FUTURE at Lehigh. His lab implements advanced high-resolution electron microscopy techniques to characterize and inform the design of structural metal alloys capable of withstanding harsh operating environments.
“It’s exciting to see this work recognized, particularly because it reflects the collaborative nature of FUTURE and the range of expertise that went into the study,” Mills says. “I’m looking forward to continuing those collaborations and expanding Lehigh’s involvement in the center’s ongoing research.”