Yuexiao Shen has led a study revealing the 3D nanostructure of reverse osmosis membranes in their hydrated state.
Yuexiao Shen, an assistant professor from the Department of Civil, Environmental & Construction Engineering in the Edward E. Whitacre Jr. College of Engineering has led a groundbreaking study revealing, for the first time, the 3D nanostructure of reverse osmosis membranes in their hydrated state — a major advancement for global water treatment technologies.
Shen directed a collaborative team that used cryo-electron tomography to visualize the nanoscale structure of reverse osmosis (RO) membranes under conditions that mimic real-world water treatment environments. Their findings were recently published in the journal Science Advances.
“For decades, the internal hydrated structure of RO membranes has remained largely a mystery,” Shen said. “We’re finally getting closer to understanding what happens at the water-membrane interface and how nanoscale morphology contributes to water and solute transport.”
RO membranes are widely used in both large municipal water treatment systems and compact residential filtration devices. Though they’ve been critical for global water purification for more than 50 years, the selective layer — just 100 to 200 nanometers thick — has defied full structural analysis due to its complexity and the technical challenges of imaging hydrated polymers.
Shen, a pioneer in membrane tomography, began his research in 3D membrane structure as a lead author in a 2018 PNAS publication. Since joining Texas Tech, he has advanced algorithm development for post-processing tomography data Environmental Science & Technology Engineering and co-authored a comprehensive review in Environmental Science & Technology.
To achieve this latest breakthrough, Shen collaborated with Menachem Elimelech of Rice University and Huang Xia of Tsinghua University. Over four years, the team adapted cryo-electron tomography — typically used in biological imaging — to study polymeric materials in their hydrated form.
The results revealed detailed hydrated nodular networks inside the membranes. The 3D models showed that water and salt transport primarily occur through these nodules, which are formed by nanobubbles during membrane fabrication. Developed nodules had thin walls measuring 17.2±2.8 nanometers, while membranes with underdeveloped nodules showed denser layers nearly four times as thick.
The study also found a direct link between water permeability and membrane nanostructure, offering new insights into how these materials can be engineered for better performance.
“This work not only solves a longstanding scientific challenge, but it also opens new pathways for improving desalination membranes to address global water scarcity,” Shen said.