New research published in Physical Review Research reveals important fundamental insights into superparamagnetic colloids. These super small magnetic microbeads each measure in at a hundred times smaller than the diameter of a grain of sand. Evelyn Tang, assistant professor of physics and astronomy, and Sibani Lisa Biswal, the William M. McCardell Professor in Chemical Engineering, have made surprising discoveries together. Their groundbreaking study of particles has revealed a previously hidden law of nature.
The research team, including former postdoc Aleksandra Nelson and recent graduate Dana Lobmeyer, isolated superparamagnetic colloids in a saline solution. They were interested in probing the amazing emergent collective behavior of these particles. The particles were unusual in that they easily and reversibly formed clusters that would reshape themselves and combine with other clusters in mere minutes. In comparison, sheets with voids required much longer to change shape.
Evelyn Tang, who studied this impressive phenomenon — the fact that particles on clusters could all rotate in unison, like dancers performing in perfect synchrony — wrote her response. She was excited when the first data started coming in. It proved to be a powerful demonstration that streams of particles were traveling faster along the edges than the center.
“When I saw the initial data—with streams of particles moving faster along the edges than in the middle—I said ‘these are edge flows’ and we got to work exploring this,” – Evelyn Tang
These findings from the study indicate that the appearance of these edge flows can be understood using ideas from topological physics. Tang focused on the human side of this relationship, saying,
“What’s very exciting is that we can explain their emergence using ideas from topological physics, a field that became prominent due to quantum computers and [exotic materials].”
she commented on the larger effects of their work, claiming,
“We’re taking a concept from fundamental math and [statistical physics] to apply it to everyday materials. It’s a reminder that the same elegant rules can show up right in the lab next door.”
Sibani Lisa Biswal, one of the researchers, emphasized the significance of topology in her research. She likened it to traffic signs that direct flow patterns. This metaphor emphasizes that the more we know about these principles, the easier it is for innovators to develop new ways to guide material behavior.
Our research team has spent years exploring superparamagnetic colloids. Their exploration increases our understanding of particle dynamics and opens up new possibilities for future studies into material science. As such, Evelyn Tang was perfectly positioned to serve as the corresponding author for this pivotal first study, easily referenced with its DOI 10.1103/PhysRevResearch.7.023094.
“We’re learning how to control collective behavior using simple physical principles.”
The research team’s exploration of superparamagnetic colloids not only enhances understanding of particle dynamics but also opens avenues for future studies in material science. Evelyn Tang served as the corresponding author for this pivotal study, which can be referenced with the DOI 10.1103/PhysRevResearch.7.023094.