‘Emerging Investigators’ are Studying Flow of Soft Materials through Tiny Spaces
ChE Assistant Professor Sara Hashmi has been recognized in the “Emerging Investigators” series of the Royal Society of Chemistry journal Soft Matter. First author is Barrett Smith, PhD’24, chemical engineering. Their paper, “In Situ Polymer Gelation in Confined Flow Controls Intermittent Dynamics” uncovers novel flow behavior in crosslinking biopolymers.
The Hashmi Complex Fluids Lab studies soft materials flowing through small spaces. These phenomena are important in many contexts, ranging from particle flows through the earth’s porous subsurface to microfluidic droplet-based PCR test assays. In blood, the situation is even more complicated as blood proteins can both polymerize and crosslink together in a flow. When this happens to fibrinogen, the resulting fibrin mat sticks to the vessel wall, forming a clot. Blood clots, of course, can have deadly implications. In their paper, they set out to understand what happens in a much simpler system. As it turns out, extremely rich dynamics emerge even with two components flowing through a microfluidic channel: an alginate polymer and a calcium crosslinker. The polymer crosslinks sticks to the wall, and then eventually grows so large that the fluid flowing by can pull it off, leaving a clean channel. Even more remarkable: this gelation, deposition, and ablation process repeats seemingly indefinitely when the chemistry is right. While the Soft Matter article explores the wide range of conditions that lead to this behavior, Smith and Hashmi are working on a subsequent manuscript using theoretical models to describe and explain it further. The research is funded by Hashmi’s NSF CAREER Award.