NSF CAREER Award for Examining Flow of Polymer Gels in Confined Spaces
ChE Assistant Professor Sara Hashmi was awarded a $550K NSF CAREER award for “In situ Polymer Gelation in Confined Flows” to examine how polymer gels flow through tight spaces to better predict clogging behavior such as blood flow through a vessel.
Sara Hashmi, assistant professor of chemical engineering, received a $550,000 National Science Foundation (NSF) CAREER Award for “in situ Polymer Gelation in Confined Flows” to examine how polymer gels flow through tight spaces to better predict clogging behavior. Polymer gels are all around us in both natural and industrial settings, including gelatin, toothpaste, 3D printing materials—even human blood.
“The idea of blood clotting within a blood vessel is the real-world problem that originally inspired me to think about this research,” says Hashmi. “What happens in the blood is very complicated, but in the final stages when the molecules become a polymer, they can stick together and to the walls of the blood vessel and cause problems. We want to better understand the fundamental science of how crosslinked polymers flow through small channels—as can happen in blood flow through a vessel—so we can potentially prevent or reverse clogging in many different applications.”
For this research, Hashmi and Barrett Smith, a chemical engineering graduate student in her Complex Fluids Lab, have built a microscopic channel with two inlets on one end. They inject alginate, a naturally occurring polymer, through one opening and calcium chloride in the other; when the two combine, they crosslink, or begin to get stuck together and to the walls of the channel. Hashmi and Smith then record and observe this microscopic behavior within their model.
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Barrett Smith, chemical engineering graduate student, and Sara Hashmi, assistant professor of chemical engineering, record and observe microscopic behavior of crosslinked polymer gels within their research model. They built a microscopic channel with two inlets on one end. They inject alginate, a naturally occurring polymer, through one opening and calcium chloride in the other; when the two combine, they crosslink, or begin to get stuck together and to the walls of the channel.
By manipulating variables, such as the amount of alginate versus calcium chloride or the speed at which they are injected, Hashmi and Smith are gaining insight into the behavior of these polymers. Of particular interest to the two is the intermittent behavior that occurs in a realm between steady flow and complete clogging.
“One of the interesting things we observe when clogs begin to form is that, as the channel becomes narrower and the fluid speeds up to go through that smaller space, the forces start to disrupt the gel, breaking off very small, very soft particles,” says Hashmi. “Really tiny and soft gels are difficult to make in practice because they’re very fragile, but this brings us into a thought-provoking future direction: How is this product that we’re making useful, and can we make it consistently reproduceable?”
By creating mathematical models to better understand the physical processes of these flow patterns, Hashmi’s research can extend into a range of applications, from pharmaceutical and biomedical to industrial. As part of her research, she intends to engage colleagues in additive manufacturing and other fields to help answer industry-specific questions that are yet unknown.
“People who study 3D printing generally publish about their successes, but we want to learn more about the failures,” says Hashmi. “What have people tried to avoid or reverse clogging that hasn’t worked? By developing a survey for academic and industry colleagues, we can learn more about real-world needs to help us determine what models and systems we should explore next.”
As part of the CAREER grant, Hashmi is also engaging in STEM education opportunities for teachers and students in the Greater Boston area.
“We want to create a summer workshop to collaborate with Boston Public School teachers on publishable curriculum development for high school science classes,” says Hashmi, who is partnering with Northeastern’s Center for STEM Education on this effort. “Because high school science curriculum doesn’t typically have much engineering content, we have a lot of opportunity to bring in fundamental concepts around complex fluids because they are so ubiquitous.”
With Boston’s diverse school population, Hashmi and her team will be working to bring more access to these engineering concepts to communities who are historically underrepresented in STEM.