Novel coronavirus and its effect on University science laboratories has kept engineering student Portia Tieze from working on campus this summer — so she brought the lab to her apartment to continue her research.
Over the course of this summer, rising Brown junior Portia Tieze has designed and performed complex experiments aimed at better understanding how microorganisms are able to achieve remarkable feats of swimming prowess. Under normal circumstances, these kinds of experiments would take place in a state-of-the-art science lab on the Brown campus. But this has been no ordinary summer.
With University research laboratories operating at reduced capacity due to the COVID-19 pandemic, working inside the lab this summer wasn’t an option for Tieze. So with the help of Brown engineering professor Roberto Zenit, Tieze moved the lab — part of it anyway — into her apartment near campus in Providence.
“I guess it’s probably not that unusual for an engineering student to have a little bit of random research stuff in their apartment,” Tieze said. “But to have an oscilloscope, Helmholtz coils and a power supply set up in a bedroom, that’s a little different. One of the funny stories from all of this is that one day I was walking down Thayer Street with the oscilloscope and people were saying, ‘What is that? Are you a mad scientist?’”
The characterization didn’t bother Tieze at all. The Colorado native has been interested in science since primary school.
“I was fortunate enough to have spent a lot of time exploring the Rocky Mountains as a kid,” she said. “I grew to love how science entertained the questions that my adventures inevitably spurred within me. What’s this rock made of? How do the stars look like that? How is this moss living?”
The question she’s tackling this summer is about how microscopic swimmers — bacteria, sperm cells and other microorganisms — are able to move around. Macroscale creatures like fish and humans are able to swim through water and similar liquids with ease. But imagine if that water were something more like maple syrup. Plowing through it wouldn’t be so easy, and that’s the situation in which microorganisms find themselves.
One of Tieze's swimmers makes its way across a vat of corn syrup.
At the micro scale, viscous forces are much larger, yet microorganisms are able to move around with apparent ease. Understanding how they do it could shed light on everything from how infections spread through the body to how to design tiny swimming robots.
“My specialty is in fluid mechanics, and I’m interested in how the properties of fluids affect swimming behavior,” said Zenit, who is overseeing Tieze’s work via Zoom videoconferencing and worked with her on the appropriate equipment setup. “It’s hard to work with actual bacteria because they’re so small. So we cheat. We scale everything up and increase the viscosity of the fluid accordingly. Now we have a model where we can change different parameters of the in the experiment to find out which ones are important.”
For her experiments, Tieze has made pill-sized plastic swimmers, each equipped with a rare-earth magnet. The swimmers are placed in a small vat of viscous fluid, corn syrup in this case. The vat is surround by a Helmholtz coil — a pair of powerful electromagnets that create a magnetic field. Switching the orientation of the magnetic field back and forth causes the magnetic swimmers to wiggle in a way that mimics microscale swimming. The oscilloscope measures the amount of current flowing through the coils, which reveals the forces involved in the swimming motion.
Much of the work Tieze has done to date has been setting up the apparatus, preparing the swimmers and getting the whole set-up to work properly. It’s been a challenge at times doing this remotely rather than in the lab, Tieze and Zenit say. But they’re making it work.
An oscilloscope measures the forces exerted by the little swimmers.
“We’ve sort of become Zoom experts,” Zenit said. “Sometimes Portia uses both her computer and her phone on Zoom at the same time so we can talk and get a close look at what she’s doing. It’s been kind of fun, actually.”
With the setup fully functional, Tieze can perform a variety of swimming experiments. For example, she can alter attributes of the swimmers’ tails to untangle how length, thickness and rigidity affect swimming forces. The results could reveal new fundamental insights into microscale swimming. The work could also earn Tieze authorship on a peer-reviewed journal paper — a major boon for any undergraduate researcher considering graduate school.
Tieze says the project has been full of little reminders of why she fell in love with science in the first place. She had to use precise calculations, for example, to design the swimmers to be neutrally buoyant — able to be suspended in the liquid without sinking or floating to the top.
“That’s one of my favorite things about physics,” said Tieze, who is concentrating in mechanical engineering. “You do the math, follow what it tells you to do — and it actually works!”
“Working with Professor Zenit this summer has reaffirmed what I first understood to be the beauty of science,” she added. “With a bit of math and a bit of creativity, we have the power to ask and seek out answers to any question imaginable.”