Interfacial Phenomena: Samantha McBride’s Untapped Resource for Water Sustainability

Samantha McBride

In a typical year, Reno, Nevada, receives just seven and a half inches of rain. For Samantha McBride, the newest faculty member in Mechanical Engineering and Applied Mechanics, growing up in such an arid environment made clear the importance of water. “There’s a whole campaign for the Truckee River and Lake Tahoe,” she says. “People really take environmental challenges seriously because we have such limited water.”

As the William K. Gemmill Term Assistant Professor of Mechanical Engineering, McBride plans to probe the fascinating physics of interfacial phenomena, the world of interactions between two phases of matter, such as when a liquid meets a solid. “Many environmental challenges,” says McBride, “including desalination, boil down to interfacial processes.”

In desalination, the “interface” where these phenomena occur is a membrane, the pollution of which is known as “fouling.” Interfacial phenomena relate to virtually every aspect of water sustainability, from the persistence of microplastics in the water supply to new technologies to desalinate ocean water.

“Accumulation at the interface is a limiting factor in a lot of these processes,” says McBride. “I would love to come up with a technology that can change the face of water security, making sure we have clean water for everyone in the world at low cost without consuming too many nonrenewable resources.”

To that end, McBride’s lab brings together a range of scientific disciplines, including physics, chemistry and materials science. “My work is very multidisciplinary,” she says.

Penn Engineering’s emphasis on collaboration is what drew McBride to the School in the first place. “I’ve already had the chance to interact with professors from four different departments, the Penn Water Center and the Vagelos Institute for Energy Science and Technology,” she says.

Where most of us look at water and see a simple liquid, McBride is entranced by the complex mathematics that govern the interactions between water and particles suspended in it, from microplastics to minerals. “I think it’s very beautiful,” she says. “It’s like a puzzle.”

McBride’s work also produces incidentally artistic structures, like collections of crystals that resemble butterflies or AT-ATs, the walking quadrupedal robots from Star Wars, all of which she catalogs on her lab’s website.

A collection of mineral crystals that resembles a quadrupedal animal has been digitally edited to call to mind an AT-AT walker from Star Wars shooting lasers at an X-wing
A “Crystal Critter” reimagined as an AT-AT from Star Wars. (McBride Lab)

These crystals, which McBride has termed “Crystal Critters,” result from the evaporation of salty water on surfaces engineered to be extremely water-repellent, with boutique textures measured in billionths of a meter. Rather than require any sort of energy-intensive filtration through a membrane, these surfaces in effect force minerals to eject themselves and thereby prevent fouling at interfaces.

In the future, surfaces like these may reduce the need for desalinated water in power plants, which normally require thousands of gallons of fresh water to be turned into steam to spin turbines. (Using salt water would quickly gum up the turbines with mineral deposits.) “With engineered surfaces, perhaps we could take salt water,” McBride imagines, “use it as a working fluid, and then basically desalinate water as a byproduct of energy generation.”

This year, McBride will teach “Water Treatment Engineering,” a new course that will be the School’s first to focus exclusively on water technologies. “It is a master’s-level course,” she says, “but it’s also open to advanced undergraduates. Students are going to learn about a range of water processes for ocean water desalination, drinking water treatment, wastewater remediation and remediation of environmental pollution.”

In addition to hosting two undergraduate students and three master’s students, McBride is also looking to bring on several Ph.D. students this fall and looks forward to introducing more Penn Engineers to the possibility of applying their technical skills to improving the environment.

“One of the biggest impacts a lab like mine can have,” McBride says, “is through training students on environmental topics, and maybe motivating them to pursue environmental careers and having an impact of their own.”

To learn more about Samantha McBride and her research, please visit the McBride Lab’s website. In spring 2024, McBride is teaching MEAM 5620: Water Treatment Engineering. Students interested in joining the McBride Lab can learn more by visiting the McBride Lab’s website.