Synchronized forces behind flower-like patterns in plasma waves
Neither a solid, liquid, nor gas, plasma doesn’t play by the same rules as the other states of matter. Its unique properties are particularly evident at plasma-liquid interfaces, where chemical, electric and fluid forces collide to create waves.
In a recent paper in Physical Review Letters, engineers at the University of Notre Dame identify a new class of plasma-liquid waves that could be harnessed for multiple applications, from more effective water remediation technologies to gentler cancer treatments.
You throw a rock in a pond and you see ripples move outward because you’ve deformed the surface,” said Paul Rumbach, associate teaching professor in aerospace and mechanical engineering at the University of Notre Dame and co-author on the paper. “At the plasma-liquid interface, electrostatic force deforms the liquid, creating waves and motion.”
To produce these waves, the team ran electrical current through a needle-shaped electrode suspended above a petri dish of saline solution.
“You’d expect that the electrical current would generate just a single spot of plasma, like a flashlight beam on the surface,” said Rumbach. “But, if you turn up the voltage, that single spot turns into a ring, and, as you turn up the power higher, that ring breaks up into a pattern of spots that look like the petals on a flower.”
These floral plasma patterns often spin in a circle—a motion caused by the electrical interaction between the plasma and liquid.
When a liquid is flat, the pressure on it is evenly distributed, however, when the surface curves, the pressure changes. These unusual plasma-liquid waves form when pressure exerted by the plasma (Maxwell pressure) interacts with a liquid surface that has been curved by electrohydrodynamic forces. Plasma and liquid motions fall into sync, thus amplifying each other’s effects.
Motion is an important byproduct of this process. Currently, the water contaminant PFAS (per- and polyfluoroalkyl substances) can be destroyed by plasma, only if it happens to be on the micrometers-thin, plasma-liquid boundary. The team’s plasma-generated waves could mix the contaminated water, directing toxins toward the surface to be irradiated and pushing the by-products away.
“Plasma is a gentler, more efficient form of radiation that can be used to destroy contaminants in water or treat cancer,” said Rumbach. “Understanding how it interacts with water is critical for developing these applications.”
In addition to Rumbach, postdoctoral scholars Oles Dubrovski and Jinyu Yang at the University of Notre Dame contributed to this research, which was supported by the National Science Foundation, the Army Research Office, and the Notre Dame (ND) and Pontificia Universidad Católica de Chile (UC Chile) Scholars Joint Research Award.
Latest Research
- Through impactful partnerships, ND Mexico brings record number of undergraduate students to Notre Dame for research2024 iSTES students and staff celebrate new friendships and cherished memories at the program's Farewell Dinner.…
- ‘Show kindness and compassion’: In Fr. TED Talks, Notre Dame community explores what we owe each otherLast Monday and Tuesday evenings (Oct. 28 and 29), hundreds gathered under a tent on the Library Lawn to attend a Notre Dame Forum event titled “Fr. TED Talks: Ideas from the Catholic Social Tradition That We Find Inspiring.” The event featured a series of eight speakers from the Notre Dame community, culminating in a talk by University President Rev. Robert A. Dowd, C.S.C.
- Notre Dame and Purdue Engineers Use E-Textiles and Sensor Networks to Enhance Prosthetic FitAxel González Cornejo, doctoral student in Bolívar-Nieto’s lab (left), Prof. Bolívar-Nieto (center), and undergraduate mechanical engineering student, Sbeydi Ponce Duarte (right). The most common reason people with lower-limb loss stop using their prosthesis is an ill-fitting socket. Everyday activities such as standing, walking, or stair climbing put enormous pressures on the soft tissues of the residual limb, which are not well-adapted to managing the forces these activities generate. Engineers at the University of Notre Dame and Purdue University are collaborating to map the location and intensity of complex forces within prosthetic sockets. While previous studies relied on data collected by experts in laboratory settings, these researchers aim to develop a data-collection system that prosthetic users can wear comfortably during their daily activities. The data collected will enable researchers to design sockets better tailored to how users move.
- Notre Dame Law School’s Religious Liberty Clinic Provides Legal Support to Faith-Based NonprofitsStudents in Notre Dame Law School’s Lindsay and Matt Moroun Religious Liberty Clinic are providing invaluable legal support to religious nonprofit organizations through a section of the Clinic that specializes in transactional legal counseling. Offering…
- Rediscovering purpose: Justin’s journey from the football field to global explorationJustin at a viewpoint in Rio de Janeiro Justin Walters’ life seemed set in stone when…
- i-Lab Students Showcase Global Solutions in ActionStudents from the Masters of Global Affairs program at the Keough School of Global Affairs recently showcased their initial research findings during the 2024 i-Lab Global Partnership Experience.