Microplasma Research in the Small Scale Transport Lab
Whether or not we fully realize it, our lives are greatly influenced by advancements that take place on the scale of micrometers and nanometers—at the level of ions and neutral particles in microplasmas, specifically low-temperature plasmas. For example, the energy-efficient compact fluorescent (CFL) light bulb is a plasma device used in most households, and plasma-based materials processing has been essential to computer chips in the consumer electronics industry. Plasma research and engineering has the potential to address challenging energy problems, offer new water purification methods, create new nanomaterials for specialized applications, and convert captured waste heat directly into electricity; greatly improving quality of life. These topics are just a sample of the range of diverse research actively under way in the Small Scale Transport (SST) Research Lab at Notre Dame, directed by David Go, assistant professor of aerospace and mechanical engineering.
Go and his group study the transport of energy, fluids, and charge at scales from millimeters all the way down to nanometers with his research ranging from understanding basic phenomena to technology development for a wide variety of applications. While projects include microfluidics and sprays for chemical analysis, as well as energy and heat transfer topics, plasma science and engineering is central to the various paths the research follows. Go views his plasma research as “attempting to understand the generation and fate of electrons and ions in novel plasma systems in order to optimize these systems for targeted applications.”
Researchers in the SST Lab push the boundaries of what is currently known about low-temperature plasmas, seeking new insights and a deeper understanding of what is taking place at the physiochemical level. They aim to understand how electrons are produced and what happens to them. This knowledge will provide clues regarding how to control the electron processes for specific applications.
Microplasmas, a specific class of low-temperature plasmas operated at micrometer scales, are unique because they can operate at atmospheric pressure. Thus, microplasmas are able to interact with liquids, plastics, tissues, and other surfaces that cannot be put into a vacuum. Studying the fundamental science, particularly how microplasma electrons interface with liquids, adds to the body of knowledge and creates opportunities for new applications. Some of these emerging applications include purifying water, treating open wounds, sterilizing surfaces, and biosensing. Currently, Go and his team are focusing on how electrons from the microplasma can be used to drive electrochemical reactions in liquids in work that involves synthesizing and patterning nanoparticles for use in biological sensing and other applications.
The high current that can be produced by controlling the discharge of electrons from a surface into a microplasma is also being used by researchers to develop new electron-driven devices. One of the specific applications being explored involves using microplasmas to enhance the conversion of heat directly into electricity by way of thermionic energy conversion, a process that addresses energy issues on the ground and in space technology. Heat from the sun, nuclear energy, or waste heat from power plants is used to heat materials that “emit” electrons into a microplasma where it increases conversion efficiency. In another application Go’s group is studying, electrons injected into a plasma can enhance catalytic reactions; in particular, microplasmas are being used in converting natural gas (methane) into hydrogen for use in fuel cells and other energy applications.
Many more innovative topics are explored in the SST research lab as well. According to Go, he and his group “ask interesting questions then go and find or develop the tools to answer those questions, which ultimately will lead to new discoveries and new technologies.”