Dr. Gabe Xu, a professor in the Mechanical and Aerospace Engineering Department at The University of Alabama in Huntsville (UAH).
Imagining a college dorm room as an enclosed environment for weeks on end instantly points to the motivation behind the need for an effective means of sanitizing surfaces and clothes, particularly as longer crewed missions become a reality. Researchers at The University of Alabama in Huntsville (UAH), a part of The University of Alabama System, are developing plasma-based technology to help astronauts stay healthier during missions to the moon and Mars by sanitizing clothing, bedding and other fabrics without water or traditional cleaning chemicals. The researchers have devised a special “laundry gun” that blasts cold plasma into fabrics to reduce harmful bacteria during long-duration spaceflight, lessening the need for water-intensive laundry, while maintaining cleaner living quarters, spacesuits and equipment.
Conducting plasma research in the Gabe Xu Lab on the UAH campus.
Led by Dr. Gabe Xu, a professor of mechanical and aerospace engineering at UAH, the effort is a collaboration with NASA's Marshall Space Flight Center (MSFC).
“The purpose of the laundry gun is to sanitize soft material, such as fabrics on couches, bedding, clothes, etc. in enclosed space habitats like the International Space Station or on lunar and Mars expeditions,” Xu explains. “This will reduce the microbial load and keep clothes and other soft surfaces clean, at least microbially, for astronaut health. It could also be used to sterilize space suits and tools before they leave the habitat and step foot on Mars. To be clear, though, this won't remove coffee or grass stains (though we haven't tried that). So, it won't make your clothes less dirty, just remove bacteria.”
Instead of relying on detergents or disinfectants, the lab prototype generates plasma from helium, air and water vapor. The charged particles that are produced create reactive oxygen species that destroy bacteria by damaging their cell membranes. “Species” refers to a specific chemical form – such as a molecule, ion or radical – that drives chemical reactions, including the reactive compounds responsible for oxidation, a process that can break down, destroy or transform target substances like pollutants or bacteria by chemically attacking them.
“The plasma is made of positively charged ions and energetic free electrons,” Xu notes. “The electrons in particular collide with other gas molecules such as H2O and O2 to create reactive oxygen species such as O3 and OH. These species are biologically active, meaning cells can absorb them and then affect cell components. For example, bacteria have lipid membranes which can be oxidized by these species, leading to membrane damage and cell death. Oxidation of the cell membrane is how other antimicrobial methods work as well, like peroxide and parts of bleach. But, with the plasma, we can directly generate the necessary oxidizing species from air and/or water vapor.”
The project grew from efforts to improve planetary protection by sanitizing spacesuits and tools before they are used on other worlds. Researchers soon recognized the broader challenge of maintaining clean, comfortable habitats during months-long missions where water is limited and conventional cleaning chemicals are unsuitable for enclosed environments.
“This experiment has been a partnership between my lab at UAH and Dr. Chelsi Cassilly at NASA MSFC,” Xu says. "We have been looking at plasma for sanitization for planetary protection for a couple of years with UAH providing the plasma science and engineering. Plasma can contribute not only to planetary protection for killing bacteria, but also for increased growth of plants for space agriculture and breakdown of waste for waste processing for human space flight."
While the concept has shown promise in laboratory testing, significant engineering work remains before it is ready for spaceflight. Researchers are now designing a larger handheld device capable of treating broader fabric surfaces while safely removing ozone produced during the sanitization process.
“The use of plasma treatment could significantly reduce the mass of goods needed for a human mission, especially one to Mars where resupply is difficult,” Xu points out. “With just electricity, air, water and perhaps other gases, the plasma could help tackle sanitization, space crops, water purification, air revitalization, waste processing and even regolith treatment [lunar or Martian soil]. Of course, those applications are also in the early stages and focused efforts will be needed to bring this technology to flight."
Beyond fabric sanitization, Xu's research highlights the versatility of plasma technology as NASA looks toward sustained human exploration beyond low Earth orbit. Future applications could include supporting life-support systems, improving space agriculture, processing waste and helping astronauts live and work more safely on the lunar surface and Mars.