With some strains of bacteria becoming increasingly resistant to antibiotics, contamination by touching infected surfaces or coming into contact with airborne microbes is fast becoming a real threat to public health. Hand-sanitizer liquids and masks may go some way toward reducing this problem, but clothes, equipment, and other items can all harbor disease and are not readily cleanable with standard chemicals or methods. To help address this situation, scientists at Rutgers University have come up with a way to produce paper-based plasma generators. These could be worn on clothing or fitted to equipment, to zap any bug they come into contact with cheaply and easily.
Already high-tech sensors are able to detect the presence of harmful E. coli bacteria, and devices that can kill them with solar power or even fry them on the spot with a combination of gold nanodisks and lasers. However, as capable as these methods may be, their cost, complexity, and limited effectiveness on large surface areas reduces their practical deployment on a large scale. Paper-based sanitizers, on the other hand, could be cheap and flexible enough to be suitable for incorporation in clothing that sterilizes itself, devices that automatically sanitize laboratory equipment, or even electronic bandages that help heal wounds better by keeping out infection altogether.
Motivated by the likes of the outbreak of Ebola in West Africa, the Rutgers scientists sought to produce active protective appliances and methods to minimize the spread of infectious diseases that were both inexpensive and easy to produce. The research resulted in an electronic disinfectant material made of paper coated with thin layers of aluminum honeycomb patterns that act as electrodes to produce the plasma. Plasma, or ionized gas, is formed when a high-voltage charge ionizes a gas, in this case ordinary air, so that electrons are torn from their atoms. This results in a high-energy field of electrons and ions that, in this case, is used to vaporize any bacteria that comes into contact with it.
Whilst paper may seem a counter-intuitive choice for such a device, its intrinsic fibrous nature and porous interior actually provides a large area through which gas may permeate. This, in turn, helps keep the the plasma fuelled whilst keeping the whole system adequately cooled.
"Paper is an ancient material, but it has unique attributes for new, high-tech applications," said Aaron Mazzeo, assistant professor in the Department of Mechanical and Aerospace Engineering at Rutgers University. "We found that by applying high voltage to stacked sheets of metallized paper, we were able to generate plasma, which is a combination of heat, ultraviolet radiation and ozone that kill microbes."
Experiments conducted by the team at Rutgers showed that their paper devices wiped out more than 99 percent of a yeast microbe known as Saccharomyces cerevisiae, and killed more than 99.9 percent of E. coli bacteria cells. Though E. coli bacteria is one of the most prolific species of microbes on the planet, most strains are harmless and many contribute to the health of the human gut. The nasty types, such as the ones that can cause diarrhea, pneumonia, infections of the urinary tract, and other debilitating or life-threatening illnesses, are the ones that we require protection from. In particular, we need a safe way to both halt these microbes in their tracks and stop them spreading.
"Preliminary results showed that our sanitizers can kill spores from bacteria, which are hard to kill using conventional sterilization methods," said Qiang (Richard) Chen, a doctoral candidate in the Department of Plant Biology in Rutgers' School of Environmental and Biological Sciences.
"Our next phase is to vigorously test how effective our sanitizer system is in killing spores," continued James F. White Jr., professor of plant pathology in the Department of Plant Biology at Rutgers.
Ongoing research at Rutgers aims to produce devices that mimic the way skin protects us from microbes and bacteria outside the body, while detecting the inputs of touch, pressure, temperature, and moisture. According to the scientists, these detectors may be formed into covers for prosthetics, parts of buildings, or the surfaces of vehicles, making it possible to sterilize machinery, robots, or pieces of equipment before they go into contaminated areas and again when they come out. Similarly, surfaces in buildings could be constantly cycled with plasma cleaning to kill any microbes that land on them.
The results of this study were recently published in the journal Proceedings of the National Academy of Sciences of the United States of America.
The video below details more of the research and construction of the metallized paper plasma generators by the Rutgers University team.
Source: Rutgers University
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