Scientists find the best DIY face mask design and materials

Combining two fabrics is the best way to filter out infectious coronavirus particles according to a new study.

Photo Credit: ti-ja / Getty Image
  • Researchers found that combining two materials in a "hybrid" mask is the best alternative method to stop the spread of coronavirus.
  • The filtration efficiency of the hybrid materials such as cotton-silk, cotton-chiffon, and cotton-flannel was greater than 80 percent for particles less than 1000 nanometers.
  • The most important thing is to ensure that your mask fits properly and that you wear it correctly.

Though there is some debate, most medical experts agree that wearing a mask in public to stop the spread of COVID-19 is better than doing nothing.

As to what kind of design is most effective, research published in ACS Nano found that combining two materials is the best method to stop the spread of infection. But the fit must be right.

Materials tested

medical face mask

Photo Credit: De an Sun / Unsplash

Because surgical and N95 masks are scarce and should be reserved for medical professionals only, you should be either purchasing or making cloth facial coverings.

Researchers from Argonne National Laboratory and the University of Chicago in the United States tested which materials were the most effective at filtering out germ ridden particles. They took a variety of common materials including cotton, silk, chiffon, flannel, various synthetics, and combinations of each to investigate the mechanical and electrostatic filtration properties in lab conditions.

The scientists found that mixing a variety of fabrics and applying multiple layers was the best way to filter out particles. However, it is essential that the mask fits properly or else the entire contraption is a bust.

"Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles," explain the researchers in their paper.

Experimental design

Fig. 1- Schematic of the experimental setup. A polydisperse NaCl aerosol is introduced into the mixing chamber, where it is mixed and passed through the material being tested ("test specimen")

Abhiteja Konda et. al.

To conduct this test, the researchers sampled the number of aerosol particles in the air by using an aerosol mixing chamber. Next, they filtered the particles through each of the test fabrics, which were secured on the end of a PVC tube. They then sampled the air that made it through that material.

The particle sizes in the experiment varied wildly, from about 10 nanometers up to 10 micrometers. (One micrometer equals 1000 nanometers.) Coronavirus particles range between 80 and 120 nanometers in diameter.

The particles tested were small, and we don't yet know if those little aerosolized particles can cause disease. However, materials that can filter out even the smallest of particles are the best bet to ensure that the larger particles, more likely to carry infection, will be denied entry.

Hybrid masks are best

Abhiteja Konda et. al.

The team found that layering multiple materials ('hybrid' fabrics) was the best approach to filtering out a majority of particles.

The filtration efficiency of the hybrid materials such as cotton-silk, cotton-chiffon, and cotton-flannel was greater than 80 percent for particles less than 1000 nanometers. It was greater than 90 percent for particles greater than 300 nanometers. Simply put, those combinations were very effective at keeping particles from transmitting.

"We speculate that the enhanced performance of the hybrids is likely due to the combined effect of mechanical and electrostatic-based filtration," noted the researchers.

The team found that fabrics like cotton, which has a high thread count, work the best at catching particles (called 'mechanical filtration'). Smaller gaps mean that fewer big particles can shimmy through.

"Electrostatic-based filtration is a little different," reports Science News. "Think of a super static-y material such as polyester. Instead of zapping a friend with all the static electricity you saved up, the electrostatic filter keeps the aerosols inside the static environment."

A proper mask fit is essential

But the most important thing is to ensure that your mask fits properly, and that you wear in correctly. In the second part of the experiment the team poked tiny holes in the fabrics they were experimenting on, and the results were alarming.

"Our studies also imply that gaps (as caused by an improper fit of the mask) can result in over a 60 percent decrease in the filtration efficiency," the researchers explained.

You can make a hybrid material mask using several online resources. Or, if you just want to make an old school mono-material mask, that's better than nothing. The CDC has a guide here.

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Sponsored by Charles Koch Foundation
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The surprise reason sleep-deprivation kills lies in the gut

New research establishes an unexpected connection.

Reactive oxygen species (ROS) accumulate in the gut of sleep-deprived fruit flies, one (left), seven (center) and ten (right) days without sleep.

Image source: Vaccaro et al, 2020/Harvard Medical School
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  • A study provides further confirmation that a prolonged lack of sleep can result in early mortality.
  • Surprisingly, the direct cause seems to be a buildup of Reactive Oxygen Species in the gut produced by sleeplessness.
  • When the buildup is neutralized, a normal lifespan is restored.

We don't have to tell you what it feels like when you don't get enough sleep. A night or two of that can be miserable; long-term sleeplessness is out-and-out debilitating. Though we know from personal experience that we need sleep — our cognitive, metabolic, cardiovascular, and immune functioning depend on it — a lack of it does more than just make you feel like you want to die. It can actually kill you, according to study of rats published in 1989. But why?

A new study answers that question, and in an unexpected way. It appears that the sleeplessness/death connection has nothing to do with the brain or nervous system as many have assumed — it happens in your gut. Equally amazing, the study's authors were able to reverse the ill effects with antioxidants.

The study, from researchers at Harvard Medical School (HMS), is published in the journal Cell.

An unexpected culprit

The new research examines the mechanisms at play in sleep-deprived fruit flies and in mice — long-term sleep-deprivation experiments with humans are considered ethically iffy.

What the scientists found is that death from sleep deprivation is always preceded by a buildup of Reactive Oxygen Species (ROS) in the gut. These are not, as their name implies, living organisms. ROS are reactive molecules that are part of the immune system's response to invading microbes, and recent research suggests they're paradoxically key players in normal cell signal transduction and cell cycling as well. However, having an excess of ROS leads to oxidative stress, which is linked to "macromolecular damage and is implicated in various disease states such as atherosclerosis, diabetes, cancer, neurodegeneration, and aging." To prevent this, cellular defenses typically maintain a balance between ROS production and removal.

"We took an unbiased approach and searched throughout the body for indicators of damage from sleep deprivation," says senior study author Dragana Rogulja, admitting, "We were surprised to find it was the gut that plays a key role in causing death." The accumulation occurred in both sleep-deprived fruit flies and mice.

"Even more surprising," Rogulja recalls, "we found that premature death could be prevented. Each morning, we would all gather around to look at the flies, with disbelief to be honest. What we saw is that every time we could neutralize ROS in the gut, we could rescue the flies." Fruit flies given any of 11 antioxidant compounds — including melatonin, lipoic acid and NAD — that neutralize ROS buildups remained active and lived a normal length of time in spite of sleep deprivation. (The researchers note that these antioxidants did not extend the lifespans of non-sleep deprived control subjects.)

fly with thought bubble that says "What? I'm awake!"

Image source: Tomasz Klejdysz/Shutterstock/Big Think

The experiments

The study's tests were managed by co-first authors Alexandra Vaccaro and Yosef Kaplan Dor, both research fellows at HMS.

You may wonder how you compel a fruit fly to sleep, or for that matter, how you keep one awake. The researchers ascertained that fruit flies doze off in response to being shaken, and thus were the control subjects induced to snooze in their individual, warmed tubes. Each subject occupied its own 29 °C (84F) tube.

For their sleepless cohort, fruit flies were genetically manipulated to express a heat-sensitive protein in specific neurons. These neurons are known to suppress sleep, and did so — the fruit flies' activity levels, or lack thereof, were tracked using infrared beams.

Starting at Day 10 of sleep deprivation, fruit flies began dying, with all of them dead by Day 20. Control flies lived up to 40 days.

The scientists sought out markers that would indicate cell damage in their sleepless subjects. They saw no difference in brain tissue and elsewhere between the well-rested and sleep-deprived fruit flies, with the exception of one fruit fly.

However, in the guts of sleep-deprived fruit flies was a massive accumulation of ROS, which peaked around Day 10. Says Vaccaro, "We found that sleep-deprived flies were dying at the same pace, every time, and when we looked at markers of cell damage and death, the one tissue that really stood out was the gut." She adds, "I remember when we did the first experiment, you could immediately tell under the microscope that there was a striking difference. That almost never happens in lab research."

The experiments were repeated with mice who were gently kept awake for five days. Again, ROS built up over time in their small and large intestines but nowhere else.

As noted above, the administering of antioxidants alleviated the effect of the ROS buildup. In addition, flies that were modified to overproduce gut antioxidant enzymes were found to be immune to the damaging effects of sleep deprivation.

The research leaves some important questions unanswered. Says Kaplan Dor, "We still don't know why sleep loss causes ROS accumulation in the gut, and why this is lethal." He hypothesizes, "Sleep deprivation could directly affect the gut, but the trigger may also originate in the brain. Similarly, death could be due to damage in the gut or because high levels of ROS have systemic effects, or some combination of these."

The HMS researchers are now investigating the chemical pathways by which sleep-deprivation triggers the ROS buildup, and the means by which the ROS wreak cell havoc.

"We need to understand the biology of how sleep deprivation damages the body so that we can find ways to prevent this harm," says Rogulja.

Referring to the value of this study to humans, she notes,"So many of us are chronically sleep deprived. Even if we know staying up late every night is bad, we still do it. We believe we've identified a central issue that, when eliminated, allows for survival without sleep, at least in fruit flies."

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