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.

woman making homemade face masks
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.

This is what aliens would 'hear' if they flew by Earth

A Mercury-bound spacecraft's noisy flyby of our home planet.

Image source: sdecoret on Shutterstock/ESA/Big Think
Surprising Science
  • There is no sound in space, but if there was, this is what it might sound like passing by Earth.
  • A spacecraft bound for Mercury recorded data while swinging around our planet, and that data was converted into sound.
  • Yes, in space no one can hear you scream, but this is still some chill stuff.

First off, let's be clear what we mean by "hear" here. (Here, here!)

Sound, as we know it, requires air. What our ears capture is actually oscillating waves of fluctuating air pressure. Cilia, fibers in our ears, respond to these fluctuations by firing off corresponding clusters of tones at different pitches to our brains. This is what we perceive as sound.

All of which is to say, sound requires air, and space is notoriously void of that. So, in terms of human-perceivable sound, it's silent out there. Nonetheless, there can be cyclical events in space — such as oscillating values in streams of captured data — that can be mapped to pitches, and thus made audible.

BepiColombo

Image source: European Space Agency

The European Space Agency's BepiColombo spacecraft took off from Kourou, French Guyana on October 20, 2019, on its way to Mercury. To reduce its speed for the proper trajectory to Mercury, BepiColombo executed a "gravity-assist flyby," slinging itself around the Earth before leaving home. Over the course of its 34-minute flyby, its two data recorders captured five data sets that Italy's National Institute for Astrophysics (INAF) enhanced and converted into sound waves.

Into and out of Earth's shadow

In April, BepiColombo began its closest approach to Earth, ranging from 256,393 kilometers (159,315 miles) to 129,488 kilometers (80,460 miles) away. The audio above starts as BepiColombo begins to sneak into the Earth's shadow facing away from the sun.

The data was captured by BepiColombo's Italian Spring Accelerometer (ISA) instrument. Says Carmelo Magnafico of the ISA team, "When the spacecraft enters the shadow and the force of the Sun disappears, we can hear a slight vibration. The solar panels, previously flexed by the Sun, then find a new balance. Upon exiting the shadow, we can hear the effect again."

In addition to making for some cool sounds, the phenomenon allowed the ISA team to confirm just how sensitive their instrument is. "This is an extraordinary situation," says Carmelo. "Since we started the cruise, we have only been in direct sunshine, so we did not have the possibility to check effectively whether our instrument is measuring the variations of the force of the sunlight."

When the craft arrives at Mercury, the ISA will be tasked with studying the planets gravity.

Magentosphere melody

The second clip is derived from data captured by BepiColombo's MPO-MAG magnetometer, AKA MERMAG, as the craft traveled through Earth's magnetosphere, the area surrounding the planet that's determined by the its magnetic field.

BepiColombo eventually entered the hellish mangentosheath, the region battered by cosmic plasma from the sun before the craft passed into the relatively peaceful magentopause that marks the transition between the magnetosphere and Earth's own magnetic field.

MERMAG will map Mercury's magnetosphere, as well as the magnetic state of the planet's interior. As a secondary objective, it will assess the interaction of the solar wind, Mercury's magnetic field, and the planet, analyzing the dynamics of the magnetosphere and its interaction with Mercury.

Recording session over, BepiColombo is now slipping through space silently with its arrival at Mercury planned for 2025.

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Photo by Reinhart Julian on Unsplash
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