N95 masks could soon be rechargeable instead of disposable – TechCrunch
The pandemic has resulted in N95 masks quickly becoming one of the most sought-after resources in the world as billions of them were burned by key workers. New research could lead to an N95 that you can charge instead of throwing it away – or even one that continually refills for maximum effectiveness.
The system proposed by researchers from Technion-IIT in Israel and the Tata Institute for Basic Research in India is not a decontamination system as expected. Instead, it focuses on another aspect of N95 masks that makes them less effective over time.
N95 use both mechanical filtration, which traps particles in a matrix of microscopic fibers, and electrostatic filtration, which attracts particles to surfaces that carry a static charge. It’s like the old trick where you rub a balloon on your head and it sticks – but in the micrometer range.
The combination of these two methods makes N95 masks very effective, but the electrostatic charge, like any charge, dissipates after a while when air and moisture flow over it. While decontamination from UV radiation or high temperatures can help prevent the mechanical filter from becoming a tiny petri dish, it cannot restore the electrostatic charge that acted as a second barrier to entry.
In a newspaper published in the journal Physics of Fluids, Dov Levine and Shankar Ghosh (from Technion and Tata respectively) show that it is possible to charge the filter of an N95 to a point where it was close to standard efficiency. All you have to do is place the filter between two plate electrodes and apply a strong electric field.
“We found that the total charge deposited on the masks strongly depends on the charging time … although the original value is almost reached again after a 60-minute charge at 1000 V,” the researchers write in their paper.
However, health care workers are unlikely to disassemble their masks after each shift. While a service and a specific type of mask could be set up (and if it were to be effective), the team also looked into the possibility of a mask with a built-in battery that constantly charges itself:
A solution that can help replenish the lost charge on the masks in real time would be desirable. In this section we introduce a proof-of-concept method of charging the masks, which is a logical extension of our charging method.
We have tested a technique with which the filter material maintains its load and therefore its filtration efficiency. Since the required currents are extremely small, a large battery is not required, and a small, compact and practical solution is possible.
The picture above shows a prototype that the team believes works reasonably well.
Of course, it’s not ready for use just yet. IEEE Spectrum asked Peter Tsai, the creator of the N95 mask, for his opinion. He suggested that the team’s method of testing filtration efficiency was “probably questionable” but did not question the rest of the study.
Although it won’t be in hospitals tomorrow or next week, the team notes that “our method can crucially be carried out with readily available equipment and materials, and therefore can be used in both urban and rural settings.” Once tested thoroughly these rechargeable masks can appear anywhere. Let’s hope so.