How to Design a Solution for the N95 Respirator Shortage?

The world has a global shortage of N95 respirator. What can we do?

After diving into the problem myself, I realized that this is just a symptom of a larger problem. This problem is so much bigger than just masks. But for this blog post, we will just focus on the manufacturing and design side of the problem. I came up with the below 3 questions after going through my standard product design process:

  1. Is there a way to increase the production of melt blown fabric? If not…
  2. Is there another material that can filter well while still being breathable? If not…
  3. Is there a way to use our current supply of this material more efficiently? Yes. #FixTheMask.

Given the pressing nature of the situation, I chose to work on the one that was fastest to solve with the minimal amount of resources. But how did I get here? For any good design, you have to tear apart the current solution, figure out what is bad about each aspect of it, and make it better. Let’s break down the process of designing something that actually gets to the heart of the issue. Below was my design process.

Why are N95s respirators so good?

N95s are widely recommended as the best protection against COVID-19 because they are certified by the CDC to filter out 95% of small airborne particles.

Research suggest that viruses are typically transferred though aerosolized particles created by humans from coughing and sneezing.

It’s a fluid droplet so small that it doesn’t have enough mass to fall to the floor. Instead, it stays in the air for long period of time. So, what an N95 respirator does is in theory, it prevents you from 95% of particles that could carry a virus. (is that enough? no one knows… thats why no mask is advertised to fully protect you from COVID-19, even N95s.)

How do N95s respirators work?

N95s are filters.

A filter is a net that prevents things from falling through. But, in order for a net to actually catch things, the mesh size needs to be adequately small. Additionally, the net needs to be properly secured on the sides, so things can’t leak around the perimeter. We can simplify to say that an N95 respirator is basically comprised of two components: a net, and a seal.

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How does an N95 respirator work?

What are N95s respirators made of?

The ‘net’ portion of N95s are made of a something called melt blown fabric.

It’s a special material made from a process kind of like a cotton candy machine, but with high pressure nozzles squirting out instead of a perforated bowl spinning around in circles. The nozzles are so small and squirt at such high pressure, that the plastic comes out as these extremely thin fibers. These fibers then all stack on top of each other, and create something called a matrix. This matrix of fibers then stacks on top of each other, creating this dense forest of thin plastic strands. This is why it makes such a good net for particles.

There is a global shortage of this material (NPR). Manufacturers across the world are struggling to keep up with demand.

The machines are complicated, and the stakes of them outputting good material are very high.

So, here is our first design problem:

Is there a way to increase the production of melt blown fabric?

Melt blown fabric is so good because no other process that we know of can create such a dense obstacle course for particles to get through (i.e filters well), while still maintaining airflow (i.e breathability).

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Woven vs Knit vs Melt Blown Fabric

Cotton, silk, etc. that make up our clothes are woven or knit. Woven and knit fabrics are made by taking long thin strands of material, and effectively tying them into different knot formations. You’ll see from the photos above that all of them inherently have big holes, which means they may not make the best nets.

That would help block particles, but then air also can’t get in, making your filter not breathable, and not a good mask material.

Can’t you just stack layers of fabric on top of each other to make an obstacle course for the particle? Yes. But, for the most effective filter, let’s consider the two photos of twigs below. If you were trying to block a really small ball from rolling to the bottom of these piles of twigs, would you rather have the pile on the left, or the right? The one on the right. The same thought process applies to filters and particles.

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How to make a good filter

Fabric threads are on the order of more than 12 times larger in diameter compared to melt blown fabric threads. Melt blown fabric is simply able to make a much denser, more tightly packed stack of twigs.

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(There are also details with electrets that we will not get into here. They have to do with further increasing the ability to attract particles by charging a layer of the fabric. If you’ve made it this far and are still interested, I encourage you to check it out on your own.)

So, this is our second design problem

Is there another material that can filter well while still being breathable?

Let’s file this question away for later. For now, let’s move on.

How are N95s made?

N95 respirators take sheets of melt blown fabric and either mold them, or sew/heat press different sheets together.

So they fit well to the face.

No. In fact, there are other ways that would be a much more efficient use of resources.

There are two facets to efficiency. First, time efficiency — minimizing the time required to make the part. Second, material efficiency — minimizing the amount of materials used.

So, this is our third design problem:

Is there a way to use our current supply of this material more efficiently?

Good design is asking why until you’ve broken the problem down so far that you can’t ask why anymore. Then, look at the remaining facts and iterate to make them better. Approaching problems in this way allows you to come up with the simplest approach possible. Simple design is good design. And good design can change the world.

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The latest data and information on the Essential Mask Brace and masks in general.

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