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N95 mask


A team led by Drs. David Staack and Matt Pharr of the J. Mike Walker '66 Department of Mechanical Engineering, along with Dr. Suresh Pillai from the College of Agriculture and Life Sciences, is utilizing the electron beam facility at Texas A&M University to sterilize and decontaminate personal protective equipment, including gowns, face shields, and most importantly, N95 respirator masks. In this episode, Dr. Staack discusses how the team tested their methods, what implementation could look like in the real world, and the potential impact these lessons learned could have beyond the renewal of PPE.

This information was part of a larger conversation found in the SoundBytes episode. A full transcript of the episode is located below.


Hannah Conrad: Medical grade masks are a vital piece of equipment in the fight against COVID-19. However, by design, they're only made to be worn once, leading to a shortage in supply. But what if there was a way to recycle these masks so they could be returned to healthcare workers sterilized and help reduce the potentially dangerous lack of them? Fortunately, Aggie researchers are on the verge of a solution. This is SoundBytes. Welcome to Engineer This.

Steve Kuhlmann: A team led by Drs. David Staack and Matt Pharr of the J. Mike Walker '66 Department of Mechanical Engineering, along with Dr. Suresh Pillai from the College of Agriculture and Life Sciences, is utilizing the electron beam facility at Texas A&M University to sterilize and decontaminate personal protective equipment, including gowns, face shields, and most importantly, N95 respirator masks. I'm Steve Kuhlmann, and my co-host Hannah Conrad, who you heard earlier, and I are joined by Dr. Staack to discuss how the team tested their methods, what implementation could look like in the real world, and the potential impact these lessons learned could have beyond the renewal of PPE.

Dr. David Staack: Well, it seemed kind of obvious for us that it was worth trying, because we had kind of the tools in place already to try these things, right. You know, we scrounged around in our cupboards and found what masks we could and respirators we could, right. Sent those through the ebeam facility, probably within several weeks, right. We had put them through, and then we proceeded to do what we could do in-house in terms of testing. Some mechanical tests on the materials, so the mask materials themselves, right, we looked at them with an SEM, right, a high fidelity microscope so we can see even nanostructures in these materials, right? Is there any kind of discoloration? Is the fabric as strong as it used to be, so actually pulling and testing the fabric in a tensile test machine. They passed, right. And so that was very favorable and we thought things were going to work out well. We looked at the literature, right. Electron beam is a well-known sterilization method. So, there's kind of a dose that will kill just about anything in terms of contaminants — did various doses, did these mechanical tests that we had access to. And then after that, we looked to do kind of the more formal particulate filtration testing. And that's when things got complicated. We had to go to a external lab to do testing. In this case, it's an NIOSH test. The little stamps that all the masks have on them is NIOSH-tested. And what NIOSH does is they do a particulate test of a 300 nanometer particle and see what fraction of that 300 nanometer particle is stopped. Our results showed that the materials, with even a tiny bit of electron beam dose, even less than the sterilization dose, were dropping from an N95, which means it's blocking 95% of 300 nanometer particles to something closer to an N65 or an N75. It had drop to 6, and then at higher doses, it was all just flat at 65. So it's kind of it lost this ability, but it only lost it so much and it didn't lose it any more than that. The details get into really how these filters work. P robably when we think of a filter, right, you think there are small holes, right? And if you make the holes small enough, it will stop the particles, right? And so that's why people sew together their own masks and they pick materials from which to sew them, right? Oh, you want something where you can't see through it with your eye. You want a tight, high thread count, maybe. You know what are all these little tricks that maybe make a homemade mask better. And we're thinking about mechanical filtration. And that's really just half of how a very high quality filter works. If you try to stop really, really small particles and the holes are really, really small, you're not going to be able to breathe through it. So there's another technique which people use to trap particles when they're very small, and that is effectively static charge or electric charge. So right, you guys know, you, you know, rub a balloon on your head, and you get some static charge between the two dissimilar materials. And if you were actually to take that balloon, and you know, you had the sunlight shining in and you could see the dust particles, you would see those dust particles actually be attracted to the balloon, and they would stick to it. So that process is the electric side of how you can capture very, very small particles. So actually, the materials inside of a mask are made such that they hold static electricity. So there's three layers in a typical mask. It's polyester, polypropylene, polyester. And the polypropylene material in particular is very good at holding negative charge. When they're manufactured, they actually put a negative charge on this material, and that negative charge can stay on the material for as long as the shelf life is of the product until you go around and you use it. What was happening with the treatments that we were doing in the electron beam facility is this electric charge effect, which works on really, really tiny particles, was getting disrupted. All of our mechanical testing, right, SEM, everything looks the same. The material almost as strong as it used to be. Right all those mechanical effects were working just fine. Mechanical effects tend to be good for really large particles down to about a micron, and then kind of below a micron down to the nanometer range mechanical effects stop working as well. The electric effects work really well on the tiny, tiny particles and stop working as you get to larger particles. One of the reasons they do the testing at 300 nanometers is it's where the electric effect and the mechanical effect are worst. So it's kind of the hardest particle to capture. When we're talking about these aerosolized viruses, they're probably in the 100 to 200 nanometer range. So it's actually the electric effect, which is working on them. And so that's an important aspect to think about if you're trying to make a respirator that's filtering for viruses, right? If you're filtering for droplets, like a lot of what our cloth masks are designed to do, then you're just mechanically stopping some, you know, water droplets, which might have virus in them. So we actually set up some systems recently to go in and measure the electric field on the surface of the mask. The first time we did it, it was actually just a static field and we had like a little piece of tissue paper and we looked and we saw if the mask could lift the tissue paper up off the table, and they can out of the box, you know. You get within a few millimeters and you can see this tiny fiber will jump up onto the mask. And we found out that what we were doing in the electron beam facility during the sterilization process was disrupting the existing charge but not disrupting the ability to hold charge. So since then, we've been able to use techniques very similar to what they use in the original manufacturing of the masks to put charge back on the mask. We don't know yet if it's going to hold for four years like it does when they are originally manufactured by 3M.

Steve Kuhlmann: Still better than nothing. That's great.

Dr. David Staack: Yeah, it's kind of an added step is the way we would envision it is that you would go through a sterilization step, and then after you went through the sterilization step, you would go through a repoling step where you put charge back on the mask. And so what we have kind of planned in the next month is to do that: to irradiate, repole, sent to NIOSH and see if those masks recovered their full functionality. A little more complicated, maybe than we thought when we first got into it, and it kind of made us think too about you know, if you're DIYing a mask, could you DIY a mask that has electric properties? Could you make your mask out of silk and polypropylene, right? Because silk holds positive charge, polypropylene holds negative charge. And so you can actually rub those two materials together and get them to make static charge.

Steve Kuhlmann: Yeah. You mentioned the idea of maybe trying to find a way that people could add that charge at home. And me, I'm just thinking about the idea of people at home trying to add this and—

Hannah Conrad: My hair is like standing on end just from that. I have curly hair, and it's just like slowly going up.

Dr. David Staack: This static charge, it's nothing worse than, right, pulling a sweater over your head, right?

Steve Kuhlmann: More than the, more than the shock itself. I was kind of thinking about like with kids and even adults that if they were able to do something like that, you know, you mentioned it was cool seeing how the masks actually worked. That's like a science lesson for everybody.

Hannah Conrad: What is most exciting to you about this research?

Dr. David Staack: Obviously we would love to have an impact on healthcare workers. We're also finding like right now there are, there are applications for what we're doing which aren't just healthcare workers. There's other people who, in order to get back to work, need to have ways to sterilize the tools they use. For example, we had someone approached us from a media company where they have a film crew, and they want to sterilize their stuff after they use it for the day before the next crew uses it. You know, so we literally, we threw a camera and a bunch of electronics in our trailer and applied the dosing and actually we applied a ton of dose because we're like, you know, how much can these take, right? They can take a lot more than these disposable masks, right? These disposable masks are designed to be thrown out. Right, but you know, we threw a camera and we threw electronics in there, and they were all fine, and they didn't even notice. You know, there was no material degradation or functional degradation at all. I could use a device, pass it through this machine; it would come out. Someone else could use it. Right, it would be equivalent to a brand new device in terms of sterility.

Steve Kuhlmann: So, we've talked a lot about the sterilization side of this. What might an application of this look like whenever you say, partner with a hospital and have them run their PPE through?

Dr. David Staack: Sure. One is the electron beam facility, right, which is a very good sterilization facility, but it's a fixed infrastructure. And the other we've been working with is the plasma decontamination system. And so we've actually put together a facility; it's about, it's like a cargo container, right, a 20-foot cargo container that we can fill with PPE. Right now it only has three, four shelves in it but conceptually you can fill it with PPE. It's not quite as effective as the electron beam at sterilization; it takes a little longer, right. The electron beam, I mean, you sterilize these things in 90 seconds, right? Pew pew pew. This takes four hours, but you can do it in batch. So for the fixed infrastructure, what we envision is, typically there's a medical waste kind of pipeline coming out of a hospital. What they would do is they would look at their medical waste, and they would say, you know, this stuff is really bad and just has to go in the garbage. And then this stuff is lightly used, and it's probably contaminated, but it could be reused. And what they would do is they would take that stream and they would package it up, right, and kind of you double bag it right and then kind of the bacteria and viruses and all the contaminants are contained in the bags. You put it in a cardboard box. With an electron beam, right, the cardboard box, just the way a beam works is it penetrates through the material. You put in the back of a truck, you drive it to the ebeam facility. If we were solely going for sterilization, you would pass that box through the facility. It would come out of the facility sterile. It would probably be repackaged to that point, right? Because you'd want to track, you know, this has been through the ebeam sterilization facility. You know, XYZ, it got this dose, it's good. It's kind of a repackaging of sorts for the clean material. So boxes like that, right? If you really wanted to, we estimate we could do 5,000 to 10,000 respirators an hour at our little facility here at A&M. The other approach is the plasma facility that we're working on, which is a trailer right, and we've set that up somewhat. We're doing testing right now for system, for devices that will go off to get tested at NIOSH. But this is you drive up with the truck. We parked the truck on the loading dock in the hospital. It's got a bunch of shells in it. They would load their PPE up onto the shelves. Close the door, turn the cycle on for four hours; we'd run through a cycle decontaminating the surfaces. After four hours, you turn it off, and you step in and you would grab your PPE back. Again, you go through a tracking process, right, some sort of labeling and some sort of tracking for how many times it's been recycled and who used it and things like this. And we envision that type of thing being able to do about 2,000 masks per cycle, and probably another 150, 200 gowns per cycle.

Jenn Reiley: Hey, it's your producer Jenn Reiley here with an update on this story. Dr. Staack reached out to us and let us know that on August 28, his team heard back from a CDC testing facility that had received some of the sterilized respirators. The 12 respirators Dr. Staack's team decontaminated in their plasma treatment trailer passed the NIOSH N95 test. Basically, their system is working! We were all excited to hear this news, and we wish the team continued success. Now, back to the episode.

Hannah Conrad: What's it like to be working on a project that can help so many people?

Dr. David Staack: There's good and there's bad, right? So the good part is that you feel like you can do good. And then, and the students are motivated, and everybody's motivated to come in and do work. And then one of the bad parts is when you hit a little stumbling block, and you're like, "Ah, you know, they didn't pass the N95. Right, why not? They should have. I wish they did. What's going on here?" Right, it looked like everything was been worked out. And then there are other stumbling blocks, like, "You know, I think this is working. We just need a little, you know, a little more input, a little more connection with the right people. We need to talk to somebody about how to get this implemented." Right, so for the trailer that we're working on now, we didn't have gowns. We had one gown that we used for three months. The ones that we're using for testing are ones that aren't going into people's hands to use, right. And so there's a little bit of you know, is what I'm doing important enough to be taking 50 respirators out of circulation in order to do testing on them, right? And so we did a lot of testing with just raw materials, like we just bought polyester and we bought polypropylene, which are the components you would use to make a mask, to see what are we doing to these materials before we went in and we threw actual masks and respirators in. And like, with my students, I'm like, you know, we have this mask, we're going to do a real study here. We're going to ship this out to the CDC to get tested. Treat it like gold. So be very careful with your procedures; don't mess up anything, right? So those are all kind of in the back of your head as you're working, right? You're trying to help, but you're trying to not, you know, get in the way of things either. And you say in the back of your mind, you know, it might not work out, our pace might not be fast enough. We might not figure it all out right now. But we're going to write all this up, and we're going to publish it because one thing we noticed is there wasn't any literature on recycling PPE.

Steve Kuhlmann: Given what sounds like the I mean relatively quick turnaround that you can get on some of these, it really sounds like if it could be implemented, it could really make a pretty big impact on what I think is fair to say is the dramatic need for PPE right now.

Dr. David Staack: Yes, I would say that the need for PPE is not as dire right now as it was, right. And that's because some manufacturing lines have come up. But there's still stories of people wearing ponchos, and they shouldn't be, right. They should be protected with the best, the best, the best material that we can get to them.

Hannah Conrad: Tune in next episode when our student hosts chat with the SEC corporate relations co-chair James Kirkland about networking tips and international internships on a new episode of Just a SEC. Until then, stay safe and Gig 'em.

Steve Kuhlmann: Thanks for listening to the Texas A&M Engineering SoundBytes podcast. The views and opinions expressed in this podcast are those of the hosts and guests and do not necessarily reflect the official policy or position of the Texas A&M University System. Soundbytes is a part of the Texas A&M Podcast Network. To find more official Texas A&M podcasts, go to Thanks and Gig 'em.