Stopgap Surgical Face Mask (SFM)

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Fri, 2020-04-03 18:59

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QR Code for https://3dprint.nih.gov/discover/3dpx-013429

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I see the material selected was Nylon. Any feedback on printing this in PLA?

We selected nylon powder bed manufacturing as our initial release due to available information on biocompatibility and disinfection.  That information is more difficult to find for other 3D printing materials / methods.  At this time, we cannot recommend PLA for this application.  However, we would like to release additional guidance on other 3D printing materials and methods.  If anyone can provide such info, please reach out to me to expedite this process.

There are some optimizations that could be made to the design to print on FDM more easily, and without supports. A great example are the models coming from La Factoria. Basically, if you design it to print from the nose up on an FDM bed you'll get better results. The way that you have it designed now, it could print on the nose but would need supports. Can you print with supports? Sure. but less to clean up means better fitting snap-together parts.

Note:  I'm a software engineer by trade so take this with a grain of salt.  Just doing some research on this as well.

I found this paper on PLA and PETG prints that can be sterlized using low temperature hydrogen peroxide gas plasma sterlization.

https://benthamopen.com/FULLTEXT/TODENTJ-13-410#r8

There are some variants of PETG that say in their marketing that they are food safe and biocompatible.  I've been printing the NIH face shields in PETG because it's easier to disinfect than PLA.

Any word on using FDM with nylon filament?

Chris,

 

I am working on a design that can be printed on a an FDM printer with the obvious caveats. The materials that you are utilizing for this have to be fairly expensive? It looks like you are using laser sintering of nylon and objet type printers. I believe this could be printed succesfully using PET-G. I have printers that have been custom designed to do orthopedic printing (casts braces etc..). I can print this in a PET-G that ISO 10993 USP Class VI and see how it comes out. There are some features that could be designed better that would allow this design to be printed on an FDM easier. If you would like me to print and evaluate this on my printers please let me know. I can send you the prints. On another note, I am working with the VA Center in Indianapolis on similar type projects.

Thanks,

 

Dave Pemberton

MedFab3D

317-695-5841

On this website , one can find a PLA with copper nanoparticles which kills viruses and bacteria and thereby makes these masks reusable :

https://copper3d.com/hackthepandemic

Hi Chris -

I'm aware of 2 biocompatibile and autoclaveable 3D printed material, made by Form Labs: the Surgical Guide resin and the Dental resin: https://dental.formlabs.com/materials/#surgical-guide

They've tested it to ISO 10993 for surface contacting med devices, which have limited contact with the body, e.g. on the skin. 

Have you advanced this beyond the clinic and been approved for emergency use by the FDA? I don't have the ability to offer many resources, but I can help with making parts and connecting to the demand regionally (San Diego).

https://www.fda.gov/emergency-preparedness-and-response/mcm-legal-regulatory-and-policy-framework/emergency-use-authorization#2019-ncov

Info from Formlabs on biocompatibility: https://forum.formlabs.com/t/biocompatibility/24118

 

Good afternoon Chris, I hope you and your family are safe. Thank you for ;a; the provided material. Would you happen to have the validation test results of your printed mask from UW? 

Thank you. 

 

Chris,

We would love to start producing this mask with FDM biocompatible materials and we can provide the material/product for testing.  Are you able to provide a .stp file for the mask?  We may need to make some revisions to avoid support material.  Give me a call or email and we can discuss next steps.  484-929-3590 and matt.white@americanadditive.com

Hi Chris,

maybe worth taking a look at the information Prusa just released about disinfecting their face shields. From what I could gather, they partnered up with different institutions which performed different methods to sanitize their protectors. There is a table with methods and their efficacy https://www.prusa3d.com/covid19/
 

PLA can be sterilized using 70% or higher IPA. The surface tension of IPA is very low, about 23 dynes/cm MEANING that it takes very little energy to break the surface tension allowing the IPA to get into pores smaller than viruses.. How do i knw this, because a friend of mine makes filters that filter viruses out of blood andthey are REQUIRED by LAW to ONLY use IPA 70% or higher.  IPA has no issues when sanitizing PLA. I am a Mechancial and materials engineer. This is why you have to soak parts in bleach water for 1 to 2 minutes because the surface tension is 73 dynes/cm.

Even baricide, aka Benzalkonium chloride will work. it has low surface tension, BUT IPA IS BEST!!

 

PLA can be sterilized using 70% or higher IPA. The surface tension of IPA is very low, about 23 dynes/cm MEANING that it takes very little energy to break the surface tension allowing the IPA to get into pores smaller than viruses.. How do i knw this, because a friend of mine makes filters that filter viruses out of blood andthey are REQUIRED by LAW to ONLY use IPA 70% or higher.  IPA has no issues when sanitizing PLA. I am a Mechancial and materials engineer. This is why you have to soak parts in bleach water for 1 to 2 minutes because the surface tension is 73 dynes/cm.

Even baricide, aka Benzalkonium chloride will work. it has low surface tension, BUT IPA IS BEST!!

 

We are reusing N95 filtering facepiece respirators by storing them for extended (4 days) in paper bags.  I'm assuming if all we have is PLA/ABS we can use the same technique with these.  Thoughts?  The universities, tech clubs, etc, have PLA/ABS available now.

https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguidanceextuse.html

Have you tried SLA surgical materials? 

I understand that FDM printing, and for example PLA plastic, has serious fundamental problems which make it not a disereable process to manufacture PPE respirator face masks. I believe this is due to the porus nature of FDM prints, and how they can have holes in the surface dispite looking like a solid object.

Based on this understanding, I would like to ask is SLA printing any better? Also, would skipping 3d printing entirely and just fabricating these from molds and make solid urethane rubber castsings both safer and economical? There are resins for casting that are certified to be human safe and that have long term high tempature/heat resistance such as use in an autoclave.

My intention is to follow that path towards an improved face mask that is both safe (by meeting safety standards) and easier to mass produce. 

Thank you.

I just bought the Elegoo Mars 3D resin printer. Can I make PPE masks for teachers using this? I teach middle school and I'm 60 years old. I really need a dependable mask with replaceable filter, not just for me but for many of the teachers my age that I work with. The resin I use is a water washable type with UV curing. Will this be safe to use? And, because we have to teach children, I'm trying to figure out how to add a microphone so we can be heard. If you know anyone that can help, that would be great. Thanks

Sorry, I simply cannot find the manufacturing instructions - please point me in the right direction.  Also, while waiting does it have to be Nylon?

Hi Fran,
There are 2 PDFs linked from the "Extras" tab with printing details. It appears this model is designed for SLS or MJF types of printing, not FDM, which is the type of 3d printing that uses rolls of filament. So I'm not sure that it's suitable for FDM.

Click on the "Extras" tab - there are 3 files.

Click on the "Extras" tab - there are 3 files.

I saw the .stl files, but no instructions for 3D Printing - is this not ready for 3D Printer printing?

Fran,

Instructions can be found in teh "Extras" tab along the left side of the image..

However, this does not appear tp be for FDM printing.

 

Hi Fran, 

You can use a program called Ultimaker Cura to take the .stl files and slice them into gcode.  Then just load the gcode files onto your printer and you're good to go!

Fran, I added this comment to the "General information" section: "See the Extras tab for detailed information including the Instructions For Use and Manufacturing Instructions."

Do you have some printer that you can recommend?

Please note that the common hospital practice of sterilization using vaporized hydrogen peroxide (VH2O2) may not be compatible with nylon. See, for example, page 13 of this document: https://ww1.steris.com/onbDocs/V440/0/1375474.pdf

That is definitely a valid concern, but I haven't noticed any adverse affects when using liquid H2O2 on Nylon. Although it might be differen because it wasn't vaporized. I also can't seem to find the reference on page 13 where is states incompatabilitiy with nylon. However I did see the table on page 19 which highlights that there might be some cosmetic fading even though the functionality won't change much.

Do you happen to have any other references that demonstrate the incompatability of VH2O2, or and forms of hydrogen peroxide for that matter, with Nylon materials? I am interested in learning more about this. 

Sorry, that was the wrong link. See page 13 here: https://ww1.steris.com/onbDocs/V405/1251/664610.pdf It lists four different nylon items that were tested. One failed after the 39th sterilization cycle, two showed fading and one was unaffected. In this report: https://allied-group.com.au/wp-content/uploads/2018/05/STERIS-VHP-LTS-V-Technical-Monograph-2016-2.pdf page 5 lists nylon as having "lower" compatibility with H2O2 gas. And here: https://ww1.steris.com/onbDocs/V446/0/1721934.pdf in the footnote to table 21, page 17 it says " Some grades of Nylon, Delrin, and Radel devices may have limited life after repeated sterilization."

I'm not in a position to evaluate the extent to which these concerns apply to the material in this mask and its intended use case. But it may be worth some investigation.

This is helpful, thank you. It looks like some more physical testing might be in order. 

Hi Chris, Is there a small and large size of this mask available as well or just the medium size?

Colinrdodson, I just added a small size.  We hope to add more sizes as we can do more fit testing. Please check this page frequently for updates.

Do you have a suggested filter media?  surgical drapes?  

James, we are currently recommending the use of Surgical face masks meeting ASTM F2100−19. One surgical face mask will make approximately four filter patches.  Please see Appendix B in the attached Instructions for Use in the Extras tab.  We are working hard to find alternate filter materials that do not consume existing medical resources.  We don't recommend surgical drapes.  Please check this page for updates.

Hi, I asked a filter house about providing sheets of filter material ,Why cut up masks!  Here is a MERV13, which might be a little porous, but its an example of asking a vendor to make resources available. Ask em all!  https://www.airfiltersdelivered.com/20x36-merv13media-p=P25media

Good evening Chris et al, 

I was wandering through the local big orange home improvement company the other day looking for filter media alternatives as our local stores have been out of masks since early February.  There are two on-shelf alternatives that I saw at that time, and that trip motivated me to research other available alternative filter options.  

Option 1 - shop vacuum filters, including both pleated canisters and vacuum bags, as well as reusable over-filter cover material.  I have provided a link for the three different options directly below.  Please take a minute to look over the HOPA/ OSHA pleated filter in particular, as it has some interesting specs similar to N95 respirator material.  

This first option is built with "HEPA material", and is rated at an equivalent of 0.3 microns+ filtering.  As I'm sure you're aware, N95 masks are rated at filtering at least 95% of particles greater than 0.3 microns.  Technically, according to the information listed on the website "Enviro safety products" below (and many others I've read), HEPA-certified filters remove +99.97% of material over 0.3 microns, thereby making them "better" than N95m  masks at filtering.

HEPA (material) pleated filter. filter bags:

https://images.homedepot-static.com/catalog/pdfImages/67/67e6cc1f-cba4-4fe6-bfe2-18d8c100630b.pdf

Fabric over-filter material (I could not locate filter media density or equivalency on this product, but can inquire with the Mfg. on the same):

https://www.homedepot.com/p/Multi-Fit-Disposable-Dry-Filter-with-Retainer-Band-for-Select-Genie-and-Shop-Vac-Wet-Dry-Vacuums-3-Pack-VF2002/202077243

HEPA/ N95 reference link:

https://www.envirosafetyproducts.com/resources/dust-masks-whats-the-difference.html

 

Option 2 - HVAC filters.  Through my research, the big box stores shelf-stock many different filters that France up to ~MERV 14 =/- (Minimum Efficiency Reporting Value).  HVAC filters rated at MERV17-MERV20 also filter contaminants above 0.3 microns, the same as a HEPA rating.  I have found some different HCAV filters that also purport to be HEPA certified (actual conformity TBD).  

MERV-rating reference links:

https://www.serviceexperts.com/indoor-air-quality/remember-to-look-for-the-merv-rating-for-your-air-filter

https://www.grainger.com/know-how/equipment-information/kh-what-is-merv-rating-air-filter-rating-chart'

 

I am happy to assist however I can, whether it's research, Mfg. contact, design assistance, etc.  I look forward to helping out. 

Stay safe, 

Brandon L. 

Good evening Chris et al, 

I was wandering through the local big orange home improvement company the other day looking for filter media alternatives as our local stores have been out of masks since early February.  There are two on-shelf alternatives that I saw at that time, and that trip motivated me to research other available alternative filter options.  

Option 1 - shop vacuum filters, including both pleated canisters and vacuum bags, as well as reusable over-filter cover material.  I have provided a link for the three different options directly below.  Please take a minute to look over the HOPA/ OSHA pleated filter in particular, as it has some interesting specs similar to N95 respirator material.  

This first option is built with "HEPA material", and is rated at an equivalent of 0.3 microns+ filtering.  As I'm sure you're aware, N95 masks are rated at filtering at least 95% of particles greater than 0.3 microns.  Technically, according to the information listed on the website "Enviro safety products" below (and many others I've read), HEPA-certified filters remove +99.97% of material over 0.3 microns, thereby making them "better" than N95m  masks at filtering.

HEPA (material) pleated filter. filter bags:

https://images.homedepot-static.com/catalog/pdfImages/67/67e6cc1f-cba4-4fe6-bfe2-18d8c100630b.pdf

Fabric over-filter material (I could not locate filter media density or equivalency on this product, but can inquire with the Mfg. on the same):

https://www.homedepot.com/p/Multi-Fit-Disposable-Dry-Filter-with-Retainer-Band-for-Select-Genie-and-Shop-Vac-Wet-Dry-Vacuums-3-Pack-VF2002/202077243

HEPA/ N95 reference link:

https://www.envirosafetyproducts.com/resources/dust-masks-whats-the-difference.html

 

Option 2 - HVAC filters.  Through my research, the big box stores shelf-stock many different filters that France up to ~MERV 14 =/- (Minimum Efficiency Reporting Value).  HVAC filters rated at MERV17-MERV20 also filter contaminants above 0.3 microns, the same as a HEPA rating.  I have found some different HCAV filters that also purport to be HEPA certified (actual conformity TBD).  

MERV-rating reference links:

https://www.serviceexperts.com/indoor-air-quality/remember-to-look-for-the-merv-rating-for-your-air-filter

https://www.grainger.com/know-how/equipment-information/kh-what-is-merv-rating-air-filter-rating-chart'

Option 3 - prepackaged CPAP filters.  I also came across a few different types of CPAP filters.  These are not necessarily certified as HEPA-equivalent BUT are typically medically approved (from at least some valid Mfg.) that I have found.  I saw many different companies that individually package these filters, which would be a big plus.  Additionally, the filters are generally cut into fairly common shapes/ sizes.  These filters, as I have learned, work to filter the intake air side of the CPAP machines, thereby directly filtering the air that the end-user is breathing.  

I am happy to assist however I can, whether it's research, Mfg. contact, design assistance, etc.  I look forward to helping out. 

Stay safe, 

Brandon L. 

My company can produce approximately 100,000 filters for this type of mask - approximate size 2.5x2.5 inches.  They have been tested to meet the N95 standard.  Please let me know if you are interested.  ross.kayuha@nanofibersolutions.com

 

Any qualitative or quantitative fit test accomplished on the mask? 

Lt Col Jay Vizcarra, yes, we have conducted qualitative fit testing with over 50 clinicians.  We are reviewing that data to see which sizes and shapes we should add.  That testing led us to add a small size in addition to the medium.  We feel the qualitative fit testing is sufficient to meet the requirements of a surgical face mask.

I have performed quantitative testing with this design (Portacount Pro+) and many others. This Stopgap Masks out performed a surgical mask and cloth face coverings, but all were WELL below the standard for an N95 respirator. We have had increased fit factor numbers in limited tests with various seal materials added to periphery. Dental lab putty has been most effective. HEPA filter performed slightly better than blue intrument wrap (3-ply polyprolene) but we have more of teh polyprolene and it seems more resistant to tearing. 

1. Is gasket material recommended for fit against face? If so please include in build instructions and BOM

2. Filter material also needed. Please advise.

James, for filter media, please see the Extras tab, Instructions for Use, Appendix B.  We are not recommending additional gasket material for sealing against the face to keep the design as simple as possible.  This is similar to existing surgical face masks that do not achieve a perfect seal against the face.

This would be more reliably printed if the face was flat. Consider putting the insert in the back of the mask.

James, I don't understand your suggestion.  Can you contact me directly by logging in, click my name, then contact?

This is about FDM printers, I noted in a previous comment. Having the main part of the mask's "nose" totally flat makes it easier to print without support (or at all) on an FDM printer).

Chris,

I believe what James is referring to is the fact that many consumer 3D printers use a flat build surface and then lay down layers of material on top of each other to build parts.

In order for these printers to be effective they need to print from a flat surface. 

I would like to be able to print this in PLA on a printer that uses the above method.

Here is some info on biocompatibility of PLA: https://www.sciencedirect.com/science/article/abs/pii/S0169409X16300989

I have a question regarding the design: Is it important for the mask to be printed from a flexible material? I know that it is vital to get a good seal between the face and the mask. I have never worked with powdered nylon prints and do not know how rigid they are.

I agree with this design revision idea, It would make it much easier for FDM printers to print if the front face was flat. If you were to cut out the section that you snap the cover onto, and flip it 180, so that the flat part (currently facing in towards the face) would face out. Then the filter insert would be on the inside of the mask and you would have a flush bottom to print from. You might have to tweak the filter insert and cap to not be rubbing up against the mouth. Possibly making it thinner etc. 

Chris first thanks for sharing this. What the others said about the FDM printability is correct. HOWEVER if I could get the STEP file I think it would only take a simple modification to the front of the mask to make it printable via FDM. I do not think it needs to be completely flat so I could make the design work with the front mount filter retainer.

I am very interested in producing these on my FDM printer and would be happy to make the change. I just cannot do it with STL or  X3D files.

I've done a remix of the mask to make it FDM printer friendly but I don't know how to get it up on this site. When I try to publish it as a remix, it won't let me upload the .STL file. Tells me it's an unvalid file type.

I moved the cover retaining ring from the front of the mask to the inside so that the mask has a flat surface to sit on the build plate. The filter cover fits inside the mask instead of outside. Not sure if it'll clear a wearers nose though since I haven't printed it out yet. I also changed the shape of the elastic cord tabs so that they will print without supports.

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