TL;DR: I believe #BlackLivesMatter. I still can’t say anything more
eloquently than what has been said by others elsewhere, so I’m going to chip
into the cause in my own way. If you’ve donated to a reputable social justice charity,
I’m more than happy to send you some 3D Printed #earsavers or touch-free door
openers.
Despite law enforcement agencies across the country telegraphing they don’t believe
so, black lives do matter. To help the cause in a small way, I designed a new
earsaver and a touch-free door opener/keypad stylus.
The earsaver is a modified version of the NIH-approved design found here: https://3dprint.nih.gov/discover/3dpx-013615. No critical outside dimensions were altered, and the part remains very flexible. Earsavers are very useful for anybody who needs to wear a mask (aka EVERYBODY WHO LEAVES THEIR HOME). You put this on the back of your head and hook your mask straps around it instead of around your ears. This takes the pressure off your ears and makes wearing the mask much more tolerable.
Creating the door opener/stylus was a bit more involved; I created the design from scratch, using a few existing designs as inspiration. The hook is useful for opening door handles without touching the surfaces. A strip of copper tape wrapped around the fist allows the stylus to function on capacitive touch screens, as long as you touch the bottom of the strip with your thumb. This is useful for pressing buttons at the self-checkout line in grocery stores.
If you’d like some of these doodads, I’m happy to send them to you free of
charge. Since I literally finalized the design at lunch today, I don’t have a huge
stockpile right now. For now, I’m going to prioritize those who have donated to
reputable social justice related charities, but I aim to eventually provide
these for anybody who wants them, so feel free to reach out!
TL;DR: I made a working respirator using a small stockpile of N95
replacement filters I have… However, since a local hospital has the appropriate
adapters and real respirators, for the greater good, it makes the most sense
for me to simply donate my materials.
Two weeks ago, I completed the design of, and successfully tested a
prototype N95 respirator. Before everything was sold out, I managed to buy a
small stockpile of about forty 3M 5N11 particulate filters, typically used for
industrial purposes. Unfortunately, I didn’t find any of the requisite adapters
nor compatible respirators.
Luckily, what I did find was this great project called S.A.F.E
(self-assembly filtration unit for emergencies) from the Medical University of
South Carolina (MUSC) (https://web.musc.edu/innovation/covid-19-innovation/safe-cartridge-system-and-masks)
to use as a starting point for my own design. In the original design, MUSC
recommends using part of a furnace HEPA filter as the filtering material
inserted in a replaceable cartridge system. What I believe was the true key to
their design, however, is the inclusion of a simple one-way valve. The valve
makes it easier to breathe out, prevents excessive CO2 buildup, and extends the
life of the filter, but it does not prevent the user from spreading COVID-19 if
they are already infected.
To speed up the printing process (and thereby the prototyping and
fit-checking stages), I broke the system into three main components:
The mask – this remained untouched from the original
The tube – This component was originally built into the
cartridge, and attaches the filter to the mask. The tube also houses the
one-way valve, which I thought was a particularly high-risk feature, so I
wanted to be able to test it separately.
The cartridge – I needed to replace the HEPA filter
design to fit 5N11 replacements.
Since the mask needed no modifications and changes to the tube were minor, I
was free to focus my energy on creating a cartridge to fit filter replacement
pads. To be honest, even this was a fairly straightforward design job… I took a
few measurements of my filter and made a simple enclosure, making sure that the
tube would fit into the back. One neat trick I employed to check my fit before
printing was that I took a photo of my pad and imported it into my design
software to ensure all my geometry looked correct.
While I originally intended the design to be a snap fit to make it easier to
swap out the 5N11, I decided that simply sealing everything in place with hot
glue, and turning the cartridge into a single-use item would be safer. It is
simply much harder to guarantee a seal if end users are the ones making changes.
The tube only took about half an hour to print, so I made that first to test
the valve. The S.A.F.E. design called for the use of heavier rubber for the
flap, but the only material I had available were thin inspection gloves. Luckily,
the design was robust as-is! However, since my membrane material was much thinner
and tended to curl, I paid extra special attention to ensure the curl direction
defaulted to the closed position. Next, I made the filter cartridge. Since I
had checked all my dimensions electronically before, the parts fit together
perfectly on my first try—yay! I hot glued a filter in place to make sure the
only path for air was through the filter pad itself.
Since the mask took hours to print, I made it overnight. Unfortunately,
sometime in the middle of the night, my nozzle clogged a bit and/or my extruder
skipped a few steps. This resulted in some underextruded and weak layers, which
caused the mask to break as I removed it from the print bed and cleaned up
support materials. However, since the breaks were clean, I was able to fix the
mask in a quick and dirty way by simply smothering the interface with hot glue.
I then attached some rubber material used for sealing windows to the inside of
the mask to ensure I could get a tight airtight seal on my face.
Assembling the mask was simply a matter of attaching the cartridge with tube
into the corresponding hole in the mask. I put the mask on and breathed in and
out to ensure the valve operated as intended. Then, I did a vacuum test—I covered
the filter with a sheet of plastic, and breathed in extra hard… and… success! I
was able to hold the plastic up, demonstrating no leaks in my mask!
Despite some initial success, I quickly realized there were some potential
issues with my mask design. First, the positioning of the filter is non-ideal
for healthcare workers. Although the filter is out of the way for the doctor,
it is facing a potentially exposed area where it is super easy for a patient’s
cough to cover the filter itself. Second, my design lacks any sort of exterior
grating to protect the filter. Regardless, I saw the two units I did make as a
huge success.
As an engineer, I really love designing and making stuff. However, in this
situation, I realized that if any hospitals actually had the real adapters and
respirators to pair with my 5N11 filters, then the filters would be better
utilized as donated goods. I contacted a few hospitals in my area, and UCI said
they could accept them.
Despite giving away my filter materials, not all is lost for me in terms of
making pseudo n95 masks! The NIH actually approved of this design for clinical
use: https://3dprint.nih.gov/discover/3dpx-013429
and both Keck (USC) and Cedars Sinai accept this alternative N95-esque design: https://blog.crashspace.org/covid/
As an aside, now that I have two printers running, my output has tripled (my
2nd printer has a bigger build area than my first), and with bigger
nozzles coming in, I expect my output to increase again to *FOUR* times what I
started with.