Naomi Wu Raises Safety, Efficacy Concerns Over 3D-Printed Masks in the COVID-19 Fight

As makers, tinkerers, and hackers around the world mobilize to offer aid in combating the spread of COVID-19, noted maker Naomi Wu has raised a note of caution — warning that some ideas being floated may do more harm than good.

With every nation on the planet currently facing a health crisis due to the spread of SARS-COV-2, formerly known as the novel coronavirus, a number of projects have sprung up to fill holes in equipment provision: The Open Source Ventilator project, along with other efforts including those from MIT, Protofy, and Johnny Lee, aim to design low-cost rapidly-producible open-source ventilators to make up a global shortfall in equipment; iFixit is crowdsourcing repair manuals and component information to keep what is already in hospitals running smoothly; and researchers at UMass have created a system for tracking symptoms by listening for coughing.

Wu, however, has raised a note of caution, advising that many makers may be getting carried away in their desire to help — and potentially putting their own health and the health of others at risk, particularly when it comes to 3D-printed face mask designs currently spreading online.

"I have been 3D printing wearables for years. You can 3D print a bikini because your body conforms to the plastic — which is flexible but not really soft," Wu tweets. "The bones in your face don't conform this way. A TPU mask is not soft enough to create an airtight seal.

"N95 air filters have significant resistance. If you don't have an airtight seal you will just be sucking in air from the sides of the mask and basically have a cough shield/surgical mask. Except plastic does not absorb droplets so you're left with a wet mess strapped to your face. 3D-printed masks are not a useful thing at the moment."

There are personal risks, too, beyond producing equipment which isn't fit for purpose. "This is a DIY PAPR [powered air-purifying respirator]," Wu writes in a separate thread, posting images of a full-face snorkel mask which has been linked to a filtered air pump and is another of the designs being investigated by the maker community. "HEPA filtered air is blown in under pressure, exhalation passes through a check valve and is directed out the P100 3M filter. Potentially for high-risk environments [but] testing it without a CO2 sensor is also a good way to kill yourself."

Other unpowered mask designs are equally dangerous for the wearer, Wu argues: "N95 mask material has a fair amount of air resistance - so the masks have a large surface area. Trying to breathe through a little disk of N95 material is like trying to breathe through a straw. But it gets worse - you have to try and exhale through the same little disk of material. This results in CO2 build-up. After about 30 minutes your plastic mask, if actually airtight and strapped securely to your face will, before you can take it off, kill you - very peacefully. You'll just slump over and go to sleep, but you'll still be dead."

Wu does have some suggestions for things makers can do to aid in the fight against COVID-19, though: "Given the desperate shortage of PPE for clinicians, and the surplus in time most of the public now has — it makes sense to reserve paper surgical masks and N95 masks for first responders and clinicians, and for the public to use cloth masks washed and changed at regular intervals.

"A sewing machine is a formidable home machine tool — and possibly the best one we have to fight this. Sew masks and PPE. Print face shields and vent splitters on request. That's what we've got right now."

All of Wu's advice can be found on her Twitter profile; meanwhile, she has also linked out to a Prusa design for a 3D-printed face shield and a sewing pattern for a washable cloth mask.