Here’s a little eye-opener for you: next time you’re taking a walk, cast your eyes to the ground for a bit and see how far you can go without spotting a carelessly discarded face mask. In our experience, it’s no more than a block or two, especially if you live near a school. Masks and other disposal artifacts of the COVID-19 pandemic have turned into a menace, and uncounted billions of the things will be clogging up landfills, waterways, and byways for decades to come.
Unless they can be recycled into something useful, of course, like the plastic cases used for rapid antigen tests. This comes to us by way of [Ric Real] from the Design and Manufacturing Futures lab at the University of Bristol in the UK. If any of this sounds or looks familiar, refer back to October when the same team presented a method for turning old masks into 3D printer filament. The current work is an extension of that, but feeds the polypropylene pellets recovered from the old masks into a desktop injection molding machine.
The injection molding machine is fitted with 3D-printed molds for the shells of lateral flow devices (LFD) used for COVID-19 rapid antigen testing. The mold tooling was designed in Fusion 360 and printed on an Elegoo Mars MSLA printer using a high-strength, temperature-resistant resin. The molds stood up to the manual injection molding process pretty well, making good-quality parts in the familiar blue and white colors of the starting material. It’s obviously a proof of concept, but it’s good to see someone putting some thought into what we can do with the megatonnes of plastic waste generated by the pandemic response.
The system consists of a small screen that can be worn on the chest or other part of the body, and a lapel microphone to record the wearer’s speech. Using the Deepgram AI speech recognition API running on a Raspberry Pi Zero W, the system decodes the speech and displays it on the Hyperpixel screen.
We’re currently in the midst of New Year’s Resolutions season, which means an abundance of spanking new treadmills and exercise bikes. And one thing becomes quickly obvious while using those machines: the instruments on them are, at best, only approximately useful for measuring things like your pulse rate, and in the case of estimating the calories burned by your workout, are sometimes wildly optimistic.
If precision quantification of your workout is your goal, you’ll need to monitor your “VO2 max”, a task for which this portable, printable mask is specifically designed. This is [Robert Werner]’s second stab at a design that senses both pressure differential and O2 concentration to calculate the maximum rate of oxygen usage during exercise. This one uses a commercially available respirator, of the kind used for painting or pesticide application, as the foundation for the build. The respirator’s filter elements are removed from the inlets to provide free flow of air into the mask, while a 3D printed venturi tube is fitted to its exhaust port. The tube houses the pressure and O2 sensors, as well as a LiPo battery pack and an ESP32. The microcontroller infers the volume of exhaled air from the pressure difference, measures its O2 content, and calculates the VO2 max, which is sent via Bluetooth to a smartphone running an exercise tracking app like Zwift or Strava.
[Robert] reports that his $100 instrument compares quite well to VO2 max measurements taken with a $10,000 physiology lab setup, which is pretty impressive. The nice thing about the design of this mask is how portable it is, and how you can take your exercise routine out into the world — especially handy if your fancy exercise bike gets bricked.
Our canine partners are fortunately not affected by the current global pandemic, but it turns out there are other dangers that might necessitate them to wearing masks: Foxtail seeds. After getting a $400 vet bill for extracting a foxtail from his dog, [Hildeguard]’s ear, [Amos Dudley] decided to take the threat seriously and made her a form-fitting 3D printed mask.
The only commercial solution [Amos] could find was the “OutFox Field Guard”, which is a $50 vinyl-coated mesh bag that covers the dog’s entire head. It had the unfortunate side effects of causing some other dogs to try and rip it off and does not allow easy access to the mouth for treats or balls. [Hilde]’s custom mask was designed in CAD after creating a rough 3D scan of her head with an iPhone app. The bottom is open to allow [Hilde] to freely use her mouth, while the nose and ears holes are covered with mesh. Custom heat-formed polycarbonate lenses cover the eye holes. The mask itself was printed using Draft resin, and the inside was padded with a thin layer of foam. It might also be possible to create a silicone version using a 3D-printed mold. The top features an integrated GoPro mount, and we can’t help but wonder what other electronic upgrades could be fitted to this sci-fi-looking mask.
In the field, the mask worked well and did not seem to bother [Hilde]. Unfortunately, it did not solve the problem of other dogs trying to rip it off at the park, so for the moment [Amos] is only using it for more solitary activities like hiking.
It doesn’t look like [Amos] is struggling in that department, but if you need some help burning of your dog’s energy, you can always built them a 3D printed automatic ball launcher.
Her pattern isn’t a complex cut-out but a simple rectangle, and the trick of sewing them together and flipping them inside out makes for a very tidy result. With three pleats pressed in and the elastic sewn up the result is a mask that’s neat, attractive, effective, and cheap, which is a win in our book.
It’s worth repeating her important point that these are not for use in medical environments, instead they’re the standard street-wear aerosol catchers we’re all used to. This isn’t the first time we’ve looked at masks here at Hackaday, or indeed though [Kristana]’s are by far the tidier neither is it first time one of us has made a mask. We looked at them in depth last year in our surviving the pandemic as a hacker series.
How exactly does salt help? The very fine salt coating deposited on the fibers of a mask’s filtration layer first dissolves on contact with airborne pathogens, then undergoes evaporation-induced recrystallization. Pathogens caught in the filter are therefore exposed to an increasingly-high concentration saline solution and are then physically damaged. There is a bit of a trick to getting the salt deposited evenly on the polypropylene filter fibers, since the synthetic fibers are naturally hydrophobic, but a wetting process takes care of that.
The salt coating on the fibers is very fine, doesn’t affect breathability of the mask, and has been shown to be effective even in harsh environments. The research paper states that “salt coatings retained the pathogen inactivation capability at harsh environmental conditions (37 °C and a relative humidity of 70%, 80% and 90%).”
[Ben’s] build goes above and beyond the usual craft project masks. It uses a laser-cut chipboard frame to fit three HEPA filters, originally designed for the Roomba robotic vacuum cleaner. Two are used for exhalation, while one is used for inhalation. A small blower fan is installed with the intake filter, to provide mild positive pressure when breathing in. The assembly is wrapped up in fabric, using layers of spandex, fleece, and ripstop nylon to provide the best possible seal against the wearer’s face.
It’s a build that should appeal to those who want to breathe cleaner air and also protect others from exhaled particles that can spread respiratory viruses. We’ve seen all kind of masks hit the scene this year; the graphene-impregnated variety is one of the more interesting designs. Still, one can hope that future years lead to less reliance on such measures!