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!
With all the cool and useful parts you can whip up (relatively) quickly on a 3D printer, it’s a shame you can’t just print a PCB. Sure, ordering a PCB is quick, easy, and cheap, but being able to print one-offs would peg the needle on the instant gratification meter.
[Peter Liwyj] may just have come up with a method to do exactly that. His Instructables post goes into great detail about his method, which uses an Elegoo Mars resin printer and a couple of neat tricks. First, a properly cleaned board is placed copper-side down onto a blob of SLA resin sitting on the print bed. He tricks the printer into thinking the platform is all the way down for the first layer by interrupting the photosensor used to detect home. He lets the printer go through one layer of an STL file that contains his design, which polymerizes a thin layer of plastic onto the copper. The excess resin is wiped gently away and the board goes straight into a ferric chloride etching bath. The video below shows the whole process.
As simple as it sounds, it looks like it works really well. And [Peter] didn’t just stumble onto this method; he approached it systematically and found what works best. His tips incude using electrical tape as a spacer to lift the copper off the print surface slightly, cleaning the board with Scotchbrite rather than sandpaper, and not curing the resin after printing. His toolchain is a bit uncoventional — he used SketchUp to create the traces and exported the STL. But there are ways to convert Gerbers to STLs, so your favorite EDA package can probably fit in to the process too.
We are all intimate with face coverings to slow the spread of the coronavirus. Some are reusable, and some become waste after one use. [Dr. Ye Ruquan] and a research team from City University of Hong Kong, CityU, are developing an inexpensive reusable mask with outstanding antibacterial properties, and, get this, the graphene it contains will generate a tiny current when moistened by human breath. There isn’t enough power to charge your phone or anything, but that voltage drops as the masks get dirty, so it can help determine when it needs cleaning. The video after the break shows the voltage test, and it reminds us of those batteries.
All the remarkable qualities of this mask come from laser-induced graphene. The lab is producing LIG by lasering polyimide film with a commercial CO2 infrared model. In a speed test, the process can convert 100cm² in ninety seconds, so the masks can be made more cheaply than an N95 version with that melt-blown layer that is none too good for the earth. Testing the antibacterial properties against activated carbon fiber and blown masks showed approximately 80% of the bacteria is inert after 8 hours compared to the others in the single digits. If you put them in the sun for 10 minutes, blown fabric goes to over 85%, but the graphene is 99.998%, which means that one bacteria in 50K survives. The exact mechanism isn’t known, but [Dr. Ye] thinks it may have something to do with graphene’s sharp edges and hydrophobic quality. A couple of coronavirus species were also affected, and the species that causes COVID-19 will be tested this year.
The realities of wearing a mask when you go out, from forgetting the thing in the car to dealing with fogged up glasses, have certainly taken some getting used to for most of us. But not every issue is immediately obvious. For example, experts say that as a mask gets damp from exhalation or perspiration it becomes less effective. Which is precisely why [Rick Pannen] has designed the Mask Moisture Meter.
As deep as we are into the Microcontroller Era, we really appreciate the simplicity of this design. It’s just a 555 timer, a buzzer, some LEDs, and a handful of passive components to get them all talking to each other. There’s no firmware or programming required; just put a fresh battery in the holder and away you go. The traces of the PCB serve as a moisture detector, so when the board is pushed against something wet enough, the red LED and buzzer will go off to warn the user.
Now admittedly, there’s a point where you certainly won’t need an electronic gizmo to tell you a mask is wet. But as [Rick] demonstrates in the video after the break, the circuit is sensitive enough to indicate when there’s moisture in the material that might not be immediately obvious to the eye.
If you have worn a mask and glasses together for more than a quarter of a second, you are probably annoyed that we don’t have a magical solution for foggy lenses. Moisture-laden air is also a good indicator of where unfiltered air is escaping. Most masks have some flexible metal across the nose bridge that is supposed to seal the top, but it is woefully inadequate. The Badger Seal by [David Rothamer] and [Scott Sanders] from the University of Wisconsin-Madison College of Engineering is free to copy during the COVID-19 pandemic, even commercially. It works by running an elastic cord below the jaw and a formable wire over the nose to encourage contact all around both mouth and nose.