Food Safe 3D Printing: A Study

[Matt Thomas] wanted to answer the question of whether 3D printed structures can be food-safe or even medical-safe, since there is an awful lot of opinion out there but not a lot of actual science about the subject. As a mechanical engineer who dabbles in medical technical matters, he designed as series of tests using a wide range of nasty-sounding pathogens, to find once and for all what works and what does not.

One common argument sprung up from the maker movement response to Covid-19; 3D printed masks and visors. Many of us (this scribe included) printed many thousands of visor frames and ear protectors, using the armies of 3D printers we had available, then distributed them to nursing homes and doctors’ surgeries, and anywhere else that couldn’t get ‘proper’ medical-grade items. There was much opinion about the risks associated with contamination of such 3D printed structures, due to the allegedly porous nature of the prints. [Matt] has shown with some SEM imaging, that a typical 3D print does not have any detectable porosity, and that the grooves due to the layer lines are so positively huge compared to your average bacterium, as to also be irrelevant. Continue reading “Food Safe 3D Printing: A Study”

A Graphene Mouth Screen

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.

An overly damp mask is nothing to sneeze at, so keep yourself in check and keep yourself fabulous.

Continue reading “A Graphene Mouth Screen”