During this entire pandemic, as people who own 3D printers are eager to put their tools to use, there has been an argument happening. Can a 3D print be properly sterilized for reuse after potential exposure to the Covid-19 virus? Luckily, Prusa Printers have been pushing hard and are getting real results from three independent labs.

What is the problem?

3D prints from a filament based machine like most people have in their homes are porous. There is a little confusion around this fact sometimes, where people think that “porous” is referring to improper layer adhesion, water tightness, or air gaps in the infill. This is not the case. The additive layer structure of a 3d print presents tiny crevices in which things like bacteria and viruses can hide, and even theoretically withstand sterilization procedures. These crevices can be microscopic in scale, so no matter how great your 3d print looks, or how fine you’ve sanded it, this is still a problem.

Hospitals typically use high temperature to sterilize things, because even some medical tools can have very fine crevices. High temperature in an autoclave will sterilize even the most porous structures. However, 3D prints, being plastics that become malleable at relatively low temperatures have a tendency not to survive autoclaves. They deform, which is a nice way of saying that they melt to some degree and change shape.

What about other methods of sterilization?

Yes! There are other methods such as chemical sterilization, steam sterilization, and UV-C sterilization. Each presents its own questions that require testing to know exactly how effective they would be on 3D printed goods. For example: Can UV-C reliable sterilize into the microscopic crevices present in all filament based prints? Do the chemicals we use to sterilize degrade the material in an unsafe manner? All of this has to be thoroughly tested to be able to use them in practice with confidence.

Prusa’s results:

Testing is exactly what is happening in the Czech republic. The Prusa team has been pumping out face shields like crazy. Those face shields have 3D printed parts that require sterilization or disposal after exposure to infected patients. If they can be sterilized and reused, that would be incredibly helpful. So, there is actual testing being done by three independent labs to confirm what works and what does not work. All of this is printed with PETG filament.

It is important that you go to the page on Prusa’s website for the latest version of this data. This study is ongoing and any data included in this article may be out of date.

First, we have what is not recommended. As you can see, there are not big surprises here. Heat and 3D prints generally aren’t a good mix.

Here is the result chart (click through to see the latest version). Note that the tests are verified by independent labs with links to their research. Many of these were tested with actual Covid-19 itself to ensure that the results are immediately relevant.

So, we can definitively say that this is how you can sterilize a 3D print, if you replicate the exact methods presented here. And, one more time, be sure to visit Prusa’s page for all the up-to-date results and notes.