A friend of mine and I both have a similar project in mind, the manufacture of custom footwear with our hackerspace’s shiny new multi-material 3D printer. It seems like a match made in heaven, a machine that can seamlessly integrate components made with widely differing materials into a complex three-dimensional structure. As is so often the case though, there are limits to what can be done with the tool in hand, and here I’ve met one of them.

I can’t get a good range of footwear for my significantly oversized feet, and I want a set of extra grippy soles for a particular sporting application. For that the best material is a rubber, yet the types of rubber that are best for the job can unfortunately not be 3D printed. In understanding why that is the case I’ve followed a fascinating path which has taught me stuff about 3D printing that I certainly didn’t know.

A friend of mine from way back is a petrochemist, so I asked him about the melting points of various rubbers  to see if I could find an appropriate filament His answer, predictably, was that it’s not that simple, because rubbers don’t behave in the same way as the polymers I am used to. With a conventional 3D printer filament, as the polymer is fed into the extruder and heated up, it turns to liquid and flows out of the nozzle to the print. It ‘s then hot enough to fuse with the layer below as it solidifies, which is how our 3D prints retain their shape. This property is where we get the term “plastic” from, which loosely means “Able to be moulded”.

My problem is that rubber doesn’t behave that way. As any casual glance at a motor vehicle will tell you, rubber can be moulded, but it doesn’t neatly liquefy and flow in the way my PLA or PET does. It’s a non-Newtonian fluid, a term which I was familiar with from such things as non-drip paint, tomato ketchup, or oobleck, but had never as an electronic engineer directly encountered in something I am working on.

A Newtonian fluid has a linear relationship between shear stress and shear rate. That’s dry language for saying that when you press it, it moves, if you press it more, it moves more, and the readiness with which it moves, or its viscosity, is the same across all pressures.

I’m used to viscosity, having run all manner of dodgy old cars I’m particularly familiar with selecting the correct oil by viscosity figure. A non-Newtonian fluid doesn’t have this linear relationship, and its viscosity changes with pressure. For example the non-drip paint has a high viscosity until you press it with a paint brush, at which point its viscosity falls and it becomes liquid enough to spread around. Rubber does this too, and were I to attempt to squeeze rubber filament through my extruder, it would become very viscous and block it up. The closest thing to a rubber I could reasonably use is TPU, or Thermoplastic PolyUrethane, but as you might guess from its name, it’s not a rubber in the same sense as the rubbers I’m looking at, even though it’s what many people use for shoes. It’s flexible, but not grippy.

So if rubber is non-Newtonian and I can’t print with it, how do they mould it? An online search finds specialist plants for rubber extrusion and moulding so it’s possible, but in fact those rubber moulded items you’re familiar with won’t be made with liquid rubber. Instead they press shredded rubber into a mould and heat it so that it fuses, resulting in a moulded shape. I was fascinated to find that the process doesn’t require excessive temperatures, though whether that makes it achievable in a hackerspace is yet to be determined. Has anyone out there experimented with real rubber? Meanwhile I have those multi-material uppers to work on.

This administration is in the midst of failing the American people in so many ways, of course, but if you need one stark example of that failure then you can find it in measles. When I wrote this post way back in March of this year, it was our first Techdirt post done on the disease in over 11 years. In other words, this is how it started:

And from there we were off and running. It took roughly a month for us and many others to begin warning what would be inevitable if RFK Jr. wasn’t axed from his role as Secretary of Health and Human Services. A virulent anti-vaxxer leading the charge on a measles outbreak was always going to result in a lackluster response at best, but the real embarrassment would come in the form of America losing its measles elimination status. That status was hard won in 2000 via a concentrated and government led vaccination campaign beginning in the late 70s and early 80s. 12 months of continuous spread from connected outbreaks loses us elimination status and we began predicting this would happen eight months ago.

So that’s how it started. How are we looking at present? We now sit at 2,012 confirmed cases of measles in America for 2025. And those numbers are both incomplete for the year and almost certainly significantly underreported. Add to that the fact that we are enduring current outbreaks in multiple states and we are set up for a banger of a 2026.

Measles cases nationwide have reached 2,012, the Centers for Disease Control and Prevention (CDC) reported last week, as outbreaks in Arizona and South Carolina continue to grow and three other states alert the public about airport exposures.

The US total reflects 54 new cases, as the country teeters on the brink of losing its measles elimination status—which it earned in 2000—next month. This year’s total is the nation’s highest since 1992, when officials reported 2,200 cases. Coordinated vaccination efforts led to a precipitous drop in cases in the ensuing decades, but vaccine skepticism in recent years has spawned the disease’s resurgence.

In those numbers are 3 deaths, including two children, and 227 hospitalizations. More frightening is that, while 93% of infections have occurred among the unvaccinated, 7% have not, including 4% that had two MMR vaccine doses. That sure sounds like we’re experiencing an increase of breakthrough infections, which itself is an indication that we are losing herd immunity protections.

So it’s not really a question of if we’re going to lose the measles elimination status. The game is already over, we’re just waiting for the clock to run out. The real question is whether that embarrassment is going to spur anyone in positions of power to do anything about it. And the only real thing to do here is get RFK Jr. the hell out of his cabinet secretary role.

Bobby Allyn, reporting three weeks ago for NPR:

The developer of ICEBlock, an iPhone app that anonymously tracks the presence of Immigration and Customs Enforcement agents, has sued the Trump administration for free speech violations after Apple removed the service from its app store under demands from the White House.

The suit, filed on Monday in federal court in Washington, asks a judge to declare that the administration violated the First Amendment when it threatened to criminally prosecute the app’s developer and pressured Apple to make the app unavailable for download, which the tech company did in October. [...]

To First Amendment advocates, the White House’s pressure campaign targeting ICEBlock is the latest example of what’s known as “jawboning,” when government officials wield state power to suppress speech. The Cato Institute calls the practice “censorship by proxy.”

Good on developer Joshua Aaron for filing this suit and defending his work.