How your perfume is like a discontinued Canadian drink

I’ve been brushing up on aerosols lately.  In the course of job hunting, I found an open position for an aerosol researcher at one of the DOE national labs (looking for: chemist, chemical engineer, or atmospheric scientist…take three guesses for what they’re working on).  My first instinctual answer to “What do I know about aerosols?” was a whole lot of nothing.  Spraypaint, right?  And PAM?  Somehow I doubt that’s enough for a successful application.

But the more I thought about it, the more I think I actually know, or at least could translate from parallel science, about aerosols.  I mean, they’re essentially a suspension of solid or liquid particles in a fluid right?  Here, of course, I’m using the broader-than-my-elementary-school-lessons and defining a gas as fluid (the 10 year old that still lives in me is shouting “Nuh-uh! Three phases: solid liquid and gas!”).

Because my brain has been in science writer mode lately, it started working through analogies.  How could I illustrate an aerosol?  Then it hit me – there’s already a not-so-terrible hands on macro-scale analogy for the micro-sized aerosols:



If you’re old enough to remember Orbitz (and hopefully not cosmopolitan enough to have tasted it), you’ve seen a hands on model of an aerosol!  If you don’t remember, be thankful, and then take a look above.  There it is in all its glory!  A handful of small, squishy, sweet  particles dispersed through a fluid (which we can pretend is the fluid of air).  That right there is a simple proverbial ball-and-stick model of clouds, perfumes, spray paint, pollen, and volcanic ash.  Of course, the difference between a cloud, a dust storm, and Lady Gaga’s blood and semen perfume is all in the details.  There are some chemical details (how the particles or droplets interact with another and their environment, often through hydrogen bonds or van der waals forces), some physics details (gravity, the flow of the fluid/air around the particles), some geometric details (how closely those particles are packed together, how they’re shaped).  But for a simple model?  It’s all in one debatably tasty beverage.


Exciting baby-saving technology! Boring 3D printing.

By now you may or may not have heard how a 3D printed tracheal splint saved the life of an infant on the verge of having a collapse of the trachea. There are so many kinds of awesome in this story! (TIME writeup here; original paywalled writeup here.) 

The stent was custom designed and printed at the University of Michigan for the specific anatomy of the baby and served (as far as I can tell) as a sort of last ditch Hail Mary for fixing the problem. Digital designs of the trachea and splint were assembled, a biocompatible polymer was printed from those blueprints, and a life was saved.


Image from Dr. Zopf and team’s report in the New England Journal of Medicine, linked above. Not just printing splints, but tracheas too!

For the baby (and for the rest of us who may need some custom-fit medical TLC), this is an amazing use of 3D printing. It’s a perfect example of why every medical institute and hospital should have a 3D printer. But as a posterchild for the technological potential of 3D printing?  I can’t help but feel it’s kind of lame.

See, the stent was printed from a single semi-rigid material – polycaprolactone. Yawn, been there. Printing a single polymer ain’t that impressive anymore. Hell, folks have been doing this since before the marketers ever started calling it 3D printing (just one example: 

Popular internet disclaimer here: I am not a doctor. But here’s what I imagine the priorities are for a splint:

  1. Mechanical stability (“Hey splint, hold my trachea open please? Got it? Not gonna drop it on your toe in a few seconds? Great!”)
  2. Bio-compatibility (Cells aren’t exactly the sharpest cards in the deck. They may not realize that crazy thing which was just jammed in your neck is actually saving your life instead of, say, being any other number of things that are not so beneficial when jammed in a neck which require immediate removal please.)
  3. Degradability (Remember as a kid outgrowing your favorite t-shirt but trying to squeeze into it anyway, often with dramatic seam-rippage? Now imagine a stent squeezing down on your trachea like that after it grows. No thanks.)

We’ve been doing stents and splints for a long time. We’ve figured out how to hit those priorities quite well. The real exciting news here is time and customizability. The fact that the doctors have access to a 3D printer which could print a stent exactly matching the infant’s anatomy faster than they could get one traditionally made is awesome! Tech with a low barrier to entry (cost, complexity, etc.) having a significant societal impact is always a good thing.

But just printing a biodegradable plastic splint is not terribly impressive. There’s not a whole lot technologically interesting here. More often than not, the rallying cry I hear around 3D printing centers around printing any object you could conceivably want. And that’s simply not achievable now. What makes something a table or a sponge or a computer isn’t just a shape (I would be remiss not to mention cargo cults). It’s the materials used to make them. 3D printing has great control over shape. It has terrible control over materials.

Cago cult plane

“Pilot to tower: I feel like I’m flying a bundle of wood up here!”

Maybe this is just the jealous materials scientist in me talking.  “Guys, there are all these crazy wild materials and composites you could start printing!  Pretty pretty please?” Making, say, a squishy stretchable biocompatible doodad with integrated electronic components is really hard from a conventional manufacturing standpoint. It requires at least three different classes of materials needing to be combined and assembled in intricate ways with high spatial fidelity. We’ve got all of these materials, and we know they can be 3D printed. So why are we still stuck with simple rigid mechanical scaffolds and hobbyist parts? The hard science is done. All (ok, maybe most) of the details you could likely want about the print-ability are already out in the scientific literature right now. Further studies on the fundamental science are going to be few and far between. “It’s an engineering issue,” I can hear the NSF respond to your 3D printing grant proposal as they decline funding.

I’ve read a lot and interviewed with some 3D printing companies, often in job hunting mode (yes 3D printing dudes and dudettes, I’ve asked some of you for jobs). None of them seem to be thinking about materials in any meaningful way, as far as they’re willing to talk about. Which is a shame, because the platform is itching for it. “Yeah, we want to make squishy things and electronic things and biological things!” they say. But then you ask how, and they get fuzzy on the specifics. And by fuzzy, I mean THERE ARE NO MATERIAL SCIENTISTS ON YOUR TEAM WITH THE LEEWAY TO DO ANYTHING INTERESTING. There are one or two exceptions. Stratasys, for example, seems like they’ve got their heads on right for the long term. The other guys? Unless they really start thinking about composites, and multi-material printing, and moving away from ABS, there’s going to be a long slide into stagnation and exclusive appearances on Etsy jewelry sites.

Make it so, Number One!

Captain Picard would probably replicate a whole lot less Earl Grey if it came out as a cup full of plastic.


Anyway, all of the above is small potatoes: a bit of nitpicking and cynicism about the reporting around 3D printing I’ve seen. Because I absolutely do not want to overshadow the real fantastic headline here: Science – Now saving babies faster and better! If the worst 3D printing can do is save lives, I think we’re in pretty great shape.

‘Science cafes’ feed hunger for technical understanding

Shameless self-promotion time!  It’s my first freelance piece, talking about local science cafes.  Print newspapers are the way of the future, right?

What I do find kind of interesting is all my science friends who I’ve linked this to.  There’s been a lot of surprised excitement when they find out that there are, in fact, science cafes near them.  There’s probably one near you too.

What to do with all this carbon?

It’s been a tough week for carbon.  First Bayer (best known for making quite a wide range of drugs and diagnostics) announced that their materials science subgroup was shuttering its carbon nanotube research project.  And then a Czech/Singapore research team published an article about the unsung difficulties of making graphene (RSC writeup and summary here), essentially saying “yeah, this common way of making graphene actually leaves you with a whole mess of unpredictable side products and defects”.  Not something you want in an electronics-grade material.

Carbon nanotubes and graphene are two sides of the same coin, in which a specific bonding pattern in carbon lends it semiconducting and conducting properties.  Where graphene tends to be thin, flat, large(ish) sheets of conductive carbon, the nanotubes can be thought of like cylinders made by rolling up those sheets.  They’re pretty cool materials, with all sorts of promise for cheap, flexible, transparent electronic applications.  Carbon, after all, is much cheaper than a lot of the noble metals that get used as electrodes. 

Folks have been heralding the Coming of Nanotubes for years now.  It’s one of those techs that perpetually seems 10 years away.  Carbon nanotubes have been imagined in all sorts of applications (hell, the topic even has its own wiki), from continued electronic miniaturization, to medical diagnostics and delivery systems, to mechanical reinforcements.  At the just-crazy-enough-to-maybe-work end of the spectrum, carbon nanotubes have been proposed as a material potentially strong enough for an eventual space elevator.  And the discovery graphene, of course, won the Physics Nobel a few years back, which I was a bit skeptical about.

ImageOne of the few things packed with carbon nanotubes that you can actually go out to a store, right now, and buy.  Photo from BNC and


So the fact that more folks, especially ones as established as Bayer, are coming out and saying they don’t know what to do with this stuff isn’t terribly comforting.  But I’m not too worried for carbon.  Graphene (and to a lesser extent carbon nanotubes) are new enough, and sexy enough, that they’ve still got a lot of money and research flowing to them.  That buys a lot of good will.  Put a little more cynically and colorfully by a friend of mine, “You could spit on a sheet of graphene and get 3 publications out of it.”  So I’d say that graphene/spit composites are something we can all be excited to see within maybe 10 years.