As a scientist, researcher, teacher, and RPG nerd, I am really dependent on printers, long before being a ‘maker‘ with a 3D printer was the new hotness. However, I must admit that I don’t really know how they actually work, and I don’t think about it too much as long as actually works. Laser printers have become much more affordable for home users (although mind the price of toner, the costs build up over time), but I don’t really care if it’s laser or inkjet, I’ve got Featured Articles and the occasional character sheet to print!
Now it turns out that scientists that specialize in electronics and circuitry have been dinking around with inkjet printing in order to make the circuits they need on-demand. This works because inkjet printers literally shoot ink at paper (so now I know how they work – the things you have to learn when blogging, huh?), and some inks are conductive, which means they can carry electric currents across a circuit. ‘Printing’ a circuit isn’t an entirely new thing – there are even kids’ projects for drawing circuits with a pencil, of all things. Turns out all you need is carbon, which is nice and cheap.
The neat thing about printable circuits is that with the right printing materials, you can get circuitry that could be printed on, or even stuck on, any kind of surface. But what about circuits that you could print and stick onto a highly flexible, but uneven surface? Imagine printing a circuit less thinner than a sheet of paper stuck onto an organ that will flex along with it without causing you a lot of discomfort as it takes measurements of your vitals. That’s what the authors of this week’s Featured Article proposed with their design, which they tried on gummi bears. You heard that right, and that explains the Featured Image.
The authors’ literature review reveals that this isn’t new stuff – there is already some research out there on putting circuits on a brain, of all things (bringing us closer to a few sci-fi ‘augs‘…?). The big concern when it comes to sticking things on an organ – or really anything inside the human body – is simply put: they don’t belong there. Something like a rigid circuit would trigger immune responses and cause all sorts of havoc in the human body because after all, something’s not right. Organs are especially sensitive to this, since they made of rather delicate material as it is. They are essentially ‘hydrogels,’ a network of material that contains a considerable amount of water. You can imagine that all that water would make organs highly flexible, but the water contains all sorts of salts that may disrupt the operation of an electrical circuit, to say nothing of the damage to cells that make up the organ.
Relax, that’s not a real heart (hopefully), it’s made of gelatin. To be fair, that’s not too much of a stretch from the real thing. Anyway, without going into too much detail (this is a very casual blog – if you want more details or you’re a materials scientist yourself, read the OPEN ACCESS article), the authors had to take a lot of design matters into consideration. For starters, they had to mess around with the carbon-based ‘ink’ so it won’t dissolve once it’s been printed and stuck onto the organ of choice – not like they’re trying to make temporary tattoos on a pancreas or something. They settled on printing the circuitry in layers with their altered inks. To test how well it works, they measured its electrical signals on cells similar to those in heart muscle, which is quite dependent on electrical signals and a good candidate for any kind of vital measurement, really. In addition, they printed it on other kinds of hydrogels, including agarose and melted gummi bears. The latter might seem like a ‘fun’ project, but there’s logic here: as mentioned earlier, gels in the human body are made of water and substances like sugars, salts, fats, and proteins. Haribo gummi bears (yes, they are required to declare brands in case anyone wants to replicate this study)…well, just read the ingredients. Seems like a good analog. In addition, according to the authors, gels (like gelatin) are often used as scaffolding material for repairing tissue damage. Little wonder why there’s a lot of ‘healing gels‘ in sci-fi, yeah?
So how well did their printed circuits work? Their circuits had about the same performance in measuring electrical signals as other printed circuits on the same kinds of cells (see what I meant about replication?), but bear – I’m sorry *snrk* – in mind that the circuits in those studies used gold, and you know that gets expensive. So at the least, Adly et al. made flexible circuits that are easier and cheaper to make with similar effectiveness, so that’s good for disposable circuitry. The simple fact that they got these circuits to work on non-living gels (unless you believe that gummi bears are life – maybe you should see a nutritionist?), the authors attest, means that they could give gels better functionality when used as part of a tissue or organ repair. Good stuff that I’m sure will save a life someday, and here I am thinking of my pulled hammy after an impromptu 5K run yesterday. I can’t think of any other way of getting Dratini candies, OK!?
So there you have it – material scientists with inkjet printers can now print circuits that you could stick directly onto organs or ‘healing gels’. There’s still a lot of workup to be done on the ink so it won’t disrupt the everyday operation of your internals, but at least it doesn’t have to use heavy metals like gold, which can cause poisoning if it leaches into your bloodstream. Carbon might be a bit more agreeable. Something to think about the next time you’re snacking on some gummi bears, although the more paranoid among you will probably start checking for printed circuits on your snacks…
(relax, if you end up swallowing carbon, it may as well end up in your gut for a while, not unlike how other ingested poisons are treated)
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Featured Article: Adly N, Weidlich S, Seyock S, Brings F, Yakushenko A, Offenhäuser A, Wolfrum B. (2018) Printed microelectrode arrays on soft materials: from PDMS to hydrogels. npj Flexible Electronics 2(15) DOI: 10.1038/s41528-018-0027-z
Featured Image: Public Domain (Author: Esther Merbt, 2014)