Can anything useful be painted on with this? I don’t know squat about electronics, but I think that this is like having wires but no other components (resistances, transistors, logic gates).
So any chance of making something really geeky and cool with this?
Could you, for example, fashion some kind of ID tattoo from it that you touch and lets you in?
bump?
I thought this would meet a lot more interest than zero.
Conductive ink has been around for a while. It’s nothing new. This is the first time I’ve seen a “skin safe” version, though I can’t say if previous versions that I’ve seen have had any effect on the skin or not. Conductive ink is used to “print” circuits onto paper or plastic film, which is used for all sorts of things. Conductive ink is sometimes used to seal up holes in RF shielding, and it is also used to create things like membrane switches and RFID tag antennas.
I don’t know how well the ink works in a tattoo type application. If the ink particles aren’t touching the tattoo won’t be conductive, and it is my (possibly faulty) understanding that the reason tattoos are permanent is because clear cells surround the ink particles under your skin and form a mostly permanent structure with the ink trapped inside.
Yeah, I did notice that this was brushed on and not tattooed. So these would not be permanent.
Still, is there anything even remotely cool that could be done with this? When they print circuits in paper or plastic film, what do they use them for?
Would you need to get resistors and transistors as piercings to make something useful?
You could really screw with an E-meter.
Make your own Tron suit?
Get some conductive glue as well, then go crazy sticking surface-mount components to yourself. 
I think the piercing idea shows a lot more commitment to geekdom.
Actually, on re-reading that article I found out it is magnetic ink, not conductive ink, that they use on checks.
Maybe you can make a Hieronymus machine?
Depends on how permanent the glue is, doesn’t it? 
Besides, using piercings as circuit components may run into conductivity issues in the salty liquid interior of the body. You’d have to insulate them at least. Though if you wanted to connect to nerve fibres, you could experiment and create a low-budget version of 'trodes. Though if that went wrong, you’d end up a wirehead.
I’ve taken apart calculators and digital cameras where the circuitry was on plastic and just curled into place between retaining pins.
I could see having some fun with this ink and some SMD LEDs. Would certainly be the talk of the office Christmas party
If you paint it on yourself, perhaps an orchestra will let you stand up in front and, you know, conduct.
The wires themselves could serve as resistors, if thin/long enough. Similarly for capacitors. And yeah, you could stick some transistors to yourself somehow, but I think the real problem would be the lack of layers. Printed circuit boards have multiple layers and vias to connect between them. Without that, you’d be very limited in what you could create, simply because the wires can’t cross on a 2d surface without touching.
I guess you could easily do layers with some other insulating paint (white elmer’s glue?)…
So we have (potentially) resistors and capacitors. Any fun project that could be done with just those?
Use Band-Aids…
But really, the whole idea is pretty ridiculous.
On a sphere. If you were willing to hold your palms together you’d be a torus, and if you put your hands on your hips (knees in tight optional) you’re genus two.