Researchers create rollerball-pen ink to draw circuits | Hacker News Reader

Researchers create rollerball-pen ink to draw circuits

physorg.com

46 pointsph0rque21 comments

Conductive pens are already available and used for circuit board repair (I think resistance is too high for long traces), e.g.:

  http://www.circuitspecialists.com/8420-p.html

If you check the PCB forums, people are always toying with the idea of hooking these up to a plotter for DIY circuit boards without needing etching chemicals.

Presumably these researchers have come up with a better one (probably more consistent flow).

Seems many people are jumping on the "been doing it for years" bandwagon. Since I've never touched this stuff, I have questions: do the existing conductive pens work on paper? Can you take notebook or drafting paper, apply the existing conductive pen "ink" and get a functional circuit of reasonable size (up to the size of the paper) without burning up the paper?

You mention that perhaps the resistance is currently too high and that these guys may have come up with something that has "more consistent flow."

The news here is ink-on-paper makes circuits, not conductive pens have been invented for the first time.

The existing pens are intended only for minor PCB repairs. They are terribly expensive, as in $100/oz, have high resistance, and cannot be drawn with smoothly (like a pen). They are also not intended for the kind of flexing that you see on a piece of paper.

Example (0.3oz for $30): http://www.amazon.com/gp/aw/d/B000B5YDT8

Historically, you've been better off using conductive silver thread for flexible and on-the-fly circuits. Still expensive and resistive, but tolerably so.

Example (82 ohms/ft, $5/yd): http://www.sparkfun.com/products/8544

They can be found for around $30/oz; the first google shopping result for "conductive pen" is 9 grams (0.317 oz) for ~$10. It seems to be the same one you linked to on amazon (is that the mobile version, by the way? Because there's practically no information on that page and it looks horrible).

The cheaper $/oz is for nickel-based pens. I haven't ever encountered a nickel pen in person. Do they work as well as the silver-based?

A big part of this is the more consistent flow, yes. Two of the major factors in the ink design were balancing the viscous properties of the ink (mildly shear-thinning, iirc) with the need to keep the silver nanoparticle concentration as high as possible.

(Disclaimer: I am a former member of the Lewis group, but didn't work on this project myself.)

Do you know if they are also much more cost effective than existing pens ?

No idea, as no commercial-scale production has been attempted. This is all still lab-scale.

It appears to handle reasonable amounts of current, it can drive an LED over about 10" of trace in the LED grid example. That example also has cross overs, though they don't mention it in the article.

I wonder how they bond the components to the traces. Is setting them on fresh ink sufficient?

Binding components to the traces (or even keeping them on the paper) is definitely my biggest area of curiosity. Putting a lil-dab-o-glue on the bottom would certainly be problematic as it would spread to insulate the connections. Components with adhesive surfaces would solve the problem of sticking it to the paper but not the problem of binding to the trace path. I have no ideas how that would work.

I used to work in the lab in question, though nowhere near this project. (And I'm ridiculously proud of my colleagues right now. :D )

To answer your question, setting the components on fresh ink is often sufficient but not always. IIRC, components were often put in place and then "drawn over" a second time with the pen, or small beads of ink were put in place.

I saw cross-overs demonstrated simply using normal white-out (!) after the first trace was dry, but I no longer have access to a journal subscription so I'll have to bug my colleagues for a copy before I know if that is what was used in the publication.

use other side of paper? tape one piece of paper over the other line?

This has given me an idea: an etch resist pen in a plotter-like setup. It's about time I use the steppers i pulled out of old Epson printer and use up some of my copper-clad boards.

This struck me as non-novel since the CircuitWorks pens have been around for a while. But the ability to write on a flexible medium and bend it etc is the news here.

There are a number of uses for something like this, if its economical. I hope they can commercialize it.

Nothing that couldn't be done with 30's era conductive paint.

granted you have to use a small brush to apply...

...and i still think "soldering" leds to a piece of paper is ... wrong.

There's already the paper-based mobius circuit: http://www.evilmadscientist.com/article.php/mobiuscircuit

This seems awesome. They neglect to mention how to power any circuits and what components you could and how. If this could be perfected though, Electrical Engineers would slowly take over the world... with circuits....

They already did.

:) It's nice to hear we are appreciated.

Great, now they just need to stock compatible napkins in bars. "hey, I've got this idea... Look, it works!"

Always carry a few LEDs and resistors in your pocket!

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