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Xerox recently announced a new conductive ink that will allow for flexible printed ICs which are stable in open-air environments -
Xerox's process uses ink containing silver metal that can be used to wire up processing circuitry. It works on surfaces such as plastic that earlier have shown an inconvenient tendency to melt under the high temperature of liquid silver; Xerox's process works with an ink compound with a much lower temperature, the company said.[Thanks, Andy!]
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The technology uses conventional inkjet printing methods, and though Xerox has used it with conventional desktop printers, the company expects that it would use continuous-feed printers that print on rolls rather than sheets of material. It doesn't require the super-clean environments needed for conventional silicon chip manufacturing. The Xerox process actually requires printing three layers on a substrate: a semiconductor, a conductor and a dielectric. The silver ink is the layer that conducts electricity.
This might just be that special sort of bullet to make the printable solar cells really take off.
Unfortunately, silver is already heavily consumed as an industrial material. Is there anything special about silver that makes it viable for their ink in a way copper or aluminum couldn't be?
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@JCoyote - I could only assume the answer is yes
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So if I understand this - the process will likely not help the amateur/hobbyist, as printing a PCB circuit for us hacks requires later soldering - which would likely destroy the plastic/medium it is printed on no?
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Depends on the plastic. If it's printed on a heat-resistant material like Kapton (which is what flexible circuit boards are made of) then it would be fine. I'm more worried about vaporizing or otherwise destroying the silver itself...
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As I understand it, if the inks are compatible with consumer grade printers we have available, this could mean we could be printing our own ICs! I imagine some sort of small clamping mechanism could be employed to create pins/terminals which could in turn connect to a solderable socket.
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You would use a conductive epoxy rather than soldering. So your projects would go to SMT rather than through hole. You may gain some advantage over the typical subtractive process using hobbyist methods of quick release, iron-on, toner transfer systems. But the move to SMT creates tougher layouts since you can only escape from a package on one side without using vias or the legs of DIPs.
Using DIPs and other through hole devices provide natural, conductive paths between sides without the need to make true, through-hole vias. So you are still in the business of needing to drill holes. It is exciting though. I wonder how the current rating compares to 1/2 oz copper?
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This should not be made out to be some new thing. Two years ago I was working for a company in the Pacific Northwest that was one of several companies in the United States secretly testing "nanoprinting" technologies. I designed test circuits with lines of varying widths, made plates from these, then we did the printing and conductive tests. I was never privy to the specifics of the results except that we were successful at getting good conductivity with printed circuits.
I'm able to talk about it only because they kept saying I was going to have to sign a non-disclosure agreement, but in October 2007 I left the company, and they had never actually had me sign anything!
The ink we tested, BTW, was invisible. We added a bit of metallic ink to it in order to make it visible. Had we not added it, it would have been impossible to see the circuitry with the human eye.
We had a pretty cool meeting with a few seasoned specialists in the field (one of whose names I remember now) while in the early stages of testing, and the crude "printable circuits" people are talking about -- solar cells, hobbyist circuitry, etc -- are fairly paleolithic compared to what is expected. We're talking things like functioning "super-flat-screen" monitors printed on a plain piece of paper, to name one example I can't forget. Everything from product labels & boxes to newspapers and magazine to the walls of homes will be printed within invisible circuitry that will fluoresce or otherwise display an image just like a monitor. Printable solar cells will be the likely power source, but cells are just the crude beginnings of what is to come.
There is a dark side to this. Printable circuits can also be used much like the security devices in library books and DVD videos in stores. A scanner can read the circuit from a distance, making a person trackable and identifiable. A huge amount of information can be stored in the circuit. The repercussions to privacy can be staggering.
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In my company we use to print silver ink in silk screen process for years !
It's one of the most widespread technology to print antenna on plastic/paper for biometric chip inlays you would find in your passport.
Silver is used because aluminium and copper are not good enough conductors when spread in powder in a varnish base which is mandatory to be printable and flexible.
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I would like to be able to give it a try... It will be interesting to see what the overall system cost is to get this done. Will it really be available to DIYers?
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If the name is any indication they use nano sized silver particles in the ink. The health risks from nano-particles are not well known and the stuff is completely unregulated right now. There is evidence that nanoparticles penetrate skin and other membranes (such as the brain-blood barrier) in our body that normal materials we are exposed to does not.
There was some cleaning product with nano particles used as an aerosol in Germany some years ago. After reports of related dizziness and headache they where removed from market again.
I would be careful around this stuff (and anything that contains nano-particles). If you come in contact with it, treat it as toxic (ie don't inhale/ingest and don't get it on your skin)... in fact I don't even know if latex gloves would help, they might penetrate small pores in the gloves as well. :(
So until they have tested this stuff medically properly, and there is proper regulation, I would stay away.
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And before anyone points out that molecules are smaller: Yes they are, but we have been exposed to them for a long time and developed resistance and have regulations. Silver is toxic and nano sized silver particles might have ways of penetrate the body that is not known and normal silver would not. I don't want to be "alarmist", but being careful around this stuff might be motivated until we understand the effect it has on the body better. (Remember radioactive toothpaste and mineral water?)
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