Wednesday, October 25, 2006


Metallic Clay

Another interesting material: Metallic clay is modeling clay consisting of mostly silver particles. It can be molded like ordinary clay but, when fired, becomes nearly pure silver. The resulting piece is almost certainly conductive. Completely impractical for Reprap machines but an interesting concept.

Makes me wonder if we could come up with a 'conductive plastic' in a similar method...

Could you saturate a plastic with enough (non-melted) metal partciles that the resulting 'compound' would be conductive?

Someone had mentioned something similar in regards to disolving a powdered metal into a metal with a lower melting point and I'm wondering how that would translate to suspending in plastic...

A couple of 'side ideas' that come to mind...

If we can get current, but get resistance based on the amount of metal in it (as opposed to works vs not works), we could prototype crude resistors.

If 'disolving' the metal into the plastic doesn't work, what about simple 'pouring'/depositing the powdered/chipped metal particles into a 'pathway' and extruding plastic over them. I'm thinking that (at least with chips/fragments instead of just dust) we could get a pathway 'thin' enough that enough of the metal would be 'stuck to plastic' that it would hold itself together without 'pouring out' (similarly, the entire circuit would be 'sealed' in the plastic).
The fab@home group use a silver colliod of that nature to deposit conductors for batteries and could presumably use it for other purposes. I haven't been able to locate any reference to it's exact formula but they extrude it from a syringe, so presumably finely ground silver in a plasic with an evaporating solvent/carrier fluid. Link:
***Makes me wonder if we could come up with a 'conductive plastic' in a similar method...***

You can buy it off-the-shelf.;jsessionid=ac112b6b1f43985094d943b047388023e43e92be0337.e3eTa3aSaxmTe3uQb38Mb30Rci1ynknvrkLOlQzNp65In0?sc=2&category=174

I've got some. :-)

Your session didn't save very well, so I'm not exactly sure what you're looking at, but everything i saw on there looked quite expensive... I don't think we need to go with a semi-precious(?) metal like silver...
Be careful that you don't make a mess of your economics. A little of that silver/polymer mix can go a long way. Remember that you are only making conductive traces, not parts, with this stuff. :-)
***Be careful that you don't make a mess of your economics.***

I'm trying not to... Couple things I'm taking into consideration:

#1> That doesn't look to be very recycle friendly...
#2> At this stage with the reprap, I don't see reliable precision that would allow for 'small compact' circuits, so I expect lots of big, thick circuits to ensure the job gets done right...
#3> At this stage with the reprap, and with anything made by it for the forseeable future, the circuit boards have changed at least twice since I started making mine, so I see myself, and other 'early adopters' remaking the 'same circuitry' a number of times as it evolves and developes...
#4> In the wilds of africa, and other 2nd/3rd world countries (heck, even 2nd/3rd world cities!), I could easily see you getting mugged/etc for a 2oz bottle of 'liquid silver', but some ground-up 'metal' suspended in 'plastic' isn't going to get the same consideration...

I've also got crazy visions of actually making some components with the reprap, and I'm guessing that making something like a resistor would be a lot easier with some sort of metal suspended in plastic mix than this sort of 'liquid metal'... If you can vary the resistance of the 'conductive plastic' by adjusting the 'size' of it and by the metal amount/type, you could build the resistors into the pathways themselves... (why add resistors to your circuitry when you can lay pathways with the right resistances to move the current how it needs to be moved? I feel, with a properly evolved RepRap, we can do away with component/chip based circuitry, and simply create circuitry that is its own components...)

At least at this point, I'm looking at everything the reprap produces as 'disposable' 'single use' items... Two of my hobbies are RC and Rocketry... both of which tend to suffer a fair amount of damage through the course of normal operations... If i build some circuitry for my rocket, and it nose dives, and (probably) breaks that circuitry, I'll just melt it down and remake it... Any components I can salvage I'll reuse, the rest I'll replace... If I'm using liquid metal, that's lost to me... and I've probably got to scrape it off or something to get rid of it... If I'm using 'conductive plastic', I can, with some effort and quality control, recycle that board or those pathways and reuse them... (I'd probably save up a dozen or so of the small circuit boards and recycle them all at once...) The 'conductive plastic' wouldn't be exactly like it was before, but you could just add more plastic or metal to adjust/fix the resistance (i'm hopeing)...

This could all... not work... but if it does, I see it being a lot more useful than 'liquid metal'...
By liquid metal, I'm guessing that you are talking about things like Field's metal eutectics?
I'm pretty sure he's talking about the variants on conductive ink / metal clay / etc as 'liquid metal' - field's metal or solder feel reasonably recyclable, if they can be gotten out, which should be doable with varying melt points and a pulverization rig.
I thought I posted this answer earlier! anyhow, no, I was talking about the 'circuit writer' on that site you had posted... isn't that what you were talking about?

CircuitWriterTM, #CW100L-4

CircuitWriterTM Liquid, 100%, silver-based, 125 grams, coated bottle (Includes $20.00 surcharge for silver pricing)
Part No. CW100L-4
Price: $89.95

I'm not entirley familiar with Fields metal, but it's my understanding that it's just a realy low temperature metal? (partialy because of things like lead?) Temperature based stuff is fine, I'm just looking for something with a little more flexibility than 'non reistant pathways' is all...

The recycling issue I have with the 'circuit writer' is that it's solvent based, not temperature... From what I can tell, it's just acryllic paint with silver in it... my gf's got that in iron (for a crafting 'rust' effect on any surface) at 1/20th the cost...
***The recycling issue I have with the 'circuit writer' is that it's solvent based, not temperature... From what I can tell, it's just acryllic paint with silver in it... my gf's got that in iron (for a crafting 'rust' effect on any surface) at 1/20th the cost...***

It's acrylic plastic dissolved in acetone in solution with silver dust. I actually got the pen, which is quite handy.

I guess I should have said more. There is nothing stopping someone from mixing silver dust in polymer powder such as CAPA and making filament out of it. It would work just as well. That was what I was suggesting. I see that I didn't fully explain what I meant, now. :-(
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