Editing Conductive Paint Lessons

=Lessons on Conductive Paint=

Related to Pulse Choker Hack Notes for July 15th, 2009:

"We tried silk screening silver conductive paint (MG Chemicals 842-20G) onto two different types of fabric, a water resistant one and a water proof "leather like" one.  Both showed very high resistance (higher than the meter can read) even for very short thick traces.  It looks really cool though - hopefully we can figure out what we're doing wrong, and make this work.  We also tried measuring the resistance of a huge dollop of paint on the spoon: silver = infinite resistance (!), copper = 200kOhms. It didn't matter if the paint was dried or wet. Note that we shook the bottle prior to use to ensure that the silver particles were dispersed evenly."

==Types of Conductive Paint==

* Opaque paint
** Nickel (Ni): 
***   Higher resistance - ~5-6 ohms per square
***   Cracks when dried and flexed - [http://someoneknows.wordpress.com/2008/12/06/desktop-fabrication-wearable-electronics-circuitry/ Desktop Fabrication: Wearable Electronics Circuitry]

** Copper (Cu):
***    Higher resistance - ~5 ohms per square.
***    Reasonably priced - ~$30 for 4 oz
***    We bought CuPro-Cote #292-4 from [http://www.lessemf.com/paint.html Less EMF Inc.], which wasn't viscous, not even quite as viscous as tempera paint. It also forms subtle flakes and could potentially crack like the Ni paint.

** Silver (Ag): 
***    Low resistance - ~0.1 ohms per square according to [http://someoneknows.wordpress.com/2008/12/06/desktop-fabrication-wearable-electronics-circuitry/ Desktop Fabrication: Wearable Electronics Circuitry]. The type we bought ([http://www.mgchemicals.com/products/842.html MG Chemicals 842-20G)] promises 0.2 ohms/mil (or ~7.9 ohms/mm)
***    Expensive - ~$30 for 0.7 oz (20 g) from [http://www.lessemf.com/paint.html Less EMF Inc.]


* Transparent paint
** [http://www.agfa.com/en/sp/solutions/orgacon_electronic_materials/index.jsp Orgacon] from Agfa - conductive, can be flexed, transparent, can be silk-screened
   

* Alternatives
** Wire glue - $4 for 0.3 oz
** Conductive pen

==Heeds==

* Shake paint well to ensure metal particles are well dispersed. Better yet, stir it a lot!
* Keep ink wet while working with it. If work time is protracted, mix paint frequently
* Resistivity measures are suppose to be accurate only when paint has fully dried
* Some paints are more dilute than others. One guy used silver paint, which bled beyond his mask ([http://accelenation.com/?ac.id.121.1 accelenation.com]).

==Uses==

* Auto repair
** It may be cheaper to purchase conductive paint as the rear window defogger paint at the auto store. I haven't done so. Most defoggers use copper paint.

* Microscopy, i.e. scanning electron microscopy (SEM)
** Companies specializing in SEM equipment note that some paints particularly plantinum may need to be placed in an ultrasonic bath for a few minutes ([http://www.2spi.com/catalog/spec_prep/platinum-paint.shtml SPI Supplies])
** Microscopy often utilizes different concentrations of metal particles in conductive paint, so these websites can provide you with a gradient of resistivity in their inventory of paints. M.E. Taylor's [http://www.semicro.org/ SEMicro] division has three concentrations of silver paint: 18%, 36%, and 50% Ag.

* Art
** Paper Circuits by Leah Buckley: conductive paint, magnetic paint, magnets
** Paper printed circuit board by Peter Blasser