Conductive Paint Lessons

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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 - 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 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 Desktop Fabrication: Wearable Electronics Circuitry. The type we bought (MG Chemicals 842-20G) promises 0.2 ohms/mil (or ~7.9 ohms/mm)
    • Expensive - ~$30 for 0.7 oz (20 g) from Less EMF Inc.

• Transparent paint
  • 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 (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 (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 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