We've spoken a lot about the 3D printing applications possible with the Discov3ry paste extruder but there are also some incredibly cool 2D projects that we want to draw some attention to as well. Printed electronics is one of these applications.
We got our hands on some Bare Conductive Electric Paint; a water-soluble, nontoxic and child-friendly material.
The electric paint has a surface resistivity of about 55 ohms/sq. in. at 50 micrometer layer thickness; these properties make it ideal for low-voltage, hobby style electronics.
In order to try out a real world application, our test pattern was a fractal antenna. Which, Wikipedia describes as
"an antenna that uses a fractal, self-similar design to maximize the length, or increase the perimeter (on inside sections or the outer structure), of material that can receive or transmit electromagnetic radiation within a given total surface area or volume."
Printing with the Electric Paint
Electric paint has a rather low viscosity. You can get a sense of the material by watching Charles scoop it into the syringe chamber.
After the paint is in, some effort was also needed to remove all of the air from the syringe. Basically, this means shaking and tapping the syringe a bunch of times.
When working with a new material, one of our first considerations is the size of the extruder tip.
The image below gives a sense of the different types of tips (the set on the left) and the different sizes of tips (the set on the right). The extruder tip sizes are available from 50 micrometers up to 1.5 mm internal diameter. For typical applications, you’d likely use a 300 micrometer or larger tip.
Given that electric paint has a rather low viscosity we chose to use a fairly small 150 micrometer extruder tip.
We tried printing with both tubular stainless steel, and conical plastic tips. We found that the electric paint and flowed more smoothly from the conical tips.
At this small scale, a bit of experimentation and practice was required to to optimize the printing for the right flow rate and print speed.
Substrates (Print Surface)
Since the Electric Paint is designed to work on a variety of surfaces we tested printing on glass, paper, and overhead transparency. The material held its shape well on each of the substrates, without running or smudging.
Here are some examples of our printed results.
On Overhead Transparency (internationally sourced coins for scale):
One important detail to keep in mind when working with smaller extrusion tip sizes is that bed leveling becomes more important.
In the case of the 150 micrometer tip, if the leveling is off by 150-200 micrometers, then there will be a gap between the tip and the substrate. When this occurred, the paint would bead at the tip instead of adhering to the substrate, resulting in a gap in the printed pattern.
In order to reduce the variation in bed height across the print surface, we scaled the original image down for testing on the glass and acrylic.
So... how’d it print?
The pattern printed beautifully once we got the bed leveled well.
For situations where you want to reliably reproduce a particular circuit, this would be much easier than making a stencil, or hand painting. Another advantage is the ability to rapidly iterate by making slight changes to your design files.
Our overall impression is that the Bare Conductive Electric Paint worked well with the Discov3ry extruder. It's a fantastic pairing for printing elaborate circuit patterns.
Rather than creating custom stencils for each of your circuit plans, you can digitally refine your designs, and easily replicate them using a printer if you want to avoid the labour of making custom stencils for each of your circuit plans.
Once the samples were dry, we cut out a portion of the bottom section of the antenna, which is how it's intended to funtion.
We did a few tests of the resistance across both the antenna, and the cut out section, just to see what we got.
The length, from tip to tip along the base of the antenna, was 7 cm. The resistance measured across the full antenna was 3.3 Ω.
he cut out section was 2.5 cm in length, and the resistance measured across it was 0.27 Ω.
Unfortunately, we didn’t get a chance to test the prints for their intended purpose as an HDTV antenna. Our intent was mainly to understand how to print with conductive ink.
We think this is a great project for those who are interested in both electronics and 3D printing. If you'd like to try it yourself, we have a few recommendations for best results:
The 150 micrometer conical tip was ideal for fine detail as long as the print bed was very level.
For larger resolution prints, the conical tips would still probably work best since they result in less flow resistance for the Electric Paint.
Alternately, though, the 1/4-inch length stainless steel tips are still very suitable.
Bare Conductive recommends printing just a thin layer for the increased flexibility, as thicker deposits can crack.
Bare also provides some great guidelines in their applications notes.
What else could you print with electric paint?
Here are some additional ideas:
Print Bare Conductive onto an iron-on transfer for printed wearable electronics.
Print your circuits in batches on label stickers, to easily stick it on to photos, greeting cards, business cards, etc.
Use the Discov3ry in a stand-alone mode (hold the tip in your hand like a pen), press ‘extrude’ in your printer software, then draw a circuit on something totally free-form, like a glove, laptop case, musical instrument...
We hope this experiment serves as a good proof of concept, and inspires you to try out other options for printing with electric paint.
If you’re excited about the possibilities for 3D printing with pastes, consider supporting our Kickstarter project to be one of the first people to experiment with a Discov3ry Paste Extruder.