The glued circuit below has been hooked to a power supply and left on
for more than 3 weeks with no noticeable deterioration in performance.
There are many kinds of conductive epoxies, glues, and rubbers available. Unfortunately, they are for the most part quite expensive. So, for more than four years, I have been trying every possible combination of likely elements, compounds, and solvents that I could get my hands on, in order to make my own truly affordable conductive glue. Below is a picture of some of the many mixes I have tried. My original goal was to come up with a glue that was as useful as the nearest comparable commercial product. The conductive glue that I finally came up with is more flexible, less expensive, and has lower resistance than Wire Glue, the most affordable of the off the shelf conductive glues. For details on how to mix your own conductive glue and glue a circuit with it, you can check out the instructable I have posted at: Instructables: Make Conductive Glue and Glue a Circuit
Update on Conductive Glue Experiments
I have had mixed results in my experiments with powdered metals. While they often produce the lowest resistance per inch, they tend to make the resulting mix quite brittle. They also considerably increase the price of the glue mix. However, If you do your circuits on rigid materials they could be useful. Below are the results of my recent limited experiments with metals and Liquid Tape. They were measured using my standard of 1-1/2 metal to 1 Liquid Tape by volume. Tinned copper wires were placed about one inch apart and a conductive path about (when dry) 1/4 inch wide by 1/16 inch thick was produced.
Aluminum-Very high resistance
Antimony-Very high resistance
Tin-Very high resistance
Silicon metal-53 megohms
Iron- 79k ohms
Titanium- 7k ohms
Copper- 27 ohms, but easily cracks
Nickel- 5.8 ohms, the lowest resistance of anything I've tried, but I have yet to build a circuit with it. Some researchers have noted that while nickel has a low resistance in conductive glues, it has a tendency to oxidize and increase its resistance over time.
There are plenty of metals or other materials to try, if you are interested in doing your own experiments to come up with something better.
My original goal was to come up with a glue that was less expensive, had a lower resistance, and was more flexible than the nearest comparable commercial product. While there is room for improvement, I feel this glue is as useful as most of the off the shelf conductive glues. As for me, I am quite happy to continue experimenting with the proven graphite and liquid tape formula which has low cost, high flexibility, variable resistance, and many possibilities.
I also tried another Liquid Tape from the hardware store called "Gardner Bender Liquid Electrical tape" and It produced a resistance with graphite comparable to Wire Glue (90 ohms). Unfortunately, I only had the red version which may have increased the resistance. Similarly, I tried a white version of "North American Brush On Electrical Tape". Its resistance was 248 ohms. I suspect that the pigments that give the colors may add resistance to the resulting mix. This opens the possibility that the black versions may work better.
One side note, all these liquid tapes are great for insulating splices or exposed wires from shorts. They usually require two coats or more to get a good anti-corrosion seal, but I have found them easier to use and more compact than shrink tubing.
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