Step 6: Make Conductive Fabric, Conductive Thread, and Conductive tape
You can make various fabrics conductive by coating them with the spatula method. Simply take conductive glue mix #4 and spread it thin and even on the surface using a plastic credit card or metal spatula (pic 17). Pic 18 shows the resulting coated fabric that can then be cut to size. For minimum resistance it usually takes a second coat after the first has dried. The resistance is usually around 300 to 1,000 ohms per inch. This is too high for most low power transmission, but can be useful for sending signals across flexible joints or for making switches and sensors. It may also have high voltage possibilities. I have not had time to try it, but it may be possible to plate this kind of conductive fabric with copper or nickel and decrease the resistance dramatically. Pic 16 shows the flexibility of the resulting conductive fabric.
Make an Almost Transparent Conductive Fabric
I have successfully coated nylon, cotton jean material, neoprene and polyester. Using the method above, you can even coat nylon or polyester netting fabric which results in an almost transparent fabric. See pic14. Pic 15 shows the 20 squares per inch fabric under a 50x magnification. You can see that the resulting conductive coating is quite thin.
If you are interested in buying metal plated conductive fabrics that are somewhat expensive but have very low conductivity, (.1 ohm to 5 ohms per inch) you should check out: http://www.lessemf.com They have a great selection of conductive fabrics.
Make Conductive Thread
By running thread through glue mix #1 or #4 and holding it down in the mix with a notched Popsicle stick, you can make most threads conductive. See pic 19. To make sure they dry straight, you should hang them with one end weighted until they are dry. I have successfully coated nylon fishing line, cotton thread, Dacron thread, and cotton yarn. Generally, the larger the diameter of the thread, the less the final resistance. With two coats, the resistance is around 700 ohms to 2k ohms per inch.
With this kind of resistance, this do it yourself conductive thread is not going to replace the commercial conductive thread, the best of which has a resistance of around 2 ohms per inch and is more flexible and easier to sew. It is however, useful for transferring signals and creating thin low power resistors. It may also be useful for some high voltage applications. It might be possible to plate this kind of conductive thread with copper or nickel and significantly decrease the resistance.
Conductive Thread at Wal-Mart
Wal-Mart sells a thread in their fabric department that is conductive. It is called: Coates Metallic Decorative Thread. It comes in a silver or gold color but I have had the best luck with the silver thread. It is unfortunately coated with a very thin clear polymer that insulates the spiral wound thin metal inside and probably keeps it from oxidizing. This prevents you from simply hooking up a test meter to measure resistance.
I have tried scraping the surface and I have tried various solvents to try and melt off the coating without much success. You can, however, use conductive glue mix #1 to glue wires or regular conductive thread to the ends of a length of the Coats thread. The glue joints will add resistance, but they make this very thin thread (it is thinner than the commercial conductive thread) usable for conducting signals. Since they are insulated with a plastic coating they can be bundled together without shorting and run like wires. The resistance varies depending on the quality of the glue joint, but it usually results in a resistance of about 80 to 200 ohms per inch for a one foot length of thread.
Make Conductive Duct Tape
You can make the back of most tapes, including duct tape, conductive by coating one or two coats of mix #4 on the back side of the tape. If you want to use the tape for electromagnetic shielding, you can also coat the adhesive side with mix #4 and then wrap the tape around whatever it is shielding before the glue dries. A bit messy, but it works. For duct tape, the resistance is about 200 to 300 ohms per linear inch.
Make Conductive Aluminum Tape
You can make a more conductive tape using regular aluminum foil (see pic 20). For instance, if you want to transmit low power DC across a wall, you can cut the foil about 1/2" wide and glue it flat with Dap contact cement or Goop. Where you need to glue two strips together for longer runs or to turn corners, you can use conductive glue mix #1. While 1/2" wide aluminum foil has a resistance of about .1 ohms per foot, glued splices 1" long and 1/2" wide tend to have a resistance of 3-4 ohms. You can then use the same mix to glue on LEDs or other components to the foil. If you paint over with a good latex paint, you can make most of the circuit almost invisible.
Another way that works well and is less messy, is to coat the duct tape or aluminum foil with conductive glue #4 and wait until it is fairly dry but still sticky and then press it onto a surface. If you put on the right thickness of glue this can eliminate the ooze out and it will work similar to regular tape.