Introduction: Conductive Materials
We have played around with different conductive materials to discover their properties and how it can be used.
Step 1: Conductive Paint
We tried out some conductive paint from bare conductive and a nickel conductive pen from circuit works. As a conductive material it can for example be used as wires, resistors, potentiometers and capacitive censors.
The paint/ink is easy to attach to different materials such as cardboard, paper, wood, wallpaper, walls, textiles, and some plastics. Be aware that the paint can crack or be scratched away, so very thin paths can easily be broken. It is also thick and sticky and can be differ cult to paint without stencils. But the stickiness also make it possible to use the paint as glue, which is a practical alternative to soldering if you don't need a very strong fastening. The paint can be mixed with water and is supposed to be suitable for screen printing & spray painting.
Since the paint is easy to apply on a lot of materials it can be used to hack everyday environment. Paint a circuit to get a signal if windows and doors in your house are locked.
Step 2: Conductive Thread
The conductive thread can be used in a lot of the same ways as the paint. It is not as conductive as traces printed on a circuit board, but has much more conductivity than the paint. This make it as great product to carry current for power and signals and can easily be sewn into fabrics. The thread we tested was a silver plated thread from spark fun that was thin enough to be sewn in a sewing machine (but it was easily tarnished)
We tried out different was of knitting the thread in hope to get a sensor that would be activated by stretching (and then higher resistance.) But the thread together with the wool didn't make an accurate output, and the thread was to conductive to get a variable output in our small tests.
We also used the thread to connect wires to conductive prints or sewn traces on fabrics. It worked best when we had several larger stitches to create a longer contact surface to the connecting flat.
The thread can for example be used in combination with buttons to create wearable, discrete switches.
Step 3: Conductive Stainless Fiber
This stainless fiber from spark fun is only 8 microns thick. It is soft and can be blended with other fibers and spun into thread or yarn, embedded into composite materials or even felted.
When we didn't blend the stainless fiber with other yarn, it was highly conductive and could work as a wire. We also tried to felt it and it did work fine as an soft on or of switch. We didn't manage to get an uniform material without proper felting equipment, so its not very accurate to behave as a sensor.
The fiber can be used to make soft, large switches inside toys, without loose parts. Or add some fibers in your children's pillow and you know when its not sleeping anymore.
Step 4: Conductive Fabric
This is a conductive knit fabric for use in e-textiles.It is silver-plated nylon that is stretchy in both directions.It is highly conductive with a surface resistivity of < 1 ohm/sq.
We tried to use the fabric to make a balloon sensor, but it didn't work that well when its evenly stretched. When we stretched a 20cm piece maximally the resistance was decresed by 1-1,5 Ohm (the same value for both directions, and 2,5 Ohm for the diagonal).
Since the difference of the resistance does´t change that much when stretched it can be differ cult to use it as a stretch sensor. Perhaps washing also will affect the conductivity over time so that it is differ cult to calculate accurate values.
The fabric has the ability to block electromagnetic radiation, witch is used by people that are afraid of radiation.
Step 5: Velostat
This conductive material from adafruit (also known as "Velostat" or "Linqstat") is pressure-sensitive: squeezing it will reduce the resistance. It is handy for making cheap, flexible pressure or bend sensors.
We tried to follow a bend sensor tutorial, but we struggled get it to work properly. There are a lot of tutorials showing great result, so we would like to try again to get it work.
With velostat you can even make a touchpad sensor that know where on the surface you push. (tutorial)
We also used Velostat to create an capacity sensor. Without being too accurate we managed to create a sound that would be brighter depending on your distance to the sheet or where on the sheet you touched it.
Velostat is also a part of The Sensor Film Kit which is a force-sensitive film that can be easily cut into any shape to be used as a sensor or switch for Arduino and other electronic projects. They have a instructables of how to make video controllers as well as parking sensors.
Step 6: ITO Plastic
We tested a sheet of ITO plastic from adafruit. ITO (Indium Tin Oxide) is a clear, highly conductive liquid/film. Our sheet was coated by ITO on a one side of a flexible plastic (PET) sheet. Be sure you test which side is the conductive one! It should also be possible to scratch away traces.
We tested to use it as a wire and it worked very well. It’s not possible to solder to this material, but you can use conductive inks, paints, copper tape (with conductive adhesive) and alligator clips to make contact.
The ITO plastic is used in touch screens, and give us a very nice opportunity to create invisible circuits.
Step 7: Conductive Tape
The conductive tape from adafruit can be used to bond two conductive surfaces together and allow a small (we'd say keep it under 100mA) current to flow through the tape.
The tape is only conductive across the thickness of the tape itself, not along the length or width. That means you you can tape onto fine, close individual circuits together without having to concern that you are connecting them together with the tape. This work because it is a regular adhesive tape with little chunks of conductive material every 0.1mm or so.
We found that the tape was not sticky/strong enough to connect LEDs or wires without having to push it, but it should work better for flat materials.
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