Paper Electronics: Conductive Paints, Inks, and More

This Instructable is all about the amazing technology of paper electronics and conductive materials. Instead of using stubborn wires and your rusty soldering skills to painstakingly connect components, why not use paint and glue? This tutorial will share various recipes to create your very own conductive paint, tape, glue, and ink. Using a maximum of 3 easy to find ingredients, these simple materials are easy to make. All of the conductive materials explained in this Instructable are based around the conductive paint (step 1). Using increments of different chemicals, the consistency of the paint can be changed from thick to thin (glue to ink). At the end of the Instructable a simple project will be shown using conductive materials (step 5). There is also a step that is dedicated interfacing conductive materials with kits and teaching classes and workshops.
Even though commercially available conductive materials work great, they are a wee pricey and often need to be ordered online. Another disadvantage of commercial products is that they are usually only available in conductive paint form.
To start off, I would like to share some of the science behind the main ingredient used in the conductive materials; graphite. Graphite is a mineral and a form of pure carbon. Graphite is very conductive and is sometimes used in arc-lamp electrodes. Because of its conductivity, graphite is the primary candidate for making conductive materials. Its other bonuses include being easy to obtain, mixing well with paint, and coming in a very fine powdered form.

Here are the supplies needed to make the conductive materials in this Instructable:

- powdered graphite lubricant- from from Ace Hardware or other hardware store
- black poster paint- from local craft store or from Amazon
- paint thinner- from local hardware store or from Amazon
- popsicle/mixing sticks- from local craft store or Walmart
- mixing cups- I used styrofoam cups from grocery store
- measuring spoon- baking spoons will work

To complete the ink and stamping steps and the project, you will need these additional supplies:
- light emitting diode (led) available at local Radioshack
- 3-volt coin cell battery- available at grocery store
- sponge- some type of sponge, I got mine out of an old printer ink cartridge
- airtight vial- any type of airtight container will work
- airtight plastic container- possibly tupperware or old food container
- paper

Now that the materials have been gathered, it is time to begin making conductive materials!

Warnings: Some of the projects and instructions in this Instructable use paint thinner. This chemical produces nasty fumes that probably aren't very healthy for you. Perform all projects using paint thinner in a well-ventilated room. I am not responsible for any accidents that may occur while using this Instructable.

This Instructable is submitted for Powell Cubs for the Instructables Sponsorship Program.

Step 1: Making Conductive Paint/ Base Material

     The first part of this tutorial features conductive paint. The paint will be the base of all of the other materials that are explained in this Instructable. The paint makes an ideal base because of its consistency. To make glue you add slightly more graphite powder, and to make ink a few drops of paint thinner is added... but onto that in later steps.
     Conductive paint sticks well to most materials, especially paper and cardboard. Anything that the poster paint will bond to, the conductive paint will as well. I have found that this mixture of conductive paint flexes well on paper. However, sharp creases and folds will lead to a crack, usually causing a shaky connection. The conductive paint will turn out to have the same flexibility as the paint that is mixed in. 
As a general rule of thumb, use this paint in low-medium areas of stress to ensure a reliable connection. For higher stress applications resort to one of the conductive inks mentioned later in the Instructable.
     The two materials used in conductive paint are powdered graphite and the poster paint. After much experimentation, I found that a mixture of 2 parts powdered graphite to 1 part black paint worked exceptionally well. 

Instructions: Using the measuring spoon, measure out two spoonfuls of powdered graphite and pour it into a mixing cup. Add 1 spoonful of the poster paint. Mix well, making sure all of the graphite is added. 

Application: Slather heavily onto the material (i.e- paper, cardboard) in the desired pattern using a paintbrush. Make sure that all lines are coated evenly. Allow a few hours to dry before using. Store remaining paint in an airtight container.

     When dry, the conductive paint has a very low amount of resistance. After several tests, I calculated the resistance to be around  
115 ohms per centimeter.  If the circuit schematic calls for a small resistor  (<115 ohms), it would be alright to omit it. I found that when you connect a new 9-volt battery to a painted line (of conductive paint) and attach a digital multimeter on the other side, the voltage detected is 9.27-9.28 volts out of 9.29-9.30 volts. In sum, there is a very minimal amount of voltage lost when using conductive paint. 

Step 2: Conductive Glue and Tape

     Now that the base paint has been concocted, other materials can be made. In this step I will highlight the making of conductive adhesives. Conductive tape and conductive glue will be shown.
Conductive Tape: Conductive tape can be used to bind paper and cardboard together, as well as connect components for a quick and easy prototype. I would not suggest using conductive tape for permanent or moving circuits, as it will become loose over time. 

Instructions: Paint a layer of conductive paint onto thin strips of paper. Wrap around the desired object tightly, ensuring a good connection. To store the tape, place the painted strips side by side in an air tight container or bag. 

Conductive Glue: Conductive glue can be made by adding more dry materials to the original base.  It could be used to create a binding substance for numerous sheets of paper, cardboard, etc. Glue can also be used to attach electronic components to the painted lines in a schematic. It bonds well to most materials, including the metal leads of components, paper products, and plastics. Since more graphite is added to the original base to make glue, the glue will have even less resistance, depending on the amount of graphite used.
Instructions: ​Mix up a batch of the base paint (2 parts graphite, 1 part black paint) in a mixing cup. Keep adding graphite powder, one part at a time, until the glue reaches the desired consistency. I found that 4 parts graphite to 1 part of paint was about the right consistency. Adjust the consistency to your desires.

Application: Using a paintbrush, slather the mixture on the component lead or desired surface. For thicker mixtures, use a mixing/popsicle stick to place a dollup of glue on the material. When gluing a component, ensure that the glue is contacting the lead of the component and the line of conductive paint. Allow a few hours for the paint to dry before using the circuit. Store in an airtight container.

Step 3: Conductive Ink

     Conductive ink is another necessity in the field of conductive materials. Ink's thin consistency makes it perfect to apply to paper and cardboard. My initial experiments in the conductive materials field were focused on conductive ink. I tried to mix water and graphite together. However, I soon found out that graphite and other conductive metals/minerals were not water soluble... the graphite would always settle to the bottom of the water, no matter how much mixing was done. Eventually, I gave up on ink and moved onto paints and glues.
     After succeeding at these, I came back to ink. My spark came when I was searching through the mess in our basement for more black paint. I saw a jug of paint thinner. Paint thinner is a solvent that is usually used to thin oil-based paints. It can be made of mineral spirits, acetone, naphtha or other nasty chemicals. To reiterate the warning in the intro, always use paint thinner in a well-ventilated area. 
     Conductive ink is much more flexible then conductive glue, and works better in high-stress applications. Conductive ink can be used in all sorts of applications.
     Once again, using the base paint described in step 1, paint thinner is mixed in. As might be expected, the paint thins into a ink-like consistency, depending on the amount of paint thinner used. After being made there are a number of ways that conductive ink can be applied. For a stamp/inkpad method refer to step 4.

Instructions: Mix up a batch of the base paint in a mixing cup. Add 1-2 parts of paint thinner to the mixture. Stir well with a popsicle stick. The substance will cling to the sides of the cup in long droplets. Just keep scraping the drops off the cup until well mixed. Add paint thinner until the concoction reaches the desired consistency. 

Application: Insert a paintbrush and scrape the cup. The ink will be sucked into the paintbrush and off of the cup. Apply the conductive ink to the desired surface or refer to step 4 for a tutorial on a conductive ink pad stamp. Store in an airtight container.

Step 4: Conductive Ink Stamps

     You know those cool stamps that you press onto a piece of paper to leave a meticulous ink pattern or lettering? Your teacher might have used one to stamp a "Good Job" on your worksheet when you were in school. Soon after creating the conductive ink, I realized that it should be applied in a different way then the paint. Instead of using a paintbrush, it would be fun to stamp circuitry onto a piece of paper. Using a stamp, you can neatly press a "printed" circuit board onto a piece of paper.
     In this part of the Instructable, I will demonstrate how to acquire your own stamp, and make a proper ink pad loaded with conductive ink.
     If you do not want to make your own stamp, you can customize and purchase professionally made rubber stamps from many online sites such as here.
Even though these stamps are pricey, if you are going to be making a lot of the same circuit board, these would come in very handy. Another idea for stamping is to use locally available stamps. You could stamp letters and use them as the wiring in your circuit. These stamps are available at your local craft store.

Instructions: 
The stamp: Since stamp-making is beyond this instructable, search the Internet for a tutorial on how to create your own stamp. A great collection of tutorials can be found here.
Create your stamp in the pattern of your desired schematic. For places where components connect, make circles for easy interfacing with conductive glue.

The ink pad: Insert the sponge in a air tight container with the lid removed. Mix up a batch of conductive ink as described in step 3. Try to make a ink of a very thin consistency, such as a consistency  nearly as thin as water. Mix it well and collect it in a brush. Paint the ink onto the sponge until it is soaking with conductive ink. If the ink is not absorbed, the ink is not thin enough.

Application: Press your stamp into the ink pad, ensuring equal coverage of ink. Push the stamp down onto the desired surface and pull up. If the desired area is not coated well, stamp again over the same spot. Repeat until the stamped area is all black and without visible paper. 

     Stamped circuits may be subject to a slightly higher resistance then normal brushed paint or ink because not as much ink is put down onto the surface. The resistance all depends on how much ink is put down during stamping and how wide the stamped lines are.

Step 5: Making a Simple Circuit

     Now that all the recipes for the conductive materials have been shown, it is time to use these in a circuit. During this step, I will demonstrate how to build a simple circuit using conductive paint, ink, glue, and conductive tape. The circuit consists of  an led and a  3 volt battery. A resistor is not needed in this circuit.  You will also need all of the previously mentioned conductive materials and a piece of paper.
Instructions: First, paint or stamp two parallel lines about 1/2 inch apart on a piece of paper. Attach a 1 inch piece of conductive tape to both sides of the 3 volt coin cell battery. Center the battery on its edge and press the tape onto the corresponding lines. Make sure that the tape and paint are making good contact. Next, use conductive glue to attach one of the led's leads to the other end of one of the painted lines, noting proper polarity. Remember that the flattened side of the led is the negative lead.  Bend the opposite lead of the led so that it is not touching the parallel line. Allow the circuit to dry. Finally, to turn on the circuit, press the bent lead down onto the painted line. This will close the circuit, and the led should turn on. 

Step 6: Kits!

     During this Instructable you have learned how to make conductive paint, tape, glue, ink, and stamps. You are probably wondering how else you could use your new knowledge. Conductive materials are a great way to make kits. Whether you are teaching a large group about electronics or just a few people, pre-made kits are an essential teaching tool for a hands-on experience. Conductive materials supply many advantages for making kits. 
     First of all, conductive materials are perfect for kids/adults who are new to electronics. When teaching an electronics class, it would be much easier if the kits did not require soldering and jumbles of confusing wires. Instead of messy and often irreversible solder, conductive glue would solve the problem with a fun and easy way to attach components. Conductive painted wires would provide an easy layout of the circuit. Students could easily be able to see what connected to what.
     Another pro of using conductive materials in kits is circuit boards. Instead of spending long hours and tons of money creating traditional circuit boards for the class, paper circuit boards could be mass produced using the stamping method. Identical boards could be created in an efficient manner. 
     Overall, paper electronics would make the perfect materials for kits. Teaching classes would be made easy, and budding electronic geniuses would have the opportunity to experiment with the cutting edge technology of conductive materials.

Here are a few things that could be included with kits:
- paper
- conductive paint, ink, tape, glue
- stamps/ or materials for a diy stamp
- paintbrush
- electronic components

Step 7: Conclusion/Other Ideas

     During this Instructable you first learned how to make conductive paint. Then, from there, the tutorial went on to explain the process of making conductive tape, glue and ink/stamps. With these conductive materials you now have the ability to make your circuits cheaper, thinner, easier, and more flexible. Hopefully you will be able to apply these materials to your future projects and experiments. As an ending note, I would like to share some of my ideas for more things that could be done with conductive materials. Since it is a fairly new technology, there are loads of things that could be developed. Here are a few:
- a conductive ink printer
- colored conductive materials
- paper components, electronic components that could be stamped onto paper
- interactive paper business cards or newspaper
- transparent or translucent conductive materials
     Thank you for reading this Instructable. I hope that you have learned a ton about conductive materials and their applications. Thank you

-icecats-