Make Conductive Rubber: Transparent Stylus-iPod/iPhone

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About: I believe that the purpose of life is to learn how to do our best and not give in to the weaker way.

Intro: Make Conductive Rubber: Transparent Stylus-iPod/iPhone


I call it Oogoo II. It is a DIY conductive silicone rubber that can be used to create a transparent stylus for iPod, iPhone, iPad, and other capacitive screen smart phones. Because the contact part of the stylus is transparent, you can see your lines and draw more precisely than with a regular stylus.


This instructable shows how to make conductive rubber and use it to create three types of stylus:

1 Hack any pen or pencil and turn it into a standard type stylus for pressing keys or drawing sketches while still allowing it to write on paper.

2 Use conductive rubber as a flexible glue to make a transparent flexible round tip stylus for precision use in drawing and key pressing.

3 Use conductive rubber to make a flat transparent paint brush tip stylus for use in drawing and paint programs. It fits in a wallet

The intro pic shows the paint brush style drawing a line on an iPod.

Step 1: Materials

The step 1 pic shows the different types of stylus that can be made using conductive rubber.
The thumb pic shows most of the main materials used


Materials

Paraffin or candle wax

Naphtha solvent from hardware store

Silicone Caulk from hardware store

Corn starch from grocery store

Carbon Graphite powder- Available in larger quantities from: http://www.elementalscientific.net/
Available in smaller quantities at your local hardware store. It's called lubricating graphite and comes in small tubes or bottles.

VeilSheild conductive fabric from: http://www.lessemf.com/fabric.html
Also shown is a nickel plated fabric that is no longer available.

Mixing cup

Popsicle stick

Pen or Pencil

Small diameter brass or metal tubing or rod from: http://www.micromark.com/

Step 2: How It Works

Oogoo II-A Conductive Rubber
You can make your own conductive rubber from silicone caulk, corn starch and graphite powder. This creates a silicone rubber which can be made thin enough to paint on or thick enough to cast into molds. While it is not as conductive as wire or conductive thread, it is more than conductive enough to make a variety of capacitive stylus.

Capacitive Stylus
The standard stylus for a capacitive screen uses conductive rubber or conductive foam to replace your finger on the screen. Every persons body has a small capacitance. When you touch a capacitive sensitive screen, you change the capacitance where you touch. Such screens are designed to detect changes in capacitance and locate exactly where they are on the screen. When you hold and touch a conductive stylus to a screen your capacitance is transferred to the screen and detected by its sensors.

Transparent Stylus Tip
Two of the stylus made in this instructable use VeilSheild conductive fabric as the stylus tip. Because this fabric is 70% transparent it allows you to see exactly where you are touching the screen. The conductive fabric is glued to a conductive metal handle which transfers the bodies capacitance to the screen.

Step 3: Making Conductive Rubber

Mixing Oogoo II
Oogoo II is basically Oogoo with the addition of graphite to make it conductive and a solvent (Naphtha) to make it possible to mix.

Add three parts graphite powder (by volume) to 1/4 part corn starch to one part silicone caulk. A typical first mix would be 3/4 teaspoon of graphite to 1/16 teaspoon corn starch to 1/4 teaspoon silicone caulk.

First mix the graphite and corn starch together with enough Naphtha to make a thick paste of the powders. Then add the silicone caulk and mix it very well with a Popsicle stick or stirring rod. You want to end up with a mix about the consistency of smooth peanut butter.

WARNING: Naphtha is a sickly-sweet smelling solvent that wants to dissolve your brain cells if you breathe too much of it. Make the mix outside with good ventilation or inside under a vent hood. Wear safety glasses and nitrile gloves, as it can be absorbed by the skin.

I tried at least a dozen different solvents. While other solvents can be used instead of Naphtha, it has the advantage that it evaporates extremely fast and most of the odor is gone in a few hours. Other solvents can take a day or two to dissipate and increase the set up time.

Mix in small batches and use it quickly before it starts to skin up. It will typically set up enough in two or three hours to de-mold. Let it completely set up overnight before using it.

Other Mixes
At about two parts graphite to one silicone caulk, the mix starts to become usefully conductive. Adding more than 3 parts graphite will reduce the flexibility of the final rubber.

Step 4: Turn a Pencil or Pen Into a Stylus

Any pen or pencil can be made into a stylus while still maintaining the ability to write on paper.

Make A Stylus Tip Mold
A quick mold can be made by drilling a 3/8" hole in a block of paraffin or candle wax. Drill it 1/2" to 5/8" deep.

Cast With Oogoo II
1-Set up a clamp with a spacer to hold a pencil or pen 1/8" to 3/16" from the bottom of the hole and then remove the assembly from the hole.

2-Fill the hole flush with with a mix of Oogoo II.

3-Reinsert the pen or pencil and center in the hole. See thumb pic 1. With a toothpick smooth any Oogoo II that oozes out onto the body of the writing instrument.

4-After two or three hours remove it from the mold.

5-The diameter of the cast rubber tip will be larger than most pens and pencils. Mix up another batch and smooth it around the tip to taper it to the body of the pencil or pen. This will give you a conductive area to grip. You can coat the conductive rubber as far up the pen or pencil to where you are likely to hold it.

6-Let it dry overnight before you try to use it. A standard drill bit will leave a pointy tip. Sand it down lightly to make the tip more rounded.

Second thumb pic shows the finished pencil.
Third thumb pic shows a pen done in the same manner.

Step 5: Make a Transparent Round Tip Stylus

This style of stylus allows you to see with more precision exactly where you are drawing a line or pushing a button.

1-Cut a 1/8" diameter metal tube or rod about 4" long to make a handle.

2-Cut a piece of VeilSheild conductive fabric into a 3/8" to 1/2" diameter circle.

3-Set up a clamp to hold the handle about 1/8 off the conductive fabric at a slight angle.

4-Mix up some conductive rubber and put enough on the handle end to glue it to the center of the fabric while held in the clamp. See first thumb pic.

5-Let it set up for three or four hours and it is ready to use. The second thumb pic shows the finished stylus.

If you center the handle end on the fabric it will usually draw under the handle end. If you glue it off center, you can see the line as it is drawn.

Step 6: Make a Transparent Paint Brush Stylus

This stylus is flat and thin enough to put in a wallet. It draws and paints very much like a paint brush. It is pulled in the same direction you would pull a brush.

1-Cut a piece of 1/32" double sided copper clad circuit board to make the handle. Cut it 3 or 4 inches long and about 3/8" wide.

2-Cut a piece of VeilSheild conductive fabric about 7/8" long by 5/8" wide. Cut it in the angular shape shown.

3.Mix a very small amount of Oogoo II and use it to glue the conductive fabric to the end of the handle. The stylus is used glue side down so the bulge of the conductive rubber keeps the circuit board from scratching your screen.

The second thumb pic shows the glue joint.
The third thumb pic shows the top of the stylus

Step 7: Other Possibilites

The step 7 pic shows how Oogoo II can be formed into thicker objects or rolled into thin sheets. It also sticks well to regular non- conducting Oogoo (the blue part of the pyramid).

Other Kinds Of stylus
There are many other kinds of shapes or forms that can be made into a capacitive stylus. An Oogoo II tipped ring might be worth a try. Other shapes of conductive fabric might produce interesting results.

Robot Skin
As the step 7 pic shows, you can form thin skins of conductive rubber that could be used to create pressure sensitive robot skin.

Shielding
This kind of conductive rubber sticks well to almost anything. It also shrinks as it sets up. So if you use it to coat wires or enclosures it will shrink wrap the object. Embed an exposed wire that goes to ground and it can be used as electrical shielding.

Conductive Glue
Oogoo II works quite well as a conductive glue. A mix of 4 or 5 graphite to 1 silicone caulk has fairly low resistance and can be used to glue wires, conductive fabric, conductive thread and electronic components together into circuits.


For other ways of making conductive glue see here: https://www.instructables.com/id/Make-Conductive-Glue-and-Glue-a-Circuit/

For other uses of conductive glue see here: https://www.instructables.com/id/Conductive-Glue-And-Conductive-Thread-Make-an-LED

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32 Discussions

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MaxT77

Question 4 weeks ago

Will this work for active styluses? I ran out of 2.3mm nibs and can't find places where they sell it, even online (online stores in PH)

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Orngrimm

6 years ago on Introduction

I wanted to try this instr. but wasnt able to get hold of naphta... It is called Napthalene and was used in Moth-balls, but got ditched because of health-problems...

And nobody i asked knew a way to thin the silicone...

So i then headed back home (Quite depressed to be honest) and tryed some solvents i had at hand. White spirit, petrol, universal-laquer-thinner, ...
All gave a major mess and didnt really thin out the silicone.

I found on the nets, that some solvents are also able to thin silicone:
toluol and xylol, but both are de facto banned due to health-concerns.
An alternative is cyclohexan (German name, dont know eng), but it is hard to get hold of it.
Then i found some guys who make roll-on-silicone for theyr projets and the use turpentine or Mineral turpentine to thin the silicone to a thin paste to roll-on.
Will try this in the evening, since turpentine is quite cheap and freely available. Will report back.

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TheoD25Orngrimm

Reply 6 months ago

Naphtha is a Zippo lighter fluid sold on every cornershop

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PhelineOrngrimm

Reply 1 year ago

It sounds like you're not in the US. I can head over to my fantastic locally owned hardware store and buy xylol and naphtha (as well as other solvents). Some Home Depot stores try harder/have more autonomy and may have a decent selection. (Never suggest economy killer walmart). I notice a lot of solvents are associated with, but not exclusive to particular technologies or materials like fiberglass. Maybe you can find specialty suppliers for some of the solvents you can't find locally to you.

Turpentine sounds horrible as a substitute since it's slow drying. How about acetone?

I'm happy I found this to experiment with pens and other things I already have. Thanks.

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OrngrimmPheline

Reply 1 year ago

Welcome from the past! :)
Acetone didnt really mix well... It stayed clumpy as the other solvents i mentioned. Turpentine was much better.
And the slow-dry was no problem. Makes it much easyer to work with to be honest...

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switch62Orngrimm

Reply 6 years ago on Introduction

Just to clear up some confusion. Naphtha and Naphthalene are not necessarily the same thing.

Naphthalene was used in moth balls and is solid at room temperature.  It is obtained primarily from coal tar.

Naphtha liquid is a mixture of hydrocarbons obtained from oil distillation.  It is used for camp stoves, lanterns, lighters, and as a general solvent.  It is also known as Shellite or Recosol R55 in Australia.  Wikipedia has some links to manufacturers MSDS sheets.  You could try camping supply shops for the stove fuel (though some stoves use Kerosene or Methylated Spirits). 

Unfortunately very few, if any, solvents are competely safe.

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OrngrimmOrngrimm

Reply 6 years ago on Introduction

Aye. Turpentine works great for thinning silicone.
It started clumpy like the other solvents, but got smoother really fast.

Here is a trick on how to mix it best:
1.: Measure your amount of turpentine to your mixing-cup
2.: squeeze the silicone directly in the turpentine
3.: Mix well till no clumps are left. Easy to see now since it is still a clear paste.
4.: Add your carbon to it and mix well.

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JeriA2

Question 8 months ago on Step 4

I do not understand about the drill bit. I can't find a drill bit in any of the pictures. BUT, I love your work. Thumbs UP!

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tryb01

1 year ago

I tried this recipe & had some success but wasn't completely happy with it because the high concentrations of graphite needed made it feel slick/oily & left smudges on things. It wasn't very durable & would break easily if laterally stressed. Lower graphite concentrations meant poor conductivity. It would work one one part & not on another part of the tip. I decided to try substituting super fine steel particles in place of the graphite. Using 0000 steel wool & scissors I made a small amount of steel powder to mix in. This worked much better. The extremely tiny steel fibers are randomly intermixed with the silicon with very few sitting right on the surface so did not scratch the screen at all. Of course, if you concentrate a lot of steel fiber in the exposed part of the tip & scrub it hard against the screen you may scratch it. This substitution gave better conductivity all over the tip, no smudges, & much more resistant to breaking/tearing under stress. I work with disabled people some of whom use their stylus to perform many tasks besides touch screen access . They need a durable tip & don't want smudges on everything it touches. Copper or other conductive metal dust could also work but may react to the other chemicals in the silicon caulk.

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Kryptaos

1 year ago

I'm making a Predator cosplay and I want to use this stuff to make the claw tips essentially styluses so that I can use my phone normally while in costume... This looks really neat and I'm looking forward to trying it out.

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SammyM12

2 years ago

Hello, do you have any measurements about the resistivity of the conductive rubber? Thank you!

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ahg14

3 years ago on Introduction

I am needing help making a stylus for my child with disabilities. She only has control of her head. She wants to join the school band and use her iPod Touch as her instrument. We have an app that is a drum head and she wants to have a stylus attached near her head so that she can hit her iPod and make a drum sound. Can I make a sheet of Oogoo II and wrap it around something (what should that be made of?) that I can mount on her wheelchair near her head? Her iPod will be mounted as well. This is all way out of my comfort zone and I would appreciate any help you can lend! Thanks, in advance, for your time! (I have been in touch with ShapeDad on Etzy, but thought I would ask for your advice as well).

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mikey77ahg14

Reply 3 years ago on Introduction

One thing you could try would be to glue a stylus to bottom of the bill of a baseball cap. You could glue a pencil to the bill using hot glue or silicone with the eraser end away from the cap. You could then coat the eraser with Oogoo II with a bare copper wire embedded in it. The wire would run back to just before the sweat band under the bill.

Embed the other end of the wire in more Oogoo II that will roll around ( a thin coat) onto the sweat band. This will make electrical contact with the forehead.

Put the Oogoo II on thin and be sure and let it cure a day or more until the vinegar smell is gone. Wash the part that is in contact with the forehead with warm soapy water before using.

If the pencil comes out looking funky, you can wrap it with cloth or paper to tidy it up as long as the coated eraser that contacts the ipod is left exposed.

Hope that helps.

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I am very impressed by this I made a 3d printed stylus base and am posting a link to your page on all my 3d downloads sites this project of yours finishes mine thanks for posting it found it in google search. here's one of my places I posted it. i put it here for you to see what can be done if you colaberate :) I hope you like it.

https://www.instructables.com/id/printable-stylus-base-with-link-to-make-the-rubber/

printble_stylus_base.png
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Joe Byers

5 years ago on Step 3

Do you know if pencil lead graphite will work?

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The Daeng

5 years ago on Introduction

can i replace silicone glue with another type glue with rubber base?

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Creaturiste

6 years ago on Introduction

Because the solvent odor of Paint thinner takes a LONG time to off-gaz, I decided to not use any on my last batch of molds made with Oogoo.
I was just careful at the application, with my fingers for the detail coat, and then with a small painting knife for the thickness.

One trick is to use a mold to make sure most surfaces are the shape we want, and for whatever lumpy surface remaining, a bit of rubbing alcohol on your gloved finger can smooth it out rather nicely.

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foobear

6 years ago on Introduction

I wish there was a way to make a fine point conductive stylus that could be used like a fine point pen. There seems to be no way to have anything but a klunky round edged thing. Though your transparent stylus seems at least a bit closer.