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/

Comments

[JesusGeek]

Just put aluminum on the end of a pencil or piece of cardboard, and wrap wire all around it.

[The Daeng]

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

[Creaturiste]

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.

[foobear]

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.

[Orngrimm]

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.

[switch62]

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.

[Orngrimm]

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.

[sciman1]

did you just...
your talking to yourself...

[andreschouhy]

Can I use kerosene instead of naphtha?

[andreschouhy]

Not. Just tried it. Didn't work at all... no conductivity. Maybe I'm mixing wrong proportions.

[jcurme]

Will adding graphite powder to PlastiDip make a material that is conductive enough to use for an iPhone stylus?

[roliop]

Could you tell us what other solvents you tried ?
Might save me buying yet another noxious concoction and it would be interesting to compare the different ones.
Thanks,
rp

[mikey77]

You can use mineral spirits, acetone, xylene, or toluene but they all have nasty fumes and take several days to dissipate in thicker casting. The Naphtha has the advantage that it evaporates fast and loses most of its smell overnight.

Solvents that give off less noxious fumes and can be used to thin Oogoo and Oogoo II are turpentine and Citrus Solvent. Their only problem is that they can take several days to evaporate in a thicker cast of silicone rubber. For paint thicknesses they work fine but set up pretty slow.

[Morgantao]

I thought Graphite was a poor conductor. I remember using a pencil as a dimmer (variable resistor) as a kid... Is it really good enough for making circuits?
Also, where I live it seems pretty much impossible to get graphite (other than crushing pencils that is). Is there an alternative to using Graphite?
I'm guessing you need a fine powder, so that counts powdered copper...

[Orngrimm]

You dont need to conduct huge ammounts of power.
Graphite IS a poor conductor, but it is more than good enough to transfer a charge.
A charge is only a tinytiny ammount of electrons...

See it from the other side:
Your skin is an even more worse of a conductor than the conductive rubber and yet the smartphones are able to pick up your charge-differential... :)

Copper whould work, but remember: It is the same as with glass: If you grind your shards, shards still remain shards with sharp edges.
Same goes for normal copper-powder. If they have some shard edges, you will ruin your display quite fast!

Thats the nice thin with graphite!
It is soft --> Edges get polished down in seconds (on a micro-scale that is... more is not necessary)

[blorgggg]

This looks awesome! can't wait to try it out!

[TabbyDeAnne]

Wow! Thanks! I voted for ya! Good luck!

[cimtaurus]

Great ible.
I would suggest a slight change to your instructions here though. Typically you do not mentiona fration when describing amounts by parts. Use the smallest part as the base and go up from there.

Basically change "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."

to this:
Add 12 parts graphite powder (by volume) to 1 part corn starch to 4 parts 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.

I can't wait to give it a try, thanks for the instructible!

[tdavidson7]

The resulting mixture cures much faster if you add 4 parts corn starch rather than 1. But the corn starch only has an effect if you use the silicone that smells like vinegar.

[MistaStokes]

Great Instructable! I have always wanted a stylus for my phone, as I am terrible at pressing the tiny buttons, but I don't like to spend money on things unless I have to, so this is perfect for me.

[corporatelab]

Mikey77,

Brilliant. Brilliant. Mouth agape.

Everything. Oogoo the cheap (Sugru) substitute. Oogoo II conductive. Using LessEMF conductive fabrics both creatively and cost-effectively. Using double-sided circuit board as a conductive pencil. A paraffin block as a mold. Constant experimentation. You, sir, are a god.

In awe.

Good luck.