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Why not make a tablet stylus with a potato chip bag?

April 17, 2016
aluminized-mylar-capacitive-screen-01

The aluminized side of a Mylar film bag is conductive enough to about 3 cm.

My technical research arm (the left one—I’m left-handed, after all) continues to look into ways of making a stylus for a capacitive touch screen tablet. The goal is to make the stylus out of freely-available materials found in the garbage and thus avoid the absurd $10-$30 cost of a store-bought capacitive stylus, which I know is little more than an electrically-conductive metal barrel tipped with a tiny piece of similarly conductive foam.

How a modern touchscreen conducts itself these days

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Electricity flows from my fingers down the folded aluminum-coated Mylar film.

Modern capacitive touchscreens exploit the fact that the human body both creates and conducts electricity. The lightest brush of a finger on a capacitive screen is like the closing of an electrical circuit. This approach differs from the touchscreens of a decade ago, which were resistive, meaning that they reacted to the pressure of anything, including fingertips.

Resistive touchscreen devices, like the old Palm handhelds, were grouped under the category of “pen computing” because, although they could be controlled with fingers, they could be controlled more precisely using their included plastic stylus.

For its ground-breaking iPhone in 2007, Apple implemented a capacitive touchscreen that dispensed with the annoyingly easy-to-lose stylus, without sacrificing much precision.

It’s fair to say that the stylus-based resistive touchscreen became obsolete overnight.

However, there will always be some tablet-based activities that benefit from using a stylus: illustration, diagramming, handwriting and cold-weather use with gloves all come to mind. And besides, there are sticks-in-the-mud, like myself, who just want a stylus because.

So what kind of things have the capacity to be a stylus?

A stylus for a capacitive screen has to conduct electricity from the fingers holding the barrel all the way through the tip, which is the tricky part because this has to be made of a material that both conducts electricity and is soft enough not to scratch the screen.

Typically, but not exclusively, a capacitive screen stylus is tipped with a tiny square of conductive foam, which is commonly used in the packaging of computer chips.

There are any number of ways detailed online to make a capacitive stylus if you have this type of foam—my favourite is to stick the foam in the claw end of an old steel mechanical drafting pencil.

So far though, no amount of scouring computer store dumpsters has yielded me any discarded conductive foam, or special conductive fabric or conductive rubber for that matter. I keep an eye out for this kind of stuff but I’m also interested in identifying any other freely-available soft materials that can conduct electricity.

Besides conductive foam, many DIY stylus approaches rely on using a damp cotton swab, by itself or stuck into the end of a pen barrel. The swab is electrically connected to the fingers holding the pen by some kind of conductor—a winding of copper wire or a wrapping of aluminum foil.

Otherwise, I know that you can use carrot sticks but that they don’t work indefinitely. I would also expect that celery sticks would be just as effective. In fact, a small grape stuck on the end of a long nail should work—but I haven’t actually tried this.

Rolled-up screen protector plastic is said to work a charm, as well as the plastic from anti-static bags that computer boards come it.  Another thing that I haven’t tried, that supposedly works as a conductive stylus tip (hard as it is to believe), is the soft yellow sponge part of a ScotchBrite scrubbing sponge.

I can say from experience that the anti-static sheets from old cassette and video tapes do not work and neither does the aluminum oxide-coated tape itself.

Playing around with stuff is just my bag

A Mylar clothing product bag with one side aluminized.

A Mylar clothing product bag with one side aluminized.

Mylar plastic film, which has thousands of industrial uses, is not, by itself, an electrical conductor; it’s an insulator. However, the shiny metallic Mylar film that is commonly used for packaging–especially of food (think potato chip bags) is conductive, thanks to the fact that the shiny coating is aluminum.

My two experiments with aluminized Mylar have so far shown that it doesn’t conduct the charge from your fingers to the touchscreen over a distance much greater than 3 centimetres, which is kind of disappointing. However, I’m thinking that I might find some aluminized Mylar with a thicker coating of metal that is that much more conductive.

We could say that I’m looking to save money, or that I’m playing around—neither would be a lie. But it would be closer to the truth to say this is one of the games that I play in order to get a deeper understanding of how the technology I use actually works. It’s like a hacker thing basically. Click the images to enlarge them.

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From → Android, Apple, Computers, Palm

3 Comments
  1. Dawn permalink

    I have found styluses appropriate for touch screen phones for $3 at Dollarama. They look like pens with foam on the ends. Though your method is certainly more creative and educational.

    • Dollar store rarely figure in my calculations for computer stuff because low quality cables and such can often do more harm than good but I can’t see how this could apply to a touchscreen stylus.

      The closest Dollarama to me in Vancouver, B.C, is in the 2200 block of Kingsway. I’ll try to check it out. Thanks.

  2. Very informative and well written. Thanks a lot : – )

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