Homebrew iPod Touch Stylus

So, I finally have an iPod Touch (4G) that my darling wife got me for my birthday a few weeks ago. I'd been holding off on getting an iPod for years now, avoiding the Apple plague as long as I could. There are several reasons for my "Apple apprehension" (or "AA", if you will), but the biggest one is probably the difficulty I've had in dealing with Apple's "popular kid" persona. As a professional designer, it's always rubbed me the wrong way that the design of so many electronics these days have mimicked the Apple design language...as if they were the only ones who could speak "design-ese". The neo-modern aesthetic is nice, but, come on...there are so many more possibilities out there! Why do marketers get the final say in what gets put out there for the general public? So, out of principle, I've stayed away as long as I could. I think what finally made me give in was the capabilities of the newest version of the iPod Touch...and the many how-to sites out there on how to hack, modify, and customize it. Since my masters' thesis was on user-initiated product customization (and its broad affects on industrial design), I though it only fitting that I should take a crack at customizing my own device. And since Apple ("sigh") has built the iPod with enough quality and desirable features in it, I've now got an electronic product that I feel is actually worth customizing. Go figure. And with that little rant-of-the-day, we move into my first posted project: a homemade stylus for the iPod Touch.
Since so much of my daily work routine involves the use of a pen for sketching and visual communication, I knew I'd quickly find a need to use a stylus with my iPod as I scribbled out ideas on a sketching app or two. I wasn't too keen on buying one of the several stylus offerings already out there, mostly because they just seemed a bit, well, wussy. To be honest, I've got big ol' ape hands, so a stylus with substantial proportions is high on the priority list. After searching for hours online without success, and even seeing what others had done to make their own styli, I though I'd take a crack at learning about the tech behind the capacitive touch screen interface and make my own stylus from scratch.
After some study and experimentation, I (and a colleague) found that any stylus for use with the iPod must at least have the following traits: a non-abrasive, conductive tip (with a proper level of electrical resistance), sufficient surface area, and it must provide electrical continuity up to the user's fingers. After testing out some styli out there, I determined that I preferred a semi-rigid tip, because it felt more like the marker and pen tips I was used to--so that meant a squishy, conductive foam tip was out of the question (sorry, Pogo). With a little footwork, I found that carbon fiber fabric works very well as a media for use at the end of a stylus because in a raw state (without resin impregnation) it wasn't abrasive and had the perfect level of conductivity. Since I've got a decent supply of carbon fabric in my office (as carbon composites are one of my specialties) I thought I'd do some testing and build a simple stylus using a rubber-gripped mechanical pencil as a test piece. A cheap little Paper Mate pencil seemed to fit the bill well.

I took the pencil apart completely to get a view of what would need to be modified to make the stylus:

The carbon cloth I'd be using was very flexible (a 1K, plain weave, if you want specifics), so I determined that I could cannibalize the eraser that came with the pencil to act as a semi-rigid support behind the cloth to give the stylus the proper "feel".

Next I had to modify the tip of the pencil a bit by using some 80-grit sandpaper (followed by 600-grit for smoothness) to sand down the threads at the end of the barrel where the tip originally screwed on:

  I trimmed a lip onto the eraser so it would fit into the tip of the pencil without sliding too far into the barrel...

...and then cut off the excess eraser, leaving only enough to create a rubbery-feeling tip:

I then used the sandpaper again to round over the tip a bit...

Next, I trimmed a piece of the carbon fiber cloth into a 1.5" diameter disc that could be wrapped around the tip of the pencil...

...and then used some tape to adhere it to the pencil barrel. Note that I've left some space at the tip so that I can add conductive material (aluminum tape) where the fingers grip the pencil.

The conductor I used for this test stylus was basic, off-the-shelf duct sealing tape--an inexpensive aluminum foil with a peel-off backing and crazy-sticky adhesive.

Since there is adhesive on one side, it won't simply conduct through that adhesive to the finger-contacting side. So, I folded a small edge over to act as a contact strip between the carbon cloth and the user's fingers:

I then put this over the already taped-up carbon cloth tip, ensuring that the contact strip actually touched the cloth:

To further ensure good connectivity with the user's fingers, I used some 600-grit sandpaper to remove the lettering on the outside of the aluminum tape:

The last step required trimming the rubber grip that came with the pencil to allow finger contact through to the aluminum tape. This rubber grip would also hide some of the "hacked" look of the stylus. As cheesy as it looks, I tried to put at least a little ergonomic shaping into the grip cutout so it wouldn't feel too funny after prolonged use:

Lastly, I slipped the rubber grip over the tip...

...and then gave the stylus a whirl. As long as you touch the aluminum with one fingertip, the stylus works flawlessly (as seen below with this SketchBook Express app)! My colleague was envious of the feel, having settled for a Pogo stylus before I ventured into this little build. That'll teach him.

The next step in this development process will be to use what I've learned to create an even "sexier" stylus...one that uses the same tech guidelines, but with a much more attractive stylus shape. I plan on turning a new barrel on the lathe in our shop out of steel (for good weight balance on the inside) and aluminum (for corrosion resistance and conductivity on the outside), while still using another rubber grip with appropriate modifications for finger-to-tip connectivity. I may even do a design with an all aluminum barrel that uses a tungsten core (made from rod used by our tig-welder) for a good weighty feel in a more compact package. After all that, I guess all I'll have to do is get used to writing on such a small screen (...at least until somebody comes out with a reasonably sized and priced device that touts a "Cintiq-esque" pressure-sensitive screen and other designer-desirable specs.) :)