Refining the Concept

Now I had an O-shaped contact, a hinged connection that did not interfere with the line of sight, and a contact surface that was durable and did not scratch the glass.

 Some early hand-made prototypes using etched brass handles

I then worked through a lot of prototypes using 3/8" brass rod, trying out different lengths. One major hurdle was figuring out how to attach the wires to the handle. I knew the contact O would be held in place by the tension of the two wires, but soldering them to the handle meant the metal would lose it's spring-hard qualities. Crimping or crushing the wires into holes proved to be the best solution. It preserved the temper of the steel wire. But the thinness of the brass handle bothered me. It didn't feel very pencil-like. But if I made it out of 1/4" brass rod it proved to be too heavy. Aluminum ended up being a great solution because it is so light weight, but also a great conductor, and easy to design a crimped connection with the wires. It felt like the same size as a pencil, and only a little bit heavier.

Early handmade prototype O with steel wires

But aluminum's main problem (at least when you hold it in your hand) is that it can discolour, unless it is anodized. Anodizing involves immersing the aluminum in sulphuric acid while a current is put through it. Because the thin anodized layer is brittle, I had to anodize after the wires were held in place, which meant the wires had to be immersed in the acid. Stainless steel actually rusts in this situation, but titanium does not. Titanium can also be hardened, and it doesn't corrode, so that ended up being the perfect choice for the wires.

All that was left to do was find a way to make the contact O without soldering the tube hinges onto the O. At first I tried a lot of flat O's with tabs that could be bent, but the best resolution came through a combination of CAD and machine shop experiments that almost duplicated my early handmade ones.

Present oStylus model, 2011

Next steps...

Second in a series of blog posts about the development of the oStylus

After I had designed a basic rigid stylus with a hole cut out, I then went on to deal with a couple of problems. The first one was that the contact between the glass and the metal didn't feel smooth and I was concerned about the possibility of scratching. The contact O needed a smooth surface, soft enough not to scratch the glass (which, by the way, on an iPad or an iPhone is harder than most metals) and tough enough to last. I tried everything from packing tape, to masking tape, to thin leather, felt and flocking. It had to be soft and slippery, and also thin enough not to interfere with the capacitive touch system.

It took several months but in the end I settled on vinyl film, the kind they use on car and bus advertising. It's soft and flexible and extremely durable (outdoor warranties are for 4 years of rain, snow and sun), and it's also self-adhesive.

Using some artists as testers for these prototypes, I soon discovered the second problem. Yes, the O allowed you to see what you were drawing, but each artist had a particular angle they held the stylus at, and if the O didn't lie flat against the glass, it wouldn't register as a touch. I had settled on 45 degrees as a good compromise angle. But what if you normally drew using a pencil at a 60 degree angle, or signed your name holding a pen at 35 degrees? I had to make the connection between the O and the handle that was flexible or hinged in some way.

 Early hinged prototype, April 2010

The first prototype solution used a three-tube hinge soldered on top of a metal O. It seemed logical to put the hinge on the edge so you still had a clear line of sight through the O. This solution worked if the washer contact was heavy enough to flop against the touchscreen with gravity, but it was frustrating because the pushing action to make the contact was off-centre.

This problem led to a contact O with two tubes soldered to the top, in the middle of the O. The pin for the hinge was split so that you had both a clear line of site through the O, and when you pushed down on the O to make contact it naturally lay flat against the screen. The pin wire could become the connection between the handle and the O. The contact pad could also be a thinner lighter weight. This designed allowed the natural hand position I was looking for.

Next early prototype with a two-wire hinge, temporarily attached, April 2010

Now I was really beginning to get somewhere: I had a conductive stylus with a hinged contact pad that allowed you to see through a hole in the middle for more precision than a foam-tip stylus. And the pad had a safe contact surface which glided smoothly on the glass. But there was still a long way to go. More in the next blog post.

Legal note: I am pleased to be able to share this information, but it is my intellectual property. The name oStylus is a trademark, and the ideas in this invention are Patent Pending. 

What is this?

The oStylus, a stylus for capacitive touchscreen devices, already has a website. So what's this blog for?

Good question. My aim is to let you look behind the formal website information to tell you what we are doing and how we are thinking; to allow visitors and buyers of the oStylus to comment; to give some explanations of why things work the way they do. I hope it will also serve as a record of what we have accomplished in a very short time.

It was only about a year ago that I was struggling with drawing on my iPod touch with my finger. I was using the PaintBook app, and getting tired of zooming in and out to enable me to accurately draw a line, placing it where I wanted, and not have my finger constantly in the way of what I was drawing. I also knew that I didn't grow up drawing with my finger — I was always holding a pencil or a crayon or a paintbrush. I knew there were styluses out there, but they all looked and acted like small fingers, blocking the screen. So my first question was: how small can the contact area be and still work?

I'm a jeweller — not a retail jeweller — but a designer, a maker. Most of the jewellery craftspeople I know are great problem solvers. They work with hand tools and machine tools, they know multiple materials and their characteristics (for example I work in silver, gold, plastics, concrete, bronze, paper) and the best ones know metallurgy. They know how wire bends, how metal can be forged or cast. So when I encountered the iPod sketching problem I immediately thought of metal solutions and went to our studio to work it out.

My first attempts were pretty funny. I took 3/8"" brass rod, forged the end flat, bent it and filed it smooth. It had a  primitive-tool feel to it but it worked. I knew the stylus had to be conductive because capacitive screens work by sensing capacitive differences between the screen and the finger. Once I had the smallest possible circle contact working, I realized I wasn't much further ahead than the foam-tipped styluses out there. That's when I hit on the idea of seeing through the contact pad. If I cut out the centre of the circle would it still work? I cut out brass washer shapes and soldered them on the handles, trying different hole sizes and edge thicknesses until I had the best compromise between
    1. being able to see the screen clearly and
    2. still having enough metal to imitate a fingertip.
I ended up with a  stylus that worked. I could see the line as it was being drawn in the opening of the contact pad.

Here's a picture of some of the early experiments from Spring 2010:

Three early prototypes made of brass, copper and various contact materials

I liked what I had developed, and it was usable, but there were still more problems to solve. I'll write about those soon.