I recently purchased a stylus for my iPad2. I shopped around and finally decided on a Touchtech. The pen has a retractable ball-point at one end and the stylus at the other. The big, fat tip bothered me a bit (I used to use a Newton, which has a much more delicate and precise stylus!) and so I wrote to the company to find out why it had to be so obese.
Jerry Leto at Touchtech responded right away. I now have a much better understanding of the screen technology and thought I would share his response with you, with his permission of course. I found it very informative.
Being new to capacitive touch technology and all of its wonders, and shortcoming, can be tough at first. You hit it dead on with the statement that it is a function of the technology. Oh, the Newton. Lots of great features to that product, I must say. Here is the nuts and bolts of iPads, etc. (Multi-Touch Capacitive Touch Screens). They work by capacitively coupling to the human body, are designed for interaction with fingers and have a very specific range of size they detect. If you are curious, you can Google search Brian Huppi, the guy who designed the tech for Apple. He is actually an associate of mine. In other words, if they were to detect a small area, such as a pen nib (1mm), when you press your finger to the screen it would detect a multi-touch and it would confuse the software. Generally speaking, it is about 4.5mm and anything smaller, or larger than say 6.5mm, wont trigger or drive the device. The reason for the squishy, is that if you hold the device to eye level and slowly press your finger to the screen, you will see a depression left in your skin of approximately 4.5mm. Harder materials or anything that will not quickly conform to the 4.5mm diameter circle, have issues operating/driving the devices. Those tips I designed are to depress as easily as your skin would so you get a very fast and accurate response from the screen. I also designed a coating for the tips to more closely replicate the drag of the human finger on the screen. Many styli actually have a very high drag or chatter and people really hate that, me included. You also have to push really hard to make them work, and I tried to engineer the TT II pen to work around those common complaints from consumers. I am not sure if this answers some of the questions you have, but if you have anything else you would like to know about the tech, please call or email me. I have no problem answering your questions to the best of my ability.
I have nothing whatsoever to do with Touchtech and have never met Mr. Leto, but I was impressed by this outfit's commitment to customer satisfaction. (Elsewhere in his message he mentioned that if I was dissatisfied in any way with it he would refund my money immediately.) I really like companies that go the extra mile for their customers.
Here's the company's website... Touchtech - Home
And here's where I bought mine... Amazon.com: touchtec pen