Rolling ball for capacitive touchscreen

[Sumanta Guha]

Greetings:
I want to make a stylus for a capacitive touchscreen which has a rolling ball at the end - like a ballpoint pen. I would like to make it myself in order to get the right size, rather than try and modify existing styluses on the market.

I would really appreciate any pointers as to how to do this. Couple of points to note:
(a) The ball has to stimulate the touchscreen (of course).
(b) The surface of the ball has to grip the touchscreen, otherwise it won't roll.

A solid metal ball won't do because of (b). I tried an old style mouse ball which is fine for (b) but fails (a).

Preferable would be a solution where the ball is able to stimulate the touchscreen by itself, rather than say depending on some kind of conducting link with the case or user's hand.

Thanks in advance for any ideas.

 

[r4z0r84]

A stylus designed for resistive touchscreens will not register on capacitive sensors. Styli that work on capacitive touchscreens primarily designed for fingers are required to simulate the difference in dielectric offered by a human digit.[11]

According to a report by ABI Research, styli are especially needed in China for handwriting recognition because of the nature of its writing system.[12]

HTC patented a capacitive stylus in 2009. The design features a magnetic tip which is smaller and therefore more precise than the human finger

ref: http://en.wikipedia.org/wiki/Capacitive_sensing

Have you tried using a small magnetic ball? like "buckyballs"

ref: http://www.getbuckyballs.com/

Capacitive sensors detect anything that is conductive or has a dielectric different than that of air. Normal objects like the ball from an old mouse and steel ball will not work due to no Dielectric properties.

Hope this info is helpful.