I've asked this before, but knew less about the tech and didn't word the question properly. I know other people have asked similar questions and knew little, so let me be as specific as possible here:
What I want to do is make a fine-tipped stylus for my iPad so that I can write and draw without an awkward clunky stylus that may as well be another finger.
I know there are fine-tipped styli out there, but I dislike all of them as they either do not work as advertised, scratch the screen, or are to flimsy. But most importantly: I like making things.
The sensor array in the iPad is mutually capacitive. A grid of capacitors is laid out under the glass. A constant voltage is passed through one axis of the grid. The other axis waits and detects changes in the voltage. So to trip a sensor, an object such as a human finger or stubby capacitive stylus must be brought close enough to change the voltage of one of the capacitors with its local electric field. When that field covers a wide enough area, the device registers it as input and decides where the center point is. This is how it maintains accuracy while being so low-definition.
So to reiterate: how can I make a device that generates the same electric field as a human finger over a ~5mm radius from a much finer tip? It can be ugly, hooked up to wires, even grounded to human skin with a wrist strap. I don't care about form. Just function.