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I know that tapping on the screen with an object doesn't cause any reaction in the user interface (e.g. it doesn't cause a click of a button shown from an application). To what is the iPod's screen sensitive, and what can I use to replace my fingers?

The problem I am trying to resolve is that, using my finger to play a game, I don't see part of the screen, and my finger hits something that causes the game to end (you know, those little bombs that are launched in the play field when you are trying to slice fruits).

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5 Answers 5

up vote 4 down vote accepted

Something conductive and either soft or flat will register with the capacitive touch screen sensors. A ball of conductive foam or wadded up aluminum foil, or even a half inch strip of the metallic insides of a power bar wrapper.

There are several manufacturers of iPhone stylus's that use variations of the above. You can google them.

Non-conductive stuff won't work. And anything too pointy will also have problems being recognized, as there won't be sufficient electrical field coupling.

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Along those lines, water is conductive, which is why the screen can go loopy if you try it use it in the rain or if your hands are wet. –  Reid Nov 9 '11 at 1:57

Sausages work very well! (not kidding)

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Now, should I take you are saying my finger is bigger than a sausage? :-) –  kiamlaluno Nov 7 '11 at 19:36
    
Actually I don't know your fingers :-p –  Max Ried Nov 7 '11 at 19:39
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Oh heck, even a wurstel is bigger than my fingers (except my thumb). :-) –  kiamlaluno Nov 7 '11 at 19:44
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So then accept it as a tip for using iDevices while wearing gloves. –  Max Ried Nov 7 '11 at 19:51

Anything that generates an electric field. Your finger generates an electric field, so it generates a "click" on the screen. Here is a good article on the iPhone's touchscreen.

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Not quite - you need a voltage difference to generate an electric field. Your finger doesn't have that, so it can't generate an electric field. Rather, the screen essentially contains an array of capacitors, and if your finger is near one of these capacitors, it changes that capacitor's capacitance. That change is what's detected. –  Reid Nov 9 '11 at 1:56

All answers thus far are somewhat inaccurate or vague. A more detailed answer:

Apple's touchscreen devices and trackpads use capacitive touchscreen sensing. This technology measures capacitance on a grid of points. When a capacitance within a certain threshold of human skin is met, the software reacts to the touch input detected in those points on the screen.

This is opposed to, for example, resistive touch screens, which are generally used in older or lower-end electronics. These have a slight squishy feel on the surface, and are much less responsive than capacitive screens, but work with any object as a stylus. This works by having two films of conductive grid lines. When an object causes a depression in the surface which pushes the two layers together, the point of contact can be measured by comparing the resistance of the various grid's lines.

Having made this distinction, any object used to interact with a capacitive touch panel must have a similar capacitance to that of skin. Things such as meat would work (sausages were suggested), but aren't very practical. However, styluses made to work specifically with these screens can easily be found online. Those might be the perfect solution for you, since they're like a long thin pen used for the touch screen that doesn't obscure your view as much as fat thumbs might.

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Battery!!!! (Negative side only)

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Can you please explain what you meant here and how it relates to the question? –  patrix Feb 9 '13 at 5:57

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