What Type of Pen Will Write on an Apple iPad?

Two primary types of touch screens exist in consumer devices: resistive and capacitive. Resistive touch screens have two layers in their screens that generate a current when they are pressed together. These screens require a hard, narrow pressure to work. In contrast, capacitive touch screens, such as those used in iPads, use a finger's electrical conductivity to disrupt the screen's own electrostatic field. Capacitive touch screens have a hard covering and do not require pressure to work, but they cannot be controlled through gloves.

For a stylus to work on a capacitive touch screen, it must conduct electricity similar to a human finger. To do so, most capacitive styli use soft silicon rubber tips that deform when pressed against the screen, similar to a fingertip. Pogo, Wacom, Griffin, among others, produce these tools in a range of styles and sizes. Styli with narrow tips allow for more precise control, while those with wide tips better emulate direct finger taps.

Resistive touch screen styli do not work on an iPad. You can identify these styli by their narrow, penlike tips, which are usually made of hard plastic or metal -- such as the styli included with the Nintendo DS and older-style palm devices. Active styli, used in combination with graphics tablets, also do not work on the iPad, as they require special hardware built into the writing surface.

Several types of iPad styli exist for alternative uses. For drawing and painting, there are styli designed with a brushlike or wedge-shaped tip, and others that have a clear tip that allows you to see a line as you draw it. There are also a variety of other special styli, such as telescoping styli, styli worn on the finger, marker-shaped styli for children and even a guitar pick-shaped stylus. As long as the product indicates compatibility with capacitive touch screens, any nonstandard stylus model will work on the iPad.