Some of the earliest touch screens, like those in the PalmPilot or the Nintendo DS, were resistive touch screens. These screens work with two sheets of clear plastic. When the sheets are touched together, the resistance measured along both the length and width of the screens determines the location of the touch.
Because these touch screens involve actually pressing the top sheet toward the bottom sheet to register a touch, they are best used with a stylus. Dragging a finger along this screen is unpleasant if there is too much force pushing into the screen, so a screen that involves moving parts isn’t ideal for fingers. Because registering a touch is as easy as pressing the two sheets together, a stylus for this type of touch screen does not need to be anything fancier than a stick of plastic.
For some applications, resistive touch screens work great. Newest iterations of the Nintendo DS, for example, still use this sort of touch screen. Since the stylus is so thin, it is very easy to select precise locations on the screen with this type of stylus.
When capacitive touch screens came along, simple touch became a bit more complicated. On the modern phone screen, you are no longer able to register a touch with any tool lying around. These screens are designed to be touched with fingers, which will change the capacitance in certain regions on the screen. The device’s touch screen driver can pick up this capacitance difference and tell the operating system that a touch has occurred.
This works great, which is why so many phones use it these days. But some people are frustrated about having lost the ability to use a stylus on their devices. For those who owned PDAs back in the day, being unable to write or draw comfortably on the device is very limiting.
One popular solution to this problem is the capacitive touch screen stylus, which acts much like a finger for the purpose of registering a touch on a capacitive screen. These do their job okay, but they have a few drawbacks. Some lower quality styluses of the sort, rubbery at the tip, are unpleasant to drag across the surface of the screen. If there is too much friction between the stylus and the glass of the screen, many actions that would have been possible with just a finger become difficult. These styluses become appropriate only for tapping on an item instead of dragging.
Another problem is that, because of the nature of these screens, the “tip” of the stylus often needs to be as large as the finger that it’s taking the place of. Most people would expect a stylus to act like a pen, so being unable to touch anything more precisely than with a finger doesn’t quite seem productive.
A few spy on spouse cell phones, like Samsung’s Galaxy Note 5, have come out with digital styluses, which are much like the styluses you would find in a graphics tablet. These styluses are impressive in a few ways. Hovering above the phone’s screen with a stylus of this sort will display a cursor on the phone screen, because the phone can detect the presence of the stylus even from a short distance away. With Android Marshmallow, these styluses even support additional modifier buttons.
Keeping a small stylus with your phone might not be a good idea, though. You expect your phone to be portable, of course, so it might be inconvenient to keep track of an additional pen, too. Replacements for Samsung’s S Pen cost $30, so you need to consider whether or not it’s worth carrying around a stick of the sort.
Styluses mostly died when capacitive touch screens rose. But for those who really see a need, there are still options for capacitive touch screens.