I've read on various posts on the net that touchscreens lose sensitivity over time, but I have not found any detailed information about why and how I can prevent this. Does anybody know why and how this happens, and how long it takes?
Capacitive touchscreens found in modern smartphones don't wear out, physically, because they're solid-state technology behind a piece of glass. Practically the only way to destroy them is to build up a goodly amount of static electricity and then touch the screen -- if you're deliberate about this, it might zap the circuitry, but it's not specific to touchscreens and you can do that with all kinds of electronics.
Resistive touchscreens found in older electronics can wear out because they're basically made of movable things; two layers of transparent conductive material with a thin air gap in between them. Because the screen relies on physical pressure from your fingertip, there can't be a solid piece of glass in front of it (even if the LCD screen behind the touch array probably is made of glass). When your finger presses the layers together when you touch this screen, you effectively create an electrical short that is used to signal which point on the screen was touched.
- Press hard enough and you can damage these layers so that they don't move away from each other again.
- Press often enough and you'll simply wear out the outermost soft plastic material of the screen -- this is why it's important to use a clean stylus (and/or a screen protector).
I have a T-Mobile G1 (the first Android phone) that's a few years old now and sensitivity on the touch screen is still intact.
If you don't treat your phone well it is likely that over time you're going to damage it or the screen can get so dirty that sensitivity might decrease, but it is not an issue with the touch screen technology. Any phone that is badly treated will get damaged.
My Motorola Droid is as sensitive now as it was in October 2009. At least I don't notice any appreciable loss of sensitivity. This is my daily carry/drop/reflash/abuse phone, so if there were going to be some loss, it would happen by now.
In my PalmPilot days, I could definitely tell a difference after about a year, but that was probably due more to the precise poking of a stylus.
Touch screen are made with Indium Tin Oxide... and over time the Indium migrates out... so they stop working.
That is one of the reasons manufacturers would like to start using graphene in touch screens.
There are two types of screens resistive and capacative. Capacative screens are the main ones in use today and last 1-4 million touches:
That can be as little as 3 years use... which is often fine for many phones... but on the low side for something like a monitor?
Resistive screens last ~10x longer (~35 million touches).