The everyday technology we all take for granted
There’s more to touchscreens than you might think!
This all started when I was on my phone one day, and I wanted to make a DIY stylus. Turns out, this is not as easy as you would think, since touchscreens are only sensitive to certain materials. But why is this? How does a touchscreen know whether its a finger touching it, or a piece of cardboard? In fact, there’s a lot more to touchscreens than you might think!
Before we answer the “burning” question, we need to clarify a few things first. There are 2 main types of touchscreens: capacitive touchscreens and resistive touchscreens (or as I like to call them, ‘smack it until it works’ screens). Your smartphone probably uses a capacitive touchscreen, unless you’ve traveled from the past and not caught on to the new major trends. Then you’re probably running a resistive touchscreen. (FYI, we haven’t found the aliens yet).
Resistive Touchscreens
These are the kind of touchscreens you would find on cashier registers, old smartphones, printers, and some airplane entertainment systems. Resistive touchscreens have 3 layers: 2 layers of a flexible conductive material separated by a thin layer of air in between. Due to the layer of air, electricity can’t flow between the 2 conductive materials. When you press the screen, you are forcing the 2 conductive materials to touch, and the electric current passed between the 2 materials is registered as a press.
Because you have to deform the material these screens often take a lot of force to register a press, which is why they aren’t used as much anymore. If you ever get mad because a touchscreen is not working, it’s probably a resistive touchscreen.
Capacitive Touchscreens
Capacitive touchscreens are modern touchscreens. These are the touchscreens in modern smartphones which are so seamless to use. They have a grid of conductive material in 2 different layers, one connected by rows the other by columns. Imagine diamonds overlaying each other in the shape of a lattice. One layer is negatively charged, so the electric field expands around each diamond. When your finger touches the screen, it distorts the electric field, which is detected by the device.
The first capacitive touch screen was actually made in the 1960s. But of course nobody thought that a device with an integrated touchscreen was a good idea until 50 years later. Shocker! 😱
Why do touchscreens only work with some materials?
Okay, to be clear, capacitive touchscreens are the picky ones. Resistive touchscreens should work with any material, since you just need to slightly deform the screen. On the other hand, capacitive screens only work with materials (such as your finger) that conduct electricity well. This is how it detects the distortion of the electric field around the screen. It’s also why most stylus’ are made of a rubbery material.
Sadly, erasers don’t work on touchscreens (yes I tried it).
