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How Touchscreens Work


In our last article we told you all about how LCD screens work. In that piece, we talked a little about the history of LCDs and how important they’ve been to the rise of personal mobile electronics like smartphones, tablets, and laptops. Today we’re going to talk about another crucial component of this technological revolution: the touchscreen. The first touchscreens were designed in the 1960s, but the technology was expensive and imprecise. It wasn’t until the 1990s that there were serious attempts to bring touchscreen technology into the consumer world. IBM was the first company to attempt to bring the technology to mobile phones, with the Simon in 1993, while Sega made an aborted attempt to incorporate touchscreen technology into mobile gaming. It wasn’t until the early 2000s, with the introduction of PDAs and early smartphones, that touchscreens began to see use in mobile electronics.


Pretty much all modern touchscreens fall into two basic categories: resistive touchscreens and capacitive touchscreens. Now, within each category there are a ton of different kinds of screens, all using slightly different technologies, but this is a basic overview of touchscreen technology, not an in-depth academic paper, so we’re just going to stick to the two basic categories.

Resistive Touchscreens

While resistive and capacitive touchscreens were invented around the same time, back in the 1960s, resistive touchscreens were the first to see common use in mobile electronics. PDAs and early smartphones used these screens. A resistive touchscreen is constructed in layers. Most of these layers can vary depending on the technology, but the crucial part is the two in the middle. Every resistive touchscreen has a two transparent layers - one conductive, one resistive - separated by spacers that keep them from touching each other. Each layer has an electric current running through it. When you touch the screen, you close the gap between the two, and change the flow of electricity at the point of contact. The device’s software notes the location of the change, and engages whatever action is associated in with that part of the screen.

Resistive touchscreen technology has a few advantages. For one, it’s less expensive than capacitive touchscreens, and requires less electricity to work. For another, there aren’t any restrictions on what you can use to interact with the screen. You can use pretty much anything to operate the screen - a simple plastic stylus, a finger (with or without gloves), or just about anything else - since all you have to do is close the distance between the two layers in the middle. Many modern devices like ATMs still use this technology, precisely because it’s less expensive and consumes less power.

The main drawbacks with resistive touchscreen technology are that it limits screen resolution and it can’t recognize inputs from multiple touch points at once. That’s why when Apple decided to kick off the modern smartphone era with the iPhone in 2007, they used capacitive touchscreens.

Capacitive Touchscreens

As with resistive touchscreens, there are a lot of different kinds of capacitive touchscreens, but again, in the interests of brevity, we’re just going to focus on the basic features of the technology. Capacitive touchscreens mainly consist of a layer of glass covered with a transparent conductor. A uniform charge is applied to the glass at the corners. When anything that holds electrical charge - like your finger - touches the glass, the electrical field is changed. The screen detects the location of the change and communicates that information to the device’s software, which engages whatever function corresponds to that location on the screen.

As previously mentioned, capacitive touchscreens have two main advantages over resistive touchscreens. First, they can recognize multiple simultaneous touches on the screen. That’s why you can, for example, use two fingers to zoom in on a photo on your phone’s screen. Second, they allow for much better image quality. Resistive touchscreens put multiple transparent layers between your device’s LCD and your eyes. Those layers refract light and reduce image quality. Capacitive touchscreens only require a single layer of glass, so the light from your LCD has an easier path through the screen to your eyes.

While capacitive touchscreens have a lot going for them, they do have one major disadvantage over resistive screens: because they’re made of glass, they can crack, break, or even shatter. In other words, the most important component on your smartphone is also one of the most vulnerable to damage. That’s where we come in. At Phone Medics Plus, replacing touchscreens is one of the most common jobs we do. So if your screen is damaged, you can call us, schedule an appointment online, or bring it to our repair facility at 91 E. Merritt Island Causeway in Merritt Island, where our experienced technicians can get you tapping away on your touchscreen again in no time.

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