It's hard to imagine that just a couple decades ago, touchscreens still sounded like something you’d only see in a sci-fi movie. And look where we are now – they’re pretty much everywhere! So that got me thinking: how do touchscreens work anyway?
More on that later, but first, I’ll tell you what surprised me the most. Get this: touchscreens already appeared way back in the ‘60s! In 1965, E.
A. Johnson created the very first finger-driven screen. Granted, it could process just one touch at a time (so, still a long way to the multi-touch displays of today), and it either registered this touch or not.
Pretty basic, but come on! It was the 60s, after all! Besides, even such a simple technology (by today’s standards, of course) had its takers.
For example, the idea had been used by British air traffic controllers till the late ‘90s! But even though Johnson was the first to create touchscreen technology, these displays hadn't gained popularity till the 1970s, when the resistive touchscreen was accidentally invented. Uh, the who-biddy what-abie, and how was it created accidentally?
I’ll get into the different kinds of displays here shortly (bear with me! ), but this incidental ingenuity happened in the US, where a research team headed by Dr G. Samuel Hurst was studying atomic physics at the University of Kentucky.
In their experiments, the scientists needed to use some equipment that was so overworked that it was only available at night. You can imagine how much that inconvenience was slowing down their progress! It was then when Dr Hurst and his colleagues thought of using some electrically conductive paper in their research.
By developing this idea, they eventually created the first computer touchscreen ever! Now the researchers could do tasks that had previously taken days to finish within a matter of hours. Further developing on that new technology, scientists at the University of Toronto invented the first multi-touch display in the 1980s.
As for the very first touchscreen cell phones, they came out a little later in the 90s. Now, all this time, touchscreens were always pretty hit-or-miss. That is, don’t imagine the really cool super fast finger movements you do on your phone these days.
But the technology was getting better and better, so you can thank these old dinosaur versions for the incredible screen you have today! So, back to the question at hand: what’s the magic behind the touchscreens we know and love today? If you thought that just one technology stands behind this "swipable" phenomenon of our time, think again!
In fact, there are more than half a dozen approaches to make touchscreens work. The two you might be most familiar with are resistive and capacitive displays. Resistive touchscreens are the simplest and most commonly used.
If you've ever withdrawn cash from an ATM, you know what they are. What about that part-time job you had as a cashier when you were a teen or each time you sign your name (or just draw a smiley face! ) when you’re checking out at the grocery store?
Those point-of-sale screens are also this type. The technology is simple: you press on the screen hard enough, and it bends and resists your touch (hence the name). But what happens next?
The thing is that a resistive screen consists of two layers that can conduct electricity. But while one of these layers is resistive, the other is conductive. And between them, there are these things called spacers.
They’re tiny dots that separate the layers until you touch the screen. So, to put it simply, an electrical current is constantly running through the two layers. Then, all of a sudden, your finger hits the screen.
The two layers get squished together, and the electric current changes. The device's software feels a change in this particular spot and does its work (meaning that it fulfills the function that corresponds with that place). You click on the $20 button instead of $50, and the ATM spits out your 20 bucks!
On the one hand, resistive touchscreens are reliable and durable. But on the downside, they’re pretty hard to read due to their multiple layers. And the more light falls on the display, the harder it is to make out what’s written there.
Ever tried to withdraw cash at an outdoor ATM on a sunny day? Forget about it! On top of that, you can't zoom in to see the little print more clearly.
Unfortunately, resistive screens can handle only one touch at a time! So, do you have this type of screen on your smartphone? Thank goodness no!
What you use to scroll through social media (or, my personal favorite: hitting snooze over and over again) is a capacitive screen. And its main difference from the resistive kind is that this screen doesn't want you to poke it with your finger. Oh no, instead, the capacitive screen changes the electric current when it comes into contact with anything that holds an electrical charge.
And by that I mean you - or rather, your skin! Just like everything else, it consists of atoms that are negatively and positively charged. Capacitive touch screens are made from either indium tin oxide or copper.
Both these materials keep electrical charges in super-tiny wires, with each of them way thinner than a human hair. But here’s where it gets a bit more complicated. The thing is that there are two different kinds of capacitive touchscreens: projective and surface.
Projective displays use a tight grid of special sensor chips. As for surface displays, they use itsy-bitsy sensors in the corners as well as a paper-thin film evenly distributed over the screen. But whichever type of capacitive screen you use, as soon as your finger hits the display, it transfers a teeny electrical charge back to your finger!
As a result, you have a complete circuit which leads to a voltage drop in a particular place on the screen. Voila! The software analyzes the location of this voltage drop and follows your command.
“Yes, I’d like to snooze for 5 more minutes, thank you kindly! ” So, ever wondered why your cell phone won't respond when you're wearing gloves? The problem is that clothes don't conduct electricity (unless you have special gloves fitted with conductive threads of course!
). And what about when your fingers are kinda wet? That causes problems with your touchscreen for the opposite reason: water conducts electricity, so the screen can’t tell where your finger is touching because the water is also grabbing some of that electric charge!
But like I mentioned earlier, even though these two touchscreen types are the most popular, they aren't the only ones that exist these days. Hey, ever heard of an infrared touchscreen? !
Whoa, fancy… Remember those action movies where the main character has to steal something from a highly protected room secured by a grid of infrared rays? Touch one of those rays, and you set the alarm off. Well, similar technology is used in infrared touchscreens.
Their displays shine infrared light in front of the screen, kinda like an invisible spider web. As soon as you touch the display, your mission's failed. Heh-heh, just kidding!
You’ll just interrupt a couple of the infrared rays, and it’ll set up a reaction. By analyzing which rays you've interrupted, a microchip in the screen will then know your intentions. Most e-readers have screens like that, by the way.
Here’s one that sounds super fancy: surface acoustic wave touchscreens! To detect your finger, this technology uses sound, not light. (Ah, fancy functions for its fancy name!
) The screen creates ultrasonic sound waves at its edges, and they get reflected back and forth all over its surface. As soon as you touch the screen, you not only disturb the sound beams but also absorb their energy! That's how the built-in microchip controller understands where you've hit the screen.
Don’t even bother holding this type of screen up to your ear; these ultrasonic sounds are too high-pitched for your human ear to hear! One more type of touchscreens called "near field imaging" is so tough that it's suitable for the most challenging environments. That's why it's widely used in the military.
When you move your finger closer to this screen, you change the glass screen's electric field. As a result, it immediately recognizes your touch. Such technology allows you to control the screen with the help of a pen, stylus, and even while wearing gloves!
By the way, most people don't realize just how widely used touchscreens are! In fact, nowadays it's hard to find a field that doesn’t make use of them. Airplanes, stores, banks, schools and universities, hospitals, you name it!
Also, these days, with the help of special devices, you can turn literally any surface – be it your desk, a wall, or even your skin – into a touchscreen! So, do you think new types of touchscreens will appear any time soon? Let me know down in the comments!
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