How Do Touchscreens Work?

How Do Touchscreens Work?


Touchscreens are everywhere. Not just in smartphones,
but in supermarkets, ATMs, and even airplane seats. And you may have noticed that not all touchscreens
are the same. The old-school touchscreens can be pretty
tough to use — sometimes it feels more like a push-really-hard-screen instead of a touchscreen. On the other hand, certain smartphones and
computer monitors are really responsive to many different touch patterns. There are lots of different technologies out
there, but they’re all trying to achieve the same goal: sending precise electrical
signals from specific locations on the screen. One of the most widely used types is the resistive
touchscreen, where you have to physically push and bend the screen to make it work. Resistive touchscreens are made of two separate
layers: The top layer is made from a flexible and
transparent material, such as polyethylene, which is a common plastic used to make things
like soda bottles. And the bottom layer is made of something
more rigid, like a sheet of glass. To make the screen work, both of these layers
are thinly coated with some sort of metal compound that conducts electricity, like indium
tin oxide — which is commonly used because it’s transparent. These layers are also separated by tiny insulating
dots, which /don’t/ conduct electricity, called spacers. They keep the screens apart
to make sure there aren’t any false touch signals. When the screen is on, a small voltage is
applied across the screen in both the horizontal and vertical directions. As soon as you push down on the flexible screen
with anything, like your finger or a stylus, it connects the two layers together. This changes the voltage, and a small processor
connected to the screen can calculate exactly where you pressed in X and Y coordinates. These resistive touchscreens are pretty affordable
and durable. So, they’re useful for things like credit
card readers in grocery stores, where you need to capture touch data of a messy signature
— over and over again. But they can be a little frustrating to use
if you don’t push hard enough. Plus, they normally can’t understand multiple-touches
at the same time – so they’re no good for two-finger zoom or more complex tasks. That’s why these days, most smartphones
rely on capacitive touchscreens, where your finger becomes a key part of the electronics. There are different kinds of capacitive touchscreens,
and they can vary from device to device. But one basic design is a sheet of glass containing
a grid of hair-thin lines of a conductive metal, like indium tin oxide. The grid lines in one direction are called
the driving lines, which provide a constant electric current. And the lines in the other direction are called
the sensing lines, which detect this electric current. At every point where the sensing lines and
the driving lines cross, there will be a specific electrostatic field, which is registered as
neutral by the processor in your smartphone or computer. But that all changes when something conductive
comes along and touches it — like your finger. See, the human body has a natural capacitance,
which means our bodies can conduct electric current, and can store electric charge. So when your finger touches the screen, the
charge in the screen is drawn around that point, distorting that electrostatic field. The electricity doesn’t actually /flow/
through your finger. Basically, the electrostatic field feels the effects of your electric charge
and redistributes itself accordingly. Even really small changes are detected by
the processor, which can then interpret the patterns you’re making – whether it’s
a tap or a slide. Because the lines of the grid are so thin,
capacitive touchscreens are super accurate, and some versions can process multiple touches
at a time. But they won’t work if you have gloves on
— because the cloth isn’t conductive, unless your gloves have those special fingertips
with metal fibers inside. Plus, something like sweat can affect how
electricity is conducted across the screen, because it’s full of salts. It’s all about the materials that can affect
the electrostatic field generated inside your screen. So next time you’re texting on a smartphone
or scrolling through internet forums on a tablet, just remember: you’re actually a
part of the electronics making it work. Thank you for watching this episode of SciShow,
which was brought to you by our patrons on Patreon. If you want to help support our show,
you can go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow and subscribe!

100 thoughts to “How Do Touchscreens Work?”

  1. I have nerve issues in my extremities. After having a nerve conduction study done on my muscles i learned that my muscles dont produce much electricity. Is this why sometimes my numb fingertips don’t seem to make the connection i am trying to make on a touchscreen?

  2. If you use hidrophobic sprays on touchscreens,would the touch screen work underwater?Or it will be the same result?

  3. wait the what about screen protectors. if iPhones us capacitive screens why does my iphone work with a layer of plastic above.

  4. A really big opportu ity you missed was tl tall about how galaxy s5 touch screen touch sensatovoty can be increased: allowing to use almost any glpves or pencils and pens to uae the tpich scree .

  5. I have a Sony xperia z3+ it has Heat Detection. So if there is salt or water on the screen it doesent sense it butwhen your warm finger touches it it registers.

  6. Im looking for a way to simulate touch screen that can control with a device like a raspberry anyone out there know

  7. One time I couldn't use my touch screen phone when my fingers were really cold. It would not go.

  8. So, as the saying goes (typically in reference to electrocution), "we're completing the circuit"?

  9. What about using a plastic bag? If you put your phone in a plastic bag the touch screen still works. Can someone please explain how?

  10. Yu told me that the display screen having two parts one is with flexible by that we have to touch exactly x and y..and now my doubt is what about the temper

  11. thanks for this video … my questions that if touch using by any conduct material..its should be work right… but i tried operate to the screen by conducting material like bold screw
    its dosn,t works..

  12. A type of touch screen I have used is an old IBM one for their cash registers. It works by having a vertical and horizontal laser grid with sensors, and when you disrupt the grid, it knows an x and a y to click. Its neat, if a bit bulky and prone to error.

  13. Does touchscreen sensitivity decreases on a capacitive touchscreen when too much pressure is applied on it by human hand/fingers?

  14. The whole thing is stolen from a blog explaining the same thing. Man you could have searched it more and add some more information but no….

  15. I have pocket so I can put my phone underwater. However when it’s underwater, the touchscreen doesn’t work. Why?

  16. I have a twenty dollar desk lamp that has touch buttons. The four buttons are, on/off, type of light, up and down on the brightness. It's just a cheapo lamp, but also has a cloak with an alarm, and thermometer. The buttons are painted on, and you don't have to touch them, just hold your finger above the painted button. Just wondering how it worked.

  17. They need to put a 1/2 second pause between the edits…holy crap, its like the guy did this without breathing. I'm out of breathe and stressed out. Good info tho.

  18. Very interesting and informative; thank you so very much! I was an aviation electronics tech in the Navy back in the 80s, and touchscreens had not been invented yet. Now I use a touchscreen many times a day, not only on my phone, but on the CNC equipment I am tasked with repairing (no aircraft unfortunately). Foolishly, I have not kept up with technological advances, so this is one of those things that has eluded me.

  19. If gloves are thin enough, you can still operate a capacitive touchscreen. Examination or laboratory gloves like those made of latex or nitrile are thin enough to allow one to still operate a smartphone, albeit with a slight bit of difficulty.

  20. I'm studying to be a nuclear electrician and I thought "How do touchscreens work?" Then I remembered measuring voltage across my body and I was like "That has to be it." So here's to 2 years of school and me messing around with test equipment to be able to come to the correct hypothesis of how my phone works.

  21. 3:00 what? conductive material.? will the touch screen work by touching with any conductive material? fact is..it doesn't working other than live human body..! why?

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