Touch screens, touch screens, touch screens.
Well, they are everywhere and I love them. I disapprove of Apple for not being able to provide a touchscreen laptop yet. But I don’t care so much because I don’t use a MacBook anyways. Touch screens are so common today, it should really not be something I have to look up in the specs. when I buy a new gadget. But this is not about Apple. I was curious about how touch screens work, so here it is.
Before touch screens, we had keyboards, mice, and a bunch of other types of peripheral devices, which often introduced chances of errors and distraction when interacting with a digital screen. So, this technology really originated from the need of more direct interaction with data and other digital elements.
Well, fundamentally, both keyboards and early touch screens operate on a similar principle: completing or altering a circuit to send a signal that an input has been made.
In a keyboard, when you press a key, it completes a circuit allowing the processor to recognize that a specific circuit has been completed. Basically, a switch.
The early touch screens were mostly using resistive technology, where two thin layers of flexible plastic film or glass, both coated with conductive and resistive metallic material (like Indium Tin Oxide) face each other. What keeps these two layers separate are Spacer Dots, allowing the top layer to be flexible and make contact with the lower layer. When a finger or stylus is pressed on the outer surface, the two layers connect at that point, causing a change in resistance and creating a change in electric current. This change is detected and translated into the X and Y coordinates that accept the input.
These resistive touch screens were great and I am sure they amazed quite a few people, but one thing they really lacked was the multi-touch capability. Enter the capacitive touch screens.
Capacitive touch screens are also coated with Indium Tin Oxide, but only on one layer of glass, with a protective cover layer that constantly holds some electric charge. When you bring your finger close to the screen, the electrostatic field around that point changes, causing a change in capacitance. This change is detected by circuits at each corner of the screen, which then interpret the specific location of the touch.
While this capacitive technology on screens improved sensitivity and visual clarity, the multi-touch functionality only came later with ‘projected capacitive’ technology. This was possible with a grid of micro-fine wires layered over the screen. Each intersection is essentially its own tiny capacitive sensor. Now, when multiple fingers touch the screen, different electrostatic field points can be detected by each sensor, instead of one capacitor for the whole screen. This is what lets you and me pinch, zoom, rotate, and do all kinds of weird things with the screen. So many gestures!
Now, you might have noticed how some screens have so much trouble working with a random stylus. You have to use your fingers on them. Well, those are capacitive screens. While these screens work with a stylus, they need one that is conductive. With a traditional plastic stylus, which is not conductive, you cannot make a change in the electrostatic field and hence, it just won’t work!
Beyond resistive and capacitive touch screens, there are many other types, but I won’t get into those. However, for the lack of touch screen MacBooks from Apple, there is the Force Touch and 3D Touch technology, Apple introduced, first in their Apple Watch in 2014, and later in their other mobile devices.
Force touch works with the use of tiny electrodes around a display’s backlight. These electrodes can measure microscopic changes between the cover glass and the backlight. These microscopic changes happen because of the variation in pressure by a finger. Measuring these changes helps create varied functionality based on how much pressure is being applied — a tap, a press, or a deeper press.
All right. I’ll leave it here for touch screens. Hopefully, you understand these everyday interactions a little better now.
Learn more on this
Want to see a little more on new stuff happening around touch screens? Here you go.
From Foldable Phones to Stretchy Screens
Under-display cameras are slowly getting better
Taking Touchless Interactions To The Next Level With Millimeter Wave
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