I love the beach. What I don鈥檛 love is when I try to use my phone after taking a dip. One droplet of water hits my phone and somehow opens an app I didn鈥檛 know I had. Unfortunately for me, this is not an experience isolated from the beach. Whether it's sweat dripping on my phone while I鈥檓 uploading a run to my Strava, or answering a text fresh out of the shower, the water always seems to make my phone do the opposite of what I want it to do.
Until about one week ago, I accepted this occurrence as just a fact of life. Not anymore. When I thought about why water made my phone go haywire, I realized another unfortunate truth... I didn鈥檛 know how phone screens worked in the first place. As such, this article will be a gift from me to you, an imparting of newfound wisdom.
A Blast in the Past
Before I get into the nitty-gritty of touchscreen technology, let鈥檚 bring it all the way back to the beginning: the physical phone screen. The birth of the phone screen was actually the result of an in chemist, Dr. Donald Stookey鈥檚 laboratory. In 1952, the young chemist found himself researching the properties of glass. One day on the job, instead of heating a glass plate to 600潞C, he heated it up to nearly 900潞C! Expecting to open the oven to a molten pile of mush, Sookey found an opaque, white plate that was extremely durable and shatter-proof. This finding gave rise to CorningWare, or what is better known as . (Basically, just ceramic cooking ware that is resistant to thermal shock). This material proved to be so successful for the Corning Glass Works Company that they carried out a large-scale research project to make ordinary, transparent glass as strong as these glass-ceramic products. By 1962, they had done it. In the project called 鈥淧roject Muscle,鈥� Corning developed an extremely durable chemically strengthened glass. It was only in 2006, following Corning鈥檚 tradition of making strong and damage-resistant glass, that they developed a product that made its way to almost every smart phone screen. It was given the name: Gorilla Glass.
The science behind the glass鈥檚 strength is quite fascinating. starts with a special type of glass that is composed of aluminum, silicon, and oxygen 鈥� called aluminosilicate sheet glass 鈥� and traces of sodium ions. This glass, while still strong, isn鈥檛 much to write home about. The real magic begins in the second stage. The glass is immersed in a molten potassium salt solution which is about 400潞C. In this bath, the small sodium ions present in the submerged glass are replaced by larger potassium ions from the bath. Due to the high temperature of the bath, the ions in the glass become mobile, enabling the exchange: sodium ions migrate out into the bath which the potassium ions take their place in the glass. Because the potassium ions are larger, they occupy a greater volume than the sodium ions did. This tight packing results in compression of the glass, increasing the glass鈥檚 strength and resistance to damage.
A Tale of Two Screens
Now that you are experts on the chemistry of our smart-phone screens, it鈥檚 time to understand how we get these touchscreens to work. In brief, a is a type of display screen that responds to touch input from the user. There is much more to your phone than Gorilla Glass, even if that is all you can see. That seems like a transferable metaphor...
While many touch screen technologies exist, the most relevant to our story are resistive touchscreens and capacitive touchscreens. Simply put, resistive touchscreens use pressure to detect our touch whereas capacitive touchscreens use electrical charges to do so.
Resistive touchscreens consist of two thin layers: one made of conductive material and the other made of resistive material. These two layers are separated by tiny spacers. When you press on the screen, these two layers touch, closing the electrical circuit. This contact changes the current flow of electricity, and the system software recognizes that there has been a change in the current at that specific point. The system will then carry out the action that corresponds to that spot.
Let鈥檚 look at an example. First let鈥檚 find a resistive screen. If you fancy yourself a self-checkout person at the grocery store (like me), the screens that you interact with use resistive touchscreen technology. Our example lies in the pre-payment section of self-checkout. After scanning your items, it is time to click the green 鈥淧ay鈥� button on the screen. When you press 鈥淧ay,鈥� the two thin layers under the glass touch, completing the electric circuit. The system then detects this change at the 鈥淧ay鈥� button and knows that it is being prompted to bring you to the next screen: selecting payment type. That鈥檚 it! Because a selection on the screen is solely dependent on where you place pressure, you can use a finger, a pencil, a glove, or pretty much any object capable of producing enough pressure.
Capacitive screens are a bit more complex. Under the Gorilla Glass, or another type of extra-durable glass, these screens contain a layer of copper or tin oxide that stores electric charge. When you touch a capacitive screen, a very small electrical charge is then transferred to your finger. Don鈥檛 worry! It is harmless. When the electrical charge is transferred to your finger, there is a small voltage drop in the place where you have touched. Like in resistive screens, the software then recognizes where this voltage drop point occurs and carries out the desired action.
Have you ever gotten incredibly frustrated at your phone when you have tried to type wearing gloves? This winter ire never goes away for me. The reason we are unable to use regular old gloves on capacitive touchscreens (therefore our phones) is because the gloves cannot conduct electricity. This is why many gloves now have different colored tips on the pointer finger and thumbs, because these tips are sewn with a conductive thread! Now that鈥檚 a fun fact that is sure to impress. This technology is also responsible for my aforementioned sweat/beach frustration! Because water is a great conductor of electricity, when it goes on your phone screen, it is effectively making many selections at once 鈥� sending the system into overdrive, hence your phone taking on a mind of its own, or, rather, the mind of the water!
While most smartphones continue to use capacitive screens, the technology is evolving at a rapid pace. Next time someone complains about their touchscreen, you might be able to offer a helpful fact... or maybe you can take the opportunity to show off! Either way, hopefully I delivered on my promise to impart some difficult wisdom.
Eva Kellner is a recent graduate from the Faculty of Arts and Science, with a major in Environment. Her research interests include urban green spaces, urban agriculture, and outdoor community spaces - all as promoters of climate resilience among city-dwellers.
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