The Phone in Your Hand

01 / 14Screen Fingerprint Resistant Coating An impossibly thin slippy surface Run your finger across a window. Smooth, but it drags. Now do the same on your phone. Your finger glides.The difference is a non-stick coating one molecule thick, and every time you touch the screen a little of it wears away.Oleophobic FluoropolymerIntroducediPhone 3GS2009Like a non-stick pan, the screen is coated with fluoropolymers, chains of carbon atoms with fluorine attached instead of the usual hydrogen.The carbon-fluorine bond is incredibly stable, giving the coating very low surface energy: oily fingerprints wipe away, and your thumb gets that gliding feel. It also explains why a phone left face-down on the faintest slope will attempt escape. 02 / 14Screen Screen Chemically hardened glass armour The first iPhone Steve Jobs revealed on stage had a plastic screen. In the months before shipping, he found the keys in his pocket had scratched the prototype and he insisted on a last-minute upgrade.The chemically strengthened glass he demanded is seven times stronger than normal glass and quickly became the industry standard.Aluminosilicate GlassIntroducediPhone2007Normal glass, like bottles and windows, is made from silica. Smartphone glass has aluminium woven into the silica network, stiffening the structure and helping it resist cracks.Sodium ions are also added to the mix and sit in the gaps of the silica-alumina grid. The finished sheet is dipped into a 400°C potassium bath. The small sodium ions swap places with large potassium ones, squeezing into the structure, compressing the surface.When an impact occurs, a crack must first push through this compressed layer. 03 / 14Screen Touch Detector An invisible grid that senses your fingers Your finger is tracked by capacitive touch, shown live at the bottom.Older touchscreens were resistive, like on the Nintendo DS. They required a push, often with a stylus, to force two layers together. They could only detect one touch at a time and included a screen-dulling air gap.Capacitive touch made the glass itself a multi-touch sensor, and buttons disappeared to free up more screen.Capacitive touch detectorIntroducedLG Prada2007LG narrowly beat Apple to market, but Apple paired the hardware with the gestures we all still use: flicking to scroll, pinching to zoom, and making pages glide and settle as if they have weight.Conductors have a bunch of free electrons that carry electricity, but they also reflect light. That’s a problem for something in front of a display, but indium tin oxide has a rare trick. It has just enough electrons to conduct without becoming a reflective electron-sea, making it both transparent and conductive.It’s arranged as a whisper-thin grid and holds a tiny electric field. When your finger touches the glass above, it disturbs the field where it lands. A controller chip scans the grid hundreds of times a second, looking for those tiny changes and turning them into coordinates. 04 / 14Screen Display Millions of lights forming everything you see The display you’re reading this on is an absurd grid of exactly 0 tiny, multicoloured light bulbs, known as pixels.Turning them on in a pattern creates the shapes and colours on the screen, with a few hundred forming each of these letters. When you scroll, the text is not really moving. Pixels are lighting and dimming more than a hundred times a second.AMOLED & TFTAMOLEDBenQ-Siemens S882006A classic bar-style phone with an AMOLED display smaller than a passport photo. Eight of them would fit inside the screen you’re reading on now.Every pixel is made of subpixels: microscopic red, green and blue lights, which blend in different amounts to make any colour on your screen. A light bulb needs to be connected to power, so a layer of transparent indium tin oxide carries power across the top, and a metal layer feeds power from below.Left like this, the screen would just glow at full brightness. An expensive, big flat light. So, the subpixels sit on a layer of thin-film transistors: millions of dimmer switches, controlling the brightness of each pixel. Beneath it all, a final slab of glass protects the delicate filling. 05 / 14Senses Vision Front-facing eyes watching you and the light Three tiny eyes look out from the front of your phone. You can see the selfie camera. If you’re older you might remember the workaround: a phone with a tiny mirror-dimple on the back, so you could line up your own face.The other two eyes are hidden. They measure light to automatically adjust the screen brightness, and to stop your cheek from hanging up a call. Try holding your awake phone to your cheek and slide it around, nothing happens.Front Camera & PhotodiodesFront CameraKyocera VP-2101999The first camera phone was front-facing. It could do a kind of stop-motion video call at two images a second, or save up to 20 grainy photos.Proximity SensorNokia 76502002No touchscreen, so the proximity sensor was for switching a call off loudspeaker.The proximity detector and light sensor both use light-sensitive photodiodes, like tiny solar panels. The light sensor reads how bright the room is. The cheek detector sits behind an infrared filter, and an infrared LED shines out. When something is close it detects the light bouncing back.In modern phones these sensors hide under the display, peeking through carefully engineered spots. It’s likely that the selfie camera will go the same way soon too. We’ll come back to cameras when we get to the back of the phone. 06 / 14Senses Navigation A sea captain’s chest of treasured instruments shrunk into your phone In the 18th century, a sea captain measured the angles of the stars and sun to fix his position. GPS has replaced that ritual, but instead of eyeballing the angles, your phone listens to the time from atomic clocks aboard a dozen satellites overhead. The signal always travels at the speed of light, so tiny differences in their arrival time let your phone fix its position.Time is key to both. For the sea captain latitude (how far north or south you are) is easy, he just needed the angle. For longitude he also needed to know the exact time back home.John Harrison, a self-taught English carpenter, spent decades on the problem of keeping time on a pitching, salt-soaked ship. His H4 Marine Chronometer drifted less than a second a week, finally cracking longitude. Accurate clocks spread to every ship, and in busy ports a time ball would drop from a pole at exactly 1pm for all to set the time.Your phone’s clock is worse than his. It drifts about ten seconds a week, but unless in airplane mode it has a time ball of its own in the form of network time.Microelectromechanical SystemsGPSBenefon Esc!1999The captain’s other instruments survive too, shrunk into microelectromechanical systems: intricate working machines no larger than a matchstick head, with moving parts thinner than a human hair.Like computer chips, they’re etched from silicon, carving out microscopic structures that bend, vibrate, and flex in response to the world. The Other InstrumentsCompass IntroducedNokia 6210 Navigator2008 A magnet, if free to move, will spin to align itself with Earth’s magnetic field and point north. The MEMS compass is made from a sliver of metal smaller than a red blood cell. Instead of physically moving, this metal subtly shifts its electrical resistance in response to the Earth's magnetic field. Your phone detects these changes to calculate which way it’s facing; critical in maps, but also useful for screen rotation when you're in odd positions, and as a backup reference for the gyroscope. Barometer IntroducedGalaxy Nexus2011 Above your head is a column of air 30 miles high. This has weight, which we call air pressure. Moving higher means less air stacked on you, so the pressure drops. Weather also plays a role: before a storm, pressure falls, while high pressure usually means clear skies. People once used mercury barometers, elegant glass tubes labelled Fair and Stormy, their needles shifting to warn of changing weather. Your phone contains a MEMS barometer. A delicate, flexible diaphragm inside a microchip bends slightly under changing air pressure. Having a rough idea of your altitude helps to lock onto GPS satellites faster. Clocks IntroducedNEC P31990 There are dozens of clocks scattered across your phone’s circuits, keeping everything in sync. At the heart of these are resonators. Quartz crystals vibrate at a known speed when electrically stimulated, like a microscopic tuning fork. MEMS oscillators take this a step smaller, resonating tiny silicon structures suspended in vacuum. 07 / 14Senses Orientation Tiny suspended structures that know which way is up Released in 2008 for the iPhone, iBeer turned the screen into a pint that you could drink by tilting. It racked up millions of downloads, a simpler time when making a phone respond to movement felt magical.Inertial Measurement UnitIntroducediPhone 42010The trick was powered by the phone’s accelerometer, which detects motion by measuring acceleration. Inside the chip, combs are suspended on microscopic springs. When the phone moves the combs shift, changing the gaps between the teeth. This alters an electrical charge, which the phone measures to track movement. Because gravity is always pulling down, the accelerometer can also tell which way is down.Accelerometers alone are imprecise, which is where the gyroscope comes in. Instead of measuring straight-line movement, the gyroscope detects rotation with a vibrating structure. Moving things don’t want to rotate (the Coriolis effect), so as the phone turns, the mass pushes back a measurable amount.There are three of each, packaged into a single chip. Together they give the phone six senses of motion, letting it rotate the screen, steer games, stabilise cameras, and pour the perfect fake pint. 08 / 14Senses Vibration Vibrating air to be heard, and your hand to be felt