Beyond matters of form, the team focused on the function of the multi-touch. Most touch devices at the time used resistive touch screens, based on two thin sheets of conductive material separated by a thin gap of air. When the screen is pressed, the two layers make contact, registering the touch. Resistive screens were typically made of plastic, and were common in pen-based devices like Palm Pilots and Apple’s Newton.
Jony’s design team tried using a resistive screen for the iPhone, but were unsatisfied with the results. Pressing on the screen distorted the picture, and the screen tired the fingers because the user had to press pretty hard. It just didn’t live up to the promise of the name (“touch screen”), which the designers thought should convey the illusion that the user was literally touching the content.
Moving on from the resistive screen, the hardware team set out to build screens based on capacitive touch, registering changes in electrical charges (or capacitance) across its surface. Human skin is electrically conductive, and a capacitive touch screen uses that characteristic to detect even the lightest touch. Apple had been using capacitive touch technology for several years with the iPod scroll wheel, laptop track pads and the Power Mac Cube, which had a capacitive on-off button. But the technology hadn’t been applied to transparent screens. One problem was that there was no supply chain for capacitive screens.
No one was producing them on an industrial scale at the time—but Apple found a small company in Taiwan called TPK that was producing them for point-of-sale displays using an innovative but limited-run technique. Jobs made a handshake deal with the company, promising that Apple would buy every screen the factory could produce. Based on this agreement, TPK invested $100 million to rapidly ramp up their manufacturing capabilities. They ended up supplying about 80 percent of the screens for the first iPhone, growing rapidly to a $3 billion business by 2013.
Excerpted from Page 145 of Jony Ive – The Genius Behind Apple’s Greatness by Leander Kahney