Ink is so permanent. In many cases, that is the ideal. But there are instances where permanence is not just uneconomical but also inefficient. While digital displays or even e-ink can address some of those, they are at times too volatile and always more expensive. Enter HP IonTouch, a new kind of printing technology that bridges the gap between permanent ink and modifiable displays. And it is so cheap and so small that it takes only a few cents to make a display no larger than a credit card.