Circuits on cellulose

You wake up with a heavy head. Was it the half dozen glasses of champagne last night or are you getting sick? In your bathroom is a little strip of paper that can tell you for sure. You place it on your tongue and after a few seconds, you pull it back to see the bad news: There's a small green dot next to the word "flu." When you fish your doctor's business card out of your wallet, you notice it looks different from the last time you looked at it. The phone number for his office was originally black. Now it's displayed in blinking red letters, a sign that the number was changed recently. The electronics in this scenario are not far off; in fact the basic technological breakthroughs needed to make them work have all been achieved in the past few years. At the moment the costs are still too high for them to be used in things like business cards or package labels, but remarkable advances in materials science and simpler fabrication methods are setting the stage for a whole new breed of cheap, bendable, disposable, and perhaps even recyclable electronics. And some of the most exciting work in this field is happening with paper.