Twenty years ago, the Pentagon asked George M. Whitesides, a chemist at Harvard University, to invent a way to quickly detect anthrax and other biohazards in the field. His solution was a handheld device that used polymers to draw samples through a complex series of very small chemical baths. If biohazards were present, the chemicals would react. The device worked, but Whitesides was more excited about its civilian potential. Nearly a billion people live without access to hospitals or any reasonably sophisticated means of diagnosing illness; if he could transform the biohazard detector into a universal diagnostic tool, he could help save millions of lives. The design was straightforward. The only problem was that the Pentagon version was too expensive. For years, he and other researchers tried shrinking parts or using cheaper components. Then, four years ago, Whitesides had another idea. What if the whole thing was made out of paper?
Using an $800 printer, he selectively patterned sheets of paper with melted wax to create assay zones, similar to the circuits on a computer chip. He then added assay reagents that changed color when exposed to certain chemicals. The paper would wick blood samples into the appropriate assay zones, where it would bind to the reagents and change color to deliver a diagnosis. Mass-produced, his stamp could cost less than a penny.