While experimenting with a polymer material known as PEDOT, Princeton University researcher Sven Moller determined that although the plastic conducts electricity at low voltages, it permanently loses its conductivity when exposed to higher voltages. Together with colleagues from Hewlett-Packard Laboratories, he developed a method to take advantage of this property to store digital information, which can be stored as collections of ones and zeros. The PEDOT-based memory card consists of a grid of circuits comprising polymer fuses. A large applied current causes specific fuses to "blow," leaving a mix of functioning and nonfunctioning connections. When a lower current is later used to read the data, a blown fuse blocks current flow and is read as a zero, whereas a working fuse is interpreted as a one. Because the storage method involves a physical change to the device, it is a so-called WORM--write once, read many times--technology. "The device could probably be made cheaply enough that one-time use would be the best way to go," says study co-author Stephen Forrest of Princeton University.
The team predicts that one million bits of information could fit into a square millimeter of material the thickness of a sheet of paper. A block just a cubic centimeter in size could contain as many as 1,000 high-quality digital images, the scientists suggest, and producing it wouldn't require high-temperatures or vacuum chambers. In addition, unlike a CD, reading data stored on this memory block does not involve any moving parts or a laser. Instead it can be plugged directly into a circuit. Testing to determine compatibility with existing electronic hardware and developing large-scale manufacturing techniques could take around five years, Forrest notes. "This is just the first step," he says, "although it's a core step."