For decades, electronic devices have been getting smaller, and smaller, and smaller. It's now possible—even routine—to place millions of transistors on a single silicon chip.
But transistors based on semiconductors can only get so small. "At the rate the current technology is progressing, in 10 or 20 years, they won't be able to get any smaller," said physicist Yoke Khin Yap of Michigan Technological University. "Also, semiconductors have another disadvantage: they waste a lot of energy in the form of heat."