Anirudh Sharma was at a conference in India when he noticed black particles accumulating on his white shirt. The specks settling on him were from pollution in the surrounding air.

Byproducts from burning fossil fuels such as gasoline and coal are causing health problems and climate effects around the world, especially in India's growing cities. In that moment a few years ago, though, Sharma saw the pollution particles as something simpler: A coloring agent.

He went back to MIT Media Lab in Cambridge, Massachusetts, where he was a graduate student focused on augmented reality, and began working on an idea to turn carbon pollution into ink. Using candle soot to start, he came up with a prototype. After finishing his master's degree,