Paper Battery
A dip in nanotube ink turns office paper into an electrode

Source: “Highly conductive paper for energy-storage devices”
Yi Cui et al.
Proceedings of the National Academy of Sciences 106: 21490-21494

Results: Office paper dipped in carbon-nanotube ink becomes a strong, flexible, highly conductive material that can be incorporated into lightweight batteries (where it serves as a conductive layer) or high-energy capacitors called ultracapacitors (where it serves as an electrode). Used in ultracapacitors, the material stored more energy than previous electrode materials.

Why it matters: It’s already possible to print lightweight circuits and screens for electronics like e-readers, but conventional batteries still weigh them down. Carbon nanotubes are a promising material because they are strong, conductive, and light, and they can store a large amount of energy–a quality that helps portable electronics run longer between charges.

Methods: Researchers made the ink by mixing carbon nanotubes in water with a surfactant, a chemical that keeps them from clumping together. Paper dipped in this ink soaks up nanotubes like a sponge. After the paper dried, the researchers confirmed the resilience of the material by scratching and rolling it. Then they tested its performance in energy storage devices.

Next steps: The researchers will try to improve the performance of the devices by changing the formulation of the ink.