Stanford researcher Yi Cui looked across the field of transparent electronics and saw that all was not equal. While all other major electronics components--things like transistors, displays, and other circuitry--have been made transparent, no one had taken the time and effort to create a transparent power source. And you can’t have a fully transparent device without a transparent battery. So Cui made one.
There are a few ways to make an electronic component transparent. One is to make it so thin that it doesn’t register with the human eye. Or you can make the component take the form of a pattern whose features are so small they are invisible. Some battery components are easy to render transparent by shrinking them, but electrodes are particularly difficult to make thin. A super-thin electrode isn’t energy dense, and therefore it doesn’t store up enough power to be useful in any realistic way.So Cui opted for the second approach. He and his team figured that if you can pattern the electrode into a superfine mesh, you can still build an energy dense battery. With enough electrode material distributed across the mesh, a battery can still hold a significant charge.