Circuits drawn with the pen make LEDs light up and give a 3D antenna its juice.
Gel pens, beloved by middle-school girls, are good for decorating cootie catchers
, evading laboratory ink analysis
, and not much else. But if you replace that metallic ink with real silver, you get something quite remarkable: a pen that can draw functioning circuits on paper. Engineers at the University of Illinois have built such a device
and used it to put together several clever electronic doodads. Silver is a conductor
, so it ferries electrons from a power source, like a battery, to an outlet, like an LED light, even when it's just a line on a piece of paper instead of a wire. Once the silver ink dries, it's as good as wire or printed circuits at conducting electricity, and it survives all kinds of mangling---researchers had to bed the paper back ...
