Ballpoint Pens Let You Draw Custom LEDs

Researchers from Washington University in St. Louis and Florida State University have made a ballpoint pen that allows you to draw custom LEDs or photodetectors on a range of surfaces, by hand.

The ink inside is where the magic happens. Filled with what the team describes as as PEDOT:PSS/PEO composite ink, drawings made with the pen can be lit through the application of electricity — creating what they call PeLEDs in the shape of your choosing.

The composite ink-loaded pens are usable by anyone, without prior training, the researchers claim, and can also be used to draw custom photodetectors — taking advantage of an LED's ability to work in reverse and detect light rather than emit it.