The inks were produced at Missouri's Washington University in St. Louis, by a team led by Assoc. Prof. Chuan Wang and graduate student Junyi Zhao. Previously, the scientists had developed inks that could be used to produce stretchable LEDs via an inkjet printer.

Adapting those inks for use in ballpoint pens involved adjusting their wettability (a liquid's ability to maintain contact with a solid surface) and improving their writability. The researchers also had to boost their ability to be applied to porous or fibrous surfaces – like paper or fabric – without running or mixing with one another.

So, just how do the inks work?