Smallest Fountain Pen

Researchers have developed the world's smallest fountain pen.

"[It is so] tiny it can draw lines a hundred times thinner than a red blood cell.

... [I]t can paint lines as thin as 40 nanometers and has its own reservoir to hold various types of inks, including pigments for painting patterns and organic materials for designing sensors.

...

The new pen can be attached to the atomic-force microscope, which allows scientists to see nanoscale environments as well as draw on them. Possible uses for such a tiny pen, or an array of several of them, include crafting miniscule protein arrays and complex semiconductors.

Because scientists built the pen using standard microfabrication techniques and materials, it will be possible to mass-produce the tips."