To keep the surface of our eyeballs moist, our eyelids spread a film of oil that prevents a thin layer of tears from evaporating. Recognizing that the same principle could be used to keep ink from drying out in the print nozzle opening, the researchers developed a system that uses a droplet of oil to block air from getting to the ink in the nozzle and drying it out.

Because mechanical shutters like eyelids would not work at the small scale of the inkjet nozzle, as the droplet would stay in place thanks to surface tension, the system uses an electric field to move the droplet of oil in and out of place. The technology could be adapted for use in other devices in which the material being sprayed through the nozzle is even more valuable and expensive than ink - hard as that may be to believe, such substances do exist, according to the researchers.