Hitting “print” is easy. Getting a perfect printout is not. All too often, inkjet printers spew out smudged or smeared pages. Now, a new study of the physics of ink concludes that the culprit is the gloopiest ink.
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Inkjet printers have a tiny nozzle, or inkjet, that squirts droplets of ink onto the paper as it passes through. Ideally, the ink forms into a perfect round droplet as it launches from the inkjet, hitting the paper right on target. But droplet formation is affected by ink properties including density, surface tension and viscosity, which is the measure of resistance to flow or “gloopiness.” And if the droplets aren’t just right, a splotch appears instead of a crisp line of text, the researchers say.
Scientists use a ratio called the Z number to describe the surface tension and viscosity of a particular ink. Inks with lower Z are more viscous, while inks with higher Z have more surface tension, explains material scientist and study coauthor Jooho Moon of Yonsei University in Seoul, Korea.