The two began a project in the mid-2000s developing liquid-resistant surfaces for the Air Force, which wanted to make materials like O-rings resistant to liquids like jet fuel. Jet fuel, McKinely explains, is a liquid with low surface tension, which means, in very simple terms, that it forms droplets easily.

Liquids like fingerprint oil and sweat, as it happens, also have low surface tension, because theyre both full of bodily secretions like lipids and fatty acids, McKinley says. This is why they are so hard to remove, he says. They want to spread over everything.

The suggestion that McKinleys and Cohens surface treatment might repel finger oil and sweat caught the attention of the computer industry. After we released a couple of research papers in 2007 and 2008 describing our results, we immediately began getting calls from technology companies, McKinley explains. Some in the tech industry saw in the research a possible opportunity to make smudge-resistant touchscreens.

McKinley and Cohen are developing techniques for texturing surfaces with nanofabricated structures that form a forest of microscopic structures that look like tiny round platforms held up from below by thin pedestals. The structures are only about 200 nanometers in size; this is smaller than the wavelength of light, making them potentially transparent, McKinley says.

Theoretically, the tiny nail-shaped structures could be spaced at just far enough apart to prevent the liquid and oil droplets resting on top from combining with other droplets and spreading out. This coalescence and spreading out into a thin oily film is what causes surface smudging and smearing.