Scientists have used nanotechnology to create “selectively wet” materials that can be used to write long-lasting messages with water.
The concept, called "hydroglyphics," was exhibited by scientists at Harvard who recently teamed up with a group of Merrimack, N.H., high school students and faculty to make an educational demo.
The demo, appropriately entitled "Hydroglyphics," helps people visualize the difference between water repelling and wetting surfaces. The main principle behind hydroglyphics (a combination of the words “hydro” and “ hieroglyphics ”) is that by changing the properties of a surface, you can make your own special prints using water. All you need is some foam stickers, a modified Tesla coil and a Petri dish.
Each audience member takes a Petri dish and chooses a favorite sticker, tacking it onto the bottom of the dish. The demo performer then puts each dish under the Tesla coil, and zaps them. A purple spark appears accompanied by a loud noise. Once the sticker is removed, water is added to the dish. The water fills up everywhere except on the area where the sticker had been, creating an “engraving.” The message can last about one month.
Harvard scientist Philseok Kim, the first author on the paper about this demo, stumbled upon the idea for hydroglyphics. While helping one of Merrimack’s teachers, Raymond Sleeper, come up with a new demo, he experimented with equipment in the lab that was being used for other research projects.
“I tested [the demo on] a Petri dish, to see how much contrast between hydrophilicity and hydrophobicity we could make,” Kim, of the Wyss Institute, said. “To our surprise, it nicely generated strikingly good contrast.”
The Petri dishes originally have a plastic structure that repels water (hydrophobic). When treated with the Tesla coil, the air becomes conductive and oxygen combines with the plastic, making the Petri dish surface attracted to water (hydrophilic). However, the area under the sticker was protected from the air, so it still repels water. Water in the dish sticks to the hydrophobic regions, keeping the message area dry.
The hydroglyphics demo has been a success wherever the researchers have taken it, Kim said. “Purple electric arcs with funny zapping noise, cute and colorful stickers, and mystery messages… all of them are a series of 'wow' moments that just happen over a few minutes. I think this is a truly engaging combination.”
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