As such, Morteza (Mory) Gharib (PhD '83), the Hans W. Liepmann Professor of Aeronautics and Bioinspired Engineering at Caltech, says he was surprised when he and his team were able to generate a stable ring of plasma in open air using just a stream of water and a crystal plate. Their findings will be published in the Proceedings of the National Academy of Sciences the week of November 13. "We were told by some colleagues this wasn't even possible. But we can create a stable ring and maintain it for as long as we want, no vacuum or magnetic field or anything," says co-author Francisco Pereira of the Marine Technology Research Institute in Italy, a visiting scholar at Caltech. (View Highlight)
When the jet hits the crystal, the water creates a smooth, laminar flow of positively charged ions across the negatively charged surface. At the shear region, where the stream strikes the surface and flows outward across it, the triboelectric effect triggers a high flow of electrons through the water to its surface. This flow of electrons ionizes the atoms and molecules in the surrounding gas near the surface of the water, creating a donut, or torus, of glowing plasma that is dozens of microns in diameter and visible under a microscope. (View Highlight)
Gharib and his team fired the water jet at surfaces of different textures and found that the smoother the surface, the clearer the structure of the plasma ring. The ring is stable, and as long as the water continues to flow, the ring maintains its shape and size. (View Highlight)