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Materials

Chemistry In Pictures

Chemistry in Pictures: Janus balls

by Craig Bettenhausen
November 19, 2020
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Most Popular in Materials

A chameleon pattern shows of color-changing little balls.
Credit: ACS Nano/Shin-Hyun Kim
Small spheres are half one color half another.
Credit: ACS Nano/Shin-Hyun Kim

Counterfeiting is an arms race. Governments look for tricky printing techniques, and criminals look for ways to replicate them. A group from the Korea Advanced Institute of Science and Technology thinks their Janus balls, named after the two-faced Roman god of comings and goings, would be hard for ne’er-do-wells to pull off. They used microfluidics to create tiny magnetic spheres that are colorful on one side and black on the other. Normally, density controls the color, with the heavier side of the spheres facing down. But a magnetic field makes them flip, changing the color.

Read more in ACS Nano (2020, DOI: 10.1021/acsnano.0c06672)

Credit: ACS Nano/Shin-Hyun Kim

Do science. Take pictures. Win money. Enter our photo contest here.

Click here to see more Chemistry in Pictures.

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2024 American Chemical Society

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