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Harry Potter’s disguise of choice isn’t just for stalking the halls of Hogwarts sight unseen. Scientists from Towson University and the University of Maryland have harnessed the power of 25,000 invisibility cloaks to slow down—and even stop—light, producing what is colloquially known as a “trapped rainbow.” A mere 30-micrometers in diameter, each “cape” comprises a micro-lens that bends light around itself, effectively obscuring an area in its center. Laid out uniformly on a 25-millimeter gold sheet, the materials form a first-of-its-kind array, manipulating bands of light through the intervening gaps to create the optical phenomenon.

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Slowed-down light interacts differently with molecules than light traveling at regular speeds, which means that trapped rainbows can help identify biological materials based on how much light they absorb and emit. Applied to biosensors in fluorescence spectroscopy, they can also promote more-detailed analyses.

Trapped rainbows can be used to identify biological materials based on how much light they absorb and emit.

“The benefit of a biochip array is that you have a large number of small sensors, meaning you can perform many tests at once,” says Vera Smolyaninova, lead author of the study, which was presented in the New Journal of Physics on Friday. “For example, you could test for multiple genetic conditions in a person’s DNA in just one go.”

Because it allows researchers to examine fluorescence at thousands of points simultaneously, the technology is the key to making “spectroscopy on a chip” a reality, Smolyaninova adds. No spells, charms, or hexes necessary.

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