Invisibility cloaks aren't just for Harry Potter anymore. Last year, researchers made one that cloaked things in time. Now they've made thousands of tiny invisibility cloaks that trap a rainbow. That's right, 25,000 invisibility cloaks trapping a rainbow.
The first question you might be asking is: why? Why does it take 25,000 invisibility cloaks to trap a rainbow? Or maybe, why trap a rainbow in the first place?
Well, turns out trapped rainbows can be pretty useful. "The trapped rainbow could be utilised in tiny biosensors to identify biological materials based on the amount of light they absorb and then subsequently emit, which is known as fluorescence spectroscopy. Slowed-down light has a stronger interaction with molecules than light travelling at normal speeds, so it enables a more detailed analysis," the press release says.
And why are there 25,000 of them? They're all laid out on a gold sheet - and since the cloaks are only 30 micrometers in diameter, there need to be a lot of them to cover the sheet. ""The benefit of a biochip array is that you have a large number of small sensors, meaning you can perform many tests at once. For example, you could test for multiple genetic conditions in a person's DNA in just one go," Dr Vera Smolyanivoa, the lead author, said in the press release.
There are other bonuses to the sheet construction. By spreading them out, scientists are creating an array of cloaks that could be used to test cloak performance when they might be positioned close to one another. So if you ever needed to have two invisibility cloaks near each other, it's possible that they could get in the way of each other. The array helps test that. "In this study, for example, the cloaks worked very well when light was shone along the rows; however, when it was shone at different angles, imperfections were clearly visible," the press release writes.
Of course, no one is going to get a gold sheeted Harry Potter cloak any time soon. But micrometer by micrometer we're getting closer to making things really disappear.