Each fluid reveals a different letter.

What’s the News: Scientists have developed a chip that can instantaneously identify fluids applied to it, just from their unique surface tension. In a handheld device, it could help toxic site remediators figure out what that ominous clear liquid is. And there’s a bonus for the kids-in-the-treehouse user demographic: different secret messages can appear on the chip depending on what fluid is applied.

What’s the Context:

Materials scientists—who, put simply, study stuff—have long been interested in how fluid moves through the tiny myriad holes of substances like coral, or bone.
By building coral-like structures out of glass in the lab and then treating them with various chemicals, they can make it impossible for some fluids to seep into the maze of holes, while others glide right in. A substance’s ability to absorb fluids is called “wettability,” and it’s the subject of much research, as you can imagine—it’s the reason your raincoat stays dry and your sponge sops up spilled juice.
A fluid’s ability to seep through holes is dependent on its own physics, as well as the wettability of the substance. Molasses, for instance, is too thick to creep into holes ...