"Temporary tattoos aren't just for style anymore," said Aneri Pattani at The New York Times. Japanese scientists have developed a wearable sensor that can monitor patients' vital signs, and also "looks and feels like a henna tattoo." That's a big advantage over current devices made out of polyester or rubber sheets that aren't breathable enough to allow air to pass through, making the wearer sweaty and itchy.
The prototype sensor is constructed from nanoscale mesh, "a spaghetti-like entanglement of fibers a thousand times thinner than a human hair," and can be applied in the same way as a temporary tattoo. The sensor can be rubbed off in water, "so in reality, it will need to be replaced after every shower or bath," but researchers hope that problem will be solved with future research.