This tattoo is temporary, but it’s permanently changed people’s impressions of wearable tech. Meet DuoSkin, an innovation from MIT’s Media Lab and Microsoft Research. The metallic tattoos, inspired by trendy body art, let wearers use their skin as an interface for smartphones and computers. The product isn’t yet available to buy. At this stage, it’s the subject of a paper that will be presented at an upcoming wearables conference. That hasn’t stopped tech and fashion reporters alike from issuing an effusive “Sign me up.”
Yet DuoSkin as more than a story about wearables. These striking tattoos remind us that chemistry underlies the devices in our ever-more-connected world.
Super-thin smart tattoos are not new. Consider cosmetics giant L’Oreal’s patch that monitors exposure to the sun’s UV rays, this temporary tattoo that unlocks your mobile phone and this prototype designed to measure a chemical called lactate, an indicator of fitness and physical performance, in human sweat.
DuoSkin’s innovation is breaking away from the specialized, expensive materials in most skin electronics, such as conductive carbon or silver ink. Cindy Kao, a graduate student at MIT, and her coworkers make the tattoos from everyday materials available at craft stores: temporary tattoo printing paper and gold leaf. Genuine gold leaf is available to buy, but based on the $10-per-pack price quoted in the report, Kao and the team probably used imitation gold leaf, made from a blend that’s mostly copper (Kao confirms they use the imitation leaf.)
Both gold and copper are excellent conductors of electricity. They belong to the “metals” section of the periodic table, where elements have electrons that are free to move about. Electric current, at its most fundamental, is electrons moving along a wire. So it makes sense that elements with less-confined electrons — metals — are going to make better conductors. Budding chemists learn this when they’re still in high school or college, and they’re exposed to several different ideas about how this works at the smaller-than-microscopic level of individual atoms.
Chemistry students learn about other properties of metals that come in handy for these tattoos. Metals are excellent conductors of heat, an important property for the color-changing sensor. Metals are what’s called malleable, meaning they can be hammered into thin sheets (thinness is a desirable quality in a device that’s going to be stuck to the skin). Given all that, it almost feels like using gold leaf for skin electronics should have been obvious. But that’s the funny thing about science. A lot of innovation is only obvious in retrospect. With just one exception in the paper electronics field, the MIT-Microsoft team wasn’t able to find another example of gold leaf used in this way.
Let’s be honest, though. DuoSkin didn’t get massive media attention just because it is cheaper than the competition, or because copper is a good conductor of electricity. Kao’s tattoos are arrestingly beautiful. They are inspired by the metallic temporary tattoos showing up at festivals like Coachella, on Instagram and in street style. DuoSkin tattoos are customizable — volunteers who tried them at MIT were able to design their own tattoos instead of purchasing a one-size-fits-all device. And they are easy to wear – volunteers preferred the gold-leaf tattoos, which can be applied with water, to designs using copper tape, a favorite of the Maker community, as the conductive material.
The DuoSkin tattoos can sense touch input to control a music app on a smartphone, change color based on changes in body temperature, or transmit data to other devices. Remember The Clapper?. DuoSkin is a dazzling–and glam–reminder of progress.
By Carmen Drahl for Forbes