You may soon be able to control your music's volume or change the TV channel simply by swiping on your forearm after the invention of a temporary tattoo that can be used to control a mobile phone.Researchers at the Massachusetts Institute of Technology and Microsoft have demonstrated technology that affixes gold leaf patterns to skin, creating a circuit.The inexpensive material would be able to respond to touch, allowing wearers to swipe to control the phone.While it is not the first time ways to create on-skin interfaces have been developed, the researchers said their "DuoSkin" system was cheaper and more comfortablethan other inventions.The gold-leaf circuit connects to a small chip which is able to wirelessly beam a Bluetooth signal to a device, in the same way a smart watch or remote control does. The researchers demonstrated that the tattoos could also respond to the body's temperature, lighting up or changing colour when the skin heats up.They could also contain a small NFC chip, allowing users to tap a phone on to the skin to read information or activate a feature.The invention taps into a growing trend for temporary metallic tattoos as a fashion statement.Cindy Hsin-Liu Kao, a PhD student at MIT, said people will soon be able to walk into tattoo parlours and have a connected tattoo fitted on to their skin...