Wearables are great, sure, except you have to wear them. Wouldn’t it be nice if that functionality was printed right onto your skin? Well, even though it’s not for everybody, it sounds like it might soon be a possibility: CMU researchers have created a durable, flexible electronic temporary tattoo that could be used for all kinds of things.
This might sound familiar — we’ve been hearing about electronic tattoos for a while now. But previous methods were slow and limited, essentially painting oneself with conductive ink or attaching a thin conductive film. If the idea is going to take off, it needs to be easily manufactured and simple to apply. That’s what the team hopes they’ve accomplished here.
“We’re reporting a new way of creating electronic tattoos,” said CMU’s Carmel Majidi in a video from the university. “These are circuits that are printed on temporary tattoo film. We print circuits made of silver nanoparticles, and then what we do is we coat those silver nanoparticles with a liquid metal alloy. The liquid metal fuses with the silver to create these conductive wires on the tattoo; the tattoo can easily be transferred to skin, and the conductivity is high enough to support digital circuit functionality.”
The big advance, as co-author Mahmoud Tavakoli explained in a news release, is the ability to join the inkjet-printed nanoparticle patterns with the other metal (a gallium indium alloy) at room temperature.
“This is a breakthrough in the printed electronics area,” he said. “Removing the need for high temperature sintering makes our technique compatible with thin-film and heat sensitive substrates.”
In other words, it can easily be attached to fragile things like temporary tattoo film, cheap and abundant, or perhaps to a bandage. Fortunately the tattoos are also quite flexible, maintaining their functions when deformed, and won’t rub off easily.
The most obvious application is in the medical field, where a tattoo could perhaps replace a finger clip or armband heart monitor, or perhaps include chemical sensors that test blood sugar and alert the user if it gets too low. There are plenty of other ways that a skin-mounted circuit could be applied, but most haven’t been thought up yet. It may be time to brainstorm!
The paper describing the e-tattoo technique was published in the journal Advanced Materials.