Image: John Rogers
There have been a few things holding back the wide implementation of skin-thin e-tattoos: It’s hard to power them, it’s hard to store data, and they’re expensive to make, as nanomaterials don’t come cheap. So a team of researchers just said to hell with it and made one that uses off-the-shelf, mass produced chips and components—turns out it works just as well as anything we’ve seen before.
The idea seems too simple. If you’ve ever had a look inside your smartphone, you’ll realize how absurdly small the components have become. But sticking a bunch of chips on your body, band-aid style, isn’t exactly comfortable because the chipsets aren’t very stretchy. An e-tattoo is no good if the wires snap all the time.
John Rogers of the University of Illinois Urbana-Champaign (who is often at the forefront of this kind of thing) has found a way to solve both of those problems.
“What we attempted to do was to come up with a concept and approach that’ll let us use off the shelf components that can yield an overall system that is matched to the skin but embedded with commercial, conventional devices,” Rogers told me. “To do that, we looked at two simple but powerful ideas. The concept of microfluidics and wiring that’s fabricated using a pre-folded-up geometry.”
Put more simply, Rogers lubricated the chips and put a “pillow” of fluid both below and above the electronic components, then wired them together using an origami-like pattern. The result is an e-tattoo that’s comfortable, stretchable, and powerful.
“Everything is done for comfort—if you put a blindfold on and put it on, you wouldn’t know there’s chips in there,” he said. “Then these almost serpentine wires that loop back on themselves, when it’s stretched, the network unfolds.”
In a paper published in Science, Rogers reports that his e-tattoo is just as good as an EKG machine at monitoring a heartbeat. Because he’s not using proprietary technology, the tattoos can easily be outfitted with wireless internet access, bluetooth, accelerometers, and near field power coupling for wireless charging. By thinking simpler, he’s done something that he and others have been trying to accomplish with nanotechnology with components that already exist.
“It’s a generic set of ideas applicable across a whole range of sensor types that are already well developed, sensitive, and accurate,” he said. “These aren’t a curiosity; you can build real things that offer clinical usefulness that are far beyond what you can do with a Fitbit.”
The development has exciting potential in both healthcare and techy sectors—who wants to clip on a Fitbit when you can simply slap one on your arm or leg and forget about it? And, because most of the components are already made, this technology can probably be mass produced and sold at a reasonable price point.
“That’s our hope and belief,” he said. “I’m optimistic that over the next year and a half you’ll start to see this scaled up.”
To do that, Rogers has formed a small company that’s handling those sorts of questions, while he gets back to nanotechnology. Making e-tattoos thinner, more comfortable, and more powerful is always going to be the goal, and nanotechnology is ultimately the way to do that, but in the meantime, this isn’t a bad alternative.
“I think ultimately, the two streams of thought are going to be complimentary—one doesn’t replace the other,” he said. “But certain classes of batteries and capacitors may never be available in the ultra-thin geometry. The kind of idea we just put forward enable modes of function that are difficult or impossible to achieve [with nanotechnology today].”
Of course, there’s still one problem: There is a limit to how far you can stretch the patch and it will eventually break if you pull too hard. Rogers is currently working on making the tattoos more durable. In the meantime, they should do just fine if you don’t yank on them too much.