Flexible electronics have been a hot topic in research for years, and scientists have made real progress in transforming parts of those bulky motherboards in your laptop into impossibly thin, gold leaf wiring that can go on your skin like a temporary tattoo. But look a bit deeper into most of these projects, and you learn there’s a pretty big catch: Yes, the wires themselves are flexible. But somewhere, there’s still a blocky processor full of inflexible transistors—the on/off switches that power calculations in computers—that’s made the same way they’ve always been made. And that’s a big problem, especially when it comes to the promise of wearables in medicine; internal medical devices need to flex and squish with your soft tissue.
A new breakthrough out of Tufts University, just published in ACS Applied Materials and Interfaces, could fast-forward us into a new era of wearable electronics that are woven like clothing, and even might be sewn into our skin and organs to track our health.
The scientists developed a transistor out of linen thread. That means the thread can transfer electricity like an insulated wire, be turned on and off instantaneously like a processor, and connect a network of sensors on or inside your body.
“Some of the flexible electronics are basically, they just take the same hard electronics and try to pin them down—they place them on a flexible polymer and they call it flexible elections,” says Sameer Sonkusale, the principal director at the Nano Lab at Tufts who led the research. “It’s a great idea! And it does work. We were looking at it from a different angle, to make things inherently flexible. It took a while for us to realize that threads are extremely flexible substrates, so why don’t we make circuits on them?”
The thread itself is dipped into a vat of gel, which coats the linen with a thin layer of carbon nanotubes—the wonder material known for all sorts of amazing properties, from enhanced conductivity to durability. Sonkusale stresses that this production process is very simple and scalable by design, because the more complex and difficult aspect of the process is the chemistry his lab has already developed. To create the nanotube thread in a factory only requires a quick dip, just like it’s being dyed. In fact, Sonkusale says that you could actually dye the thread and add nanotubes in the same step. That means traditional textile manufactures should have little problem producing electronic linen.
Once created, the thread can still be handled as normal thread. “You can literally take a sewing needle or use any process to stitch the transistor on anything you want,” says Sonkusale. “You can transdermally suture it into the skin itself. These are transistors that can go anywhere.”
Given that modern microprocessors contain billions of transistors, Sonkusale doesn’t imagine a garment—even with tens of thousands of transistors—ever coming close to matching the processing power inside your smartphone or laptop. “The idea here is not to compete with silicon electronics. We’re not trying to make another microprocessor on a thread,” he says. “But there are applications in biomedical when putting a hard silicon chip inside the body is not practical. It’s not compatible. You have to look at technologies that can cohabitate with your tissues.”
Sonkusale calls the use cases for his linen transistors “processing on the edge.” You could weave a network in someone’s clothing, or inside their body, connecting dozens of sensors, coordinating efficient power control, and pre-managing data very close to the source. It can also amplify the signal of the sensor. In a practical sense, this entire network of switches could be like a little internet in your body, all reachable through a single thread through your skin rather than thousands of wires poking out.
Right now, Sonkusale’s lab is already researching how the thread can be worked into wearables, like a smart bandage that could monitor the progress of a wound in real time. Soon, he’d like to begin testing the technology on animal tissue, to see how bodies react to the material. He suspects the chemistry will need to be tuned to minimize inflammation, and a big question will be how well the linen itself holds up inside tissue. But optimistically, and with funding that he’s yet to secure, he imagines that human testing could begin within two to five years.
“There is very little argument [needed] to be made that, if you figure out the chemistry, this might work out better in skin and tissue than any other thing we’re trying today,” says Sonkusale. In the meantime, private companies can license the technology from Sonkusale’s lab to develop flexible wearable electronics on their own.
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