Scientists have created "electronic foils" that will allow circuits to conform to any surface — or get stretched, bent, and crumpled. The electronics may someday become as common as plastic wrap, researchers say.
In recent years, we've seen a number of breakthroughs in softer, flexible electronics. Much of the work is spearheaded by the uber-productive John Rogers, a materials scientist at the University of Illinois at Urbana-Champaign. A few months ago, Rogers and his colleagues developed stretchy, bendable batteries to power a new generation of flexible displays, solar panels and other devices.
Before that, Rogers helped create the "epidermal electronic system" — a type of small, pliable electronic circuit that can be applied to the skin in a similar manner as the application of a temporary tattoo — and transient electronics that dissolve in the body.
"Rogers' work is really great," says Martin Kaltenbrunner, an engineer at the University of Tokyo. But to expand the applications of flexible electronics even more, Kaltenbrunner and his colleagues decided to design bendy circuits that can be cheaply fabricated over a large area. The electronics, the researchers reasoned, would also have to be super thin. "You cannot really wrap current flexible electronics around anything, but if they were really thin, they could even go into the wrinkles of your skin."
Enter electronic foils.
Using processes common in the semiconductor industry, such as vacuum evaporation and chemical vapor deposition, the scientists manufactured integrated organic circuits onto ultrathin (1 micron) plastic films, also known as polymer foils. As explained in the video below, the electronic foils are just 2 microns thick (one-fifth the thickness of kitchen plastic wrap), 30 times lighter than office paper and have a bend radius of 5 microns, allowing it to be crumpled without harming the circuits. Moreover, given that the plastic films come in huge rolls, the electronic foils can be fabricated cheaply on a large scale.
In their paper, published today in the journal Nature, Kaltenbrunner and his team demonstrated a number of uses for their virtually unbreakable circuits. For example, the researchers built a thin transistor, which they then integrated into a tactile sensor that can conform to uneven surfaces, such as the roof of a person's mouth.
"If you imagine a person that cannot communicate with anything but their tongue, this would be a nice interface," Kaltenbrunner tells io9. "They could give yes or no answers by touching different spots of the sensor, and the device can conform so nicely that it wouldn't be painful to wear." Another use for such a sensor would be as artificial skin for robots, which would give them touch sensitivity.
The team also built a mini temperature sensor that can adhere to a person's finger (or any other skin location). The researchers think that in the future, the simple temperature sensor could be implemented into an imperceptible adhesive bandage for health monitoring.
And when the electric foils are sandwiched between elastomers (rubber), the circuits become stretchable and able to withstand a huge amount of strain. "By doing this you can protect the device from mechanical forces and also reduce strain on the device when you bend it around," Kaltenbrunner says.
In an email to io9, Rogers says the new development is related to his team's previous work, but the organic semiconductors that make up the circuits offer some advantages, such as low-cost, large-area fabrication. He adds:
The diversity of device examples — from transistors, sensors and circuits to integrated systems — and the unusual properties — featherweight construction and rubberband-like stretchability — are quite remarkable.
These and other recent advances in unusual electronic materials are reshaping the way that we think about interfaces between biological systems and semiconductor technologies. The potential implications for health/wellness monitoring and clinical healthcare are profound.
The healthcare field will no doubt benefit much from the circuits, but Kaltenbrunner sees its applications in a much more general, futuristic light. "I really like the idea of making thin-film plastic electronics that you can place on everything," he says. "We are getting really close to what I've seen in sci-fi movies, where you just touch a surface and it does something."
You can check out the abstract of the paper in Nature.
Images and video via Someya-Sekitani Group, The University of Tokyo.