Wearable electronics are leaving the lab and hitting the runway
From smart phones to FitBits, mobile electronics have been woven into the very fabric of our lives. But things are about to get a lot more literal as e-devices begin to be incorporated into the clothing we wear.
Imagine a “smart” shirt or other item of clothing that can monitor your biometrics and ping your doctor when something is out of the ordinary. Or, to manage diabetes, we’ll use a contact lens or pair of glasses to monitor blood glucose levels—and leave behind forever the expensive and annoying finger prick test kit. But wearable electronics are not limited to health care: A truck driver might wear a baseball cap that monitors her alertness levels.
Rahul Panat, an associate professor of engineering in Washington State University’s Voiland College since 2014, observes that it is consumers who are driving the move towards wearables.
“Consumer tastes started to shift in the late 2000s,” he says. “People are no longer concerned about the speed of microprocessors. Rather, they started paying a lot more attention to function, size, and the coolness of software and devices. That put a lot of new challenges on materials engineers and computer scientists.”
Whatever the application, wearables have a couple major hurdles to clear before they can well and truly be incorporated into our everyday lives.
One, they need circuitry that can bend and flex as vigorously as the clothes we wear. And two, these devices need power supplies that are both tiny and flexible. Therein lie the challenges for materials engineers.
Conductive metals are required to create any sort of power-consuming device. To get smart devices into our clothing where they can do us the most good requires flexible, bendable interconnects that move current from point A to B. And we need batteries that won’t fail when stretched or bent.
Panat says that the current options are either too expensive or too bulky. Gold, while ductile enough to flex in wearable applications, is too expensive. “If someone finds a huge vein of gold on an asteroid, then maybe we can use it in everyday applications,” he says.
Another route to get some flex in metal interconnects is a serpentine arrangement that allows the circuit to straighten without breaking when stretched. But that, Panat says, takes up a lot of real estate. “And the increased length of the conductor increases resistance.” Increased resistance means higher power consumption and more heat, both undesirable with wearable devices.
Panat and fellow Voiland College professor Indranath Dutta, along with graduate student Yeasir Arafat, recently demonstrated a significant advance by showing that the metal indium, deposited as a thin film on a polymer substrate, can be stretched to twice its length without breaking—“a quantum improvement,” Panat says, over current methods.
As part of a team at Arizona State University, Panat had shown that batteries designed with origami creases can fold, bend, and twist. Employing the Miura-Ori pattern of origami folding and using standard materials, the team wrote in Nature Communications that their “strategy … represents the fusion of the art of origami, materials science, and functional energy storage devices, and could provide a paradigm shift for architecture and design of flexible and curvilinear electronics with exceptional mechanical characteristics and functionalities.”
The combination of deformable batteries and stretchable metal conductors opens the door to a wide array of wearable devices. You’ll know you’ve stepped through that door when you put on a nightcap that enables you to sleep better or a smart bike helmet to guide your ride with heads-up GPS and proximity alerts.
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