Wearable medical devices offer patients and healthcare providers significant promise in terms of quality of life by improving data collection while allowing for greater patient mobility.
But developing useful wearables for use on skin can present challenges: the devices should be flexible enough to move with the user while retaining performance, and they must be cost-effective to manufacture. Flexible printed circuits are an option, but they require conventional silicon components for tasks such as digitizing analog signals. These rigid modules tend to make devices less comfortable because they create hot spots or increase the device’s weight.
A team from the KAUST Computer, Electrical and Mathematical Science and Engineering Division in Saudi Arabia has spent four years investigating ways to improve the flexibility of silicon materials while retaining their performance.
“We are trying to integrate all device components—sensors, data management electronics, battery, antenna—into a completely compliant system,” explained Muhammad Hussain, Associate Professor of Electrical Engineering at KAUST. “However, packaging these discrete modules on to soft substrates is extremely difficult.”
The researchers developed a sensor containing narrow strips of aluminum foil that changes conductivity at different bending states.The university noted that these devices could monitor a patient’s breathing patterns or activity levels, and feature “high-mobility zinc oxide nanotransistors on silicon wafers thinned down lithographically to microscale dimensions for maximum flexibility.” Using 3D-printing techniques, the team encapsulated the silicon chips and foils into a polymer film backed by an adhesive layer, forming a decal.
Hussain and his colleagues explained that these e-stickers can be used for an array of applications by attaching or re-adhering to new (and different) locations. They used inkjet printing to write conductive wiring patterns on to different surfaces, such as paper or clothing.
“You can place a pressure-sensing decal on a tire to monitor it while driving and then peel it off and place it on your mattress to learn your sleeping patterns,” said Galo Torres Sevilla, first author of the findings and a KAUST Ph.D. graduate.
Hussain also noted that the decals have the potential for high-throughput manufacturing and could be deployed in many innovative ways.
“I believe that electronics have to be democratized—simple to learn and easy to implement. Electronic decals are a right step in that direction,” Hussain said.
