A Stretchy Skin-Like Material, Embedded with Nanoparticles, Could Deliver Better Wireless Wearables

Researchers from Hanyang University, Rice University, Sungkyunkwan University (SKKU), Korea's Electronics and Telecommunications Research Institute, and the Korea Research Institute of Chemical Technology (KRICT) have designed a skin-like material that, they say, can deliver better wearable electronics — by avoiding signal problems as the wearer goes about their daily life.

"If you have ever been in a place with poor cellular reception or a very spotty Wi-Fi signal, you probably understand the frustration of weak signals," explains co-lead author Raudel Avila, assistant professor at Rice. "When we’re trying to communicate information, we work at specific frequencies: two antennas communicating with each other do so at a given frequency. So we need to ensure that that frequency does not change so that communication remains stable."

“The challenge of achieving this in systems designed to be mobile and flexible is that any change or transformation in the shape of those RF components causes a frequency shift," Avila continues, "which means you’ll experience signal disruption.

"Our team was able to combine simulations and experiments to understand how to design a material that can seamlessly deform like skin and change the way electrical charges distribute inside it when it is stretched so as to stabilize radio-frequency communication. In a way, we are carefully engineering an electrical response to a mechanical event."

The material developed by the researchers uses clusters of ceramic nanoparticles embedded in an elastic polymer, reverse-engineered to mimic how skin feels and moves. The key: its ability to also adjust its dielectric properties in order to fight back against energy loss and heat build-up that can affect wearables during motions. To prove their case, the team developed devices including an antenna, a coil, and a transmission line, and tested them both with and without the new material.

"When we put the electronics on the substrate and then we stretch or bend it, we see that the resonant frequency of our system remains stable," Avila says of the team's experiments. "We showed that our system supports stable wireless communication at a distance of up to 30 meters (~98 feet) even under strain.

"With a standard substrate, the system completely loses connectivity. As wearables continue to evolve and influence the way society interacts with technology, particularly in the context of medical technology, the design and development of highly efficient stretchable electronics become critical for stable wireless connectivity."

The team's work has been published in the journal Nature under closed-access terms.

Main article image courtesy of Raudel Avila/Rice University and Sun Hong Kim/Hanyang University.