The innovative material paves the way for a new generation of wearable devices for intensive care

Image: Pictured are stretchable wearable devices placed on a newly developed material substrate (image courtesy of Raudel Avila/Rice University and Sun Hong Kim/Hanyang University)

Wireless modules integrating telecommunications and energy harvesting capabilities powered by radio frequency (RF) electronics are key to the development of stretchable skin-connected electronics. Despite their potential, these devices often face challenges with even minimal levels of deformation, which can change critical electrical properties such as the antenna’s resonance frequency, leading to reduced signal strength or power transfer efficiency. This issue is particularly important when using devices on dynamic surfaces such as human skin. To solve this problem, researchers have developed a new material that not only maintains constant signal strength, but also mimics skin movements, opening the door to more reliable and advanced wearable devices that provide continuous wireless connectivity without the need for batteries.

The material was developed by an international team of scientists from Rice University (Houston, Texas, USA) and Hanyang University (Seoul, South Korea) by embedding clusters of highly dielectric ceramic nanoparticles in a flexible polymer. This innovative material has been reverse-engineered to mimic the elasticity and movement pattern of human skin, while improving its dielectric properties to counteract the negative effects of movement on electronic interfaces, reduce energy loss and effectively dissipate heat. The strategic placement and distribution pattern of nanoparticles embedded in the substrate is crucial; the spacing and shapes of these particle clusters are intended to stabilize electrical properties and maintain the resonant frequency of RF components necessary for reliable operation.

Wearable technologies are revolutionizing healthcare by enabling innovative ways to monitor, diagnose and manage health. The smart clothing market, especially in the health and fitness space, is growing rapidly due to the transformative impact of these technologies. To explore practical applications of this new material, scientists constructed various stretchable wireless devices such as antennas, coils, and transmission lines. They tested these devices on both a newly developed substrate and a standard elastomer without ceramic nanoparticles. Their findings showed that the wireless operating range of their long-range communication systems exceeded that of any other comparable skin-interface systems previously reported.

Additionally, this material shows great potential to improve wireless connectivity between multiple wearable devices designed to suit different body parts and sizes. For example, the team created wearable bionic bands to be placed on the head, knee, arm, or wrist that can monitor a wide range of health data, including EEG and EMG signals, knee movements, and body temperature. In particular, a headband made of this material demonstrated exceptional stretchability – up to 30% for a small child’s head and 50% for an adult’s head – while still being able to transmit real-time EEG data over a wireless distance of 30 meters.

“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 are distributed within it when stretched to stabilize radio communications,” said Raudel Avila, assistant professor of mechanical engineering at Rice. “Stretchable skin-connected RF devices that seamlessly adapt to skin morphology and monitor key physiological signals require critical design of individual material systems and electronic components to achieve mechanical and electrical properties and performance that do not disrupt the user experience. As wearable devices continue to evolve and impact the way society interacts with technology, particularly in the context of health technology, the design and development of high-performance, stretchable electronics is becoming critical for stable wireless connectivity.

Related links:
Rice University
Hanyang University