The researchers have developed a self-powered, stretchable system that will be...
The researchers have developed a self-powered, stretchable system that will be used in wearable health-monitoring and diagnostic devices.
Source: Penn State College of Engineering

Micro-supercapacitors to self-power wearables

A stretchable system that can harvest energy from human breathing and motion for use in wearable health-monitoring devices may be possible, according to an international team of researchers, led by Huanyu “Larry” Cheng, Dorothy Quiggle Career Development Professor in Penn State's Department of Engineering Science and Mechanics.

According to Cheng, current versions of batteries and supercapacitors powering wearable and stretchable health-monitoring and diagnostic devices have many shortcomings, including low energy density and limited stretchability.

“This is something quite different than what we have worked on before, but it is a vital part of the equation,” Cheng said, noting that his research group and collaborators tend to focus on developing the sensors in wearable devices. “While working on gas sensors and other wearable devices, we always need to combine these devices with a battery for powering. Using micro-supercapacitors gives us the ability to self-power the sensor without the need for a battery.”

An alternative to batteries, micro-supercapacitors are energy storage devices that can complement or replace lithium-ion batteries in wearable devices. Micro-supercapacitors have a small footprint, high power density, and the ability to charge and discharge quickly. However, according to Cheng, when fabricated for wearable devices, conventional micro-supercapacitors have a “sandwich-like” stacked geometry that displays poor flexibility, long ion diffusion distances and a complex integration process when combined with wearable electronics.

This led Cheng and his team to explore alternative device architectures and integration processes to advance the use of micro-supercapacitors in wearable devices. They found that arranging micro-supercapacitor cells in a serpentine, island-bridge layout allows the configuration to stretch and bend at the bridges, while reducing deformation of the micro-supercapacitors — the islands. When combined, the structure becomes what the researchers refer to as "micro-supercapacitors arrays."

“By using an island-bridge design when connecting cells, the micro-supercapacitor arrays displayed increased stretchability and allowed for adjustable voltage outputs,” Cheng said. “This allows the system to be reversibly stretched up to 100%.”

By using non-layered, ultrathin zinc-phosphorus nanosheets and 3D laser-induced graphene foam — a highly porous, self-heating nanomaterial — to construct the island-bridge design of the cells, Cheng and his team saw drastic improvements in electric conductivity and the number of absorbed charged ions. This proved that these micro-supercapacitor arrays can charge and discharge efficiently and store the energy needed to power a wearable device.

The researchers also integrated the system with a triboelectric nanogenerator, an emerging technology that converts mechanical movement to electrical energy. This combination created a self-powered system. “When we have this wireless charging module that’s based on the triboelectric nanogenerator, we can harvest energy based on motion, such as bending your elbow or breathing and speaking,” Cheng said. “We are able to use these everyday human motions to charge the micro-supercapacitors.”

By combining this integrated system with a graphene-based strain sensor, the energy-storing micro-supercapacitor arrays — charged by the triboelectric nanogenerators — are able to power the sensor, Cheng said, showing the potential for this system to power wearable, stretchable devices.

The research was published in Nano Energy.

Subscribe to our newsletter

Related articles

Wearable devices set to diagnose preeclampsia or epilepsy

Wearable devices set to diagnose preeclampsia or epilepsy

Transforming how common health conditions are diagnosed using point-of-care and wearable bio diagnostic devices is the goal of a new University of South Australia project.

3D printed sensor invented for wearables

3D printed sensor invented for wearables

Researchers have utilized 3D printing and nanotechnology to create a durable, flexible sensor for wearable devices to monitor everything from vital signs to athletic performance.

Hybrid materials advance wearable devices

Hybrid materials advance wearable devices

We spoke to wearables and medical device expert Professor John Rogers about the benefits, challenges, trends and innovation within the sector.

Sensor warns of impending COVID-19 cytokine storm

Sensor warns of impending COVID-19 cytokine storm

Scientists report preliminary results on a sweat sensor that acts as an early warning system for an impending cytokine storm, which could help doctors more effectively treat patients.

Sticker detects cystic fibrosis in newborn's sweat

Sticker detects cystic fibrosis in newborn's sweat

Researchers have developed a novel skin-mounted sticker that absorbs sweat and then changes color to provide an accurate, easy-to-read diagnosis of cystic fibrosis within minutes.

A new medical device for monitoring vital signs

A new medical device for monitoring vital signs

A new device consisting of a 3D-printed wristband can remotely monitor patients' vital signs, such as body temperature, oxygen saturation, pulse, and respiratory rate.

Harvesting energy from radio waves to power wearables

Harvesting energy from radio waves to power wearables

Researchers have developed a way to harvest energy from radio waves to power wearable devices.

Wearable monitors jaundice-causing bilirubin in newborns

Wearable monitors jaundice-causing bilirubin in newborns

Researchers have developed the first wearable devices to precisely monitor jaundice, a yellowing of the skin caused by elevated bilirubin levels in the blood that can cause severe medical conditions in newborns.

Sensor detects signs of burnout in sweat

Sensor detects signs of burnout in sweat

Engineers have developed a wearable sensing chip that can measure the concentration of cortisol – the stress hormone – in human sweat.

Popular articles

Subscribe to Newsletter