Piezo composites with carbon fibers for motion sensors

An international research group has designed a novel, high-strength flexible device by combining piezoelectric composites with unidirectional carbon fiber (UDCF), an anisotropic material that provides strength only in the direction of the fibers. The new device transforms the kinetic energy of human movement into electricity, providing an efficient and reliable means for heavy-duty self-powered sensors.

Details of the group’s research were published in the journal. Little on December 14, 2023.

Movement speech involves converting the energy of human movement into measurable electrical signals and is something that may be crucial to ensuring a sustainable future.

“Everyday items, from protective equipment to sports equipment, are connected to the Internet as part of the Internet of Things (IoT), and many of them are equipped with sensors that collect data,” says Fumio Narita, co-author of the study. and professor at the Graduate School of Environmental Studies at Tohoku University. “And effective integration of these IoT devices into personal equipment requires innovative solutions in power management and material design to ensure durability and flexibility.”

Mechanical energy can be used thanks to the ability of piezoelectric materials to generate electricity when physically stressed. Meanwhile, carbon fiber lends itself to applications in the aerospace and automotive industries, sports equipment, and medical equipment due to its durability and lightness.

“We wondered if personal protective equipment, flexible using a combination of carbon fiber and a piezoelectric composite, could offer comfort, greater durability and detection capabilities,” says Narita.

The group fabricated the device using a combination of unidirectional carbon fiber fabric (UDCF) and potassium sodium niobate (KNN) nanoparticles mixed with epoxy resin (EP). The UDCF served as electrode and directional reinforcement.

The device called UDCF/KNN-EP lived up to their expectations. Tests revealed that it could maintain high performance even after being stretched more than 1,000 times.

It has been shown to be able to withstand a much higher load when pulled along the grain direction compared to other flexible materials. Additionally, when subjected to impacts and stretched perpendicular to the fiber direction, it outperforms other piezoelectric polymers in terms of energy production density.

The mechanical and piezoelectric responses of UDCF/KNN-EP were analyzed using multiscale simulations in collaboration with Professor Uetsuji’s group at the Osaka Institute of Technology.

The UDCF/KNN-EP will help drive the development of flexible and self-powered IoT sensors, leading to advanced multifunctional IoT devices.

Narita and his colleagues are excited about their technological advances.

“CF/KNN-EP was integrated into sports equipment and accurately detected the impact of catching a baseball and the frequency of a person’s steps. In our work, the high resistance of CF was taken advantage of to improve sustainability and reliability of battery-free sensors while maintaining their directional stretchability and provides valuable information and guidance for future research in the field of motion detection.”