A novel flexible device, merging piezoelectric composites with unidirectional carbon fibre, transforms kinetic energy from human motion into electricity.

An international research group has engineered a high-strength flexible device by combining piezoelectric composites with unidirectional carbon fibre (UDCF). The novel device transforms kinetic energy from human motion into electricity, offering an efficient and reliable means for self-powered sensors. The integration of such technology is pivotal for advancing the Internet of Things (IoT) and enhancing the capabilities of wearable devices.

Harnessing human motion

Motion detection, the process of converting energy from human motion into measurable electrical signals, is integral in creating a sustainable future. The proliferation of IoT devices, ranging from protective gear to sports equipment, necessitates innovative solutions in power management and material design to ensure durability and flexibility.

Fumio Narita, co-author of the study and professor at Tohoku University’s Graduate School of Environmental Studies in Japan, emphasises the importance of effectively integrating IoT devices into personal gear.

Integrating materials

The device’s foundation lies in the combination of piezoelectric materials and unidirectional carbon fibre. Piezoelectric materials exhibit the ability to generate electricity when physically stressed – ideal for converting mechanical energy. Carbon fibre is also renowned for its durability and lightness, finding applications in aerospace, automotive, sports, and medical industries.

The researchers envisioned creating flexible personal protective equipment by leveraging the unique properties of carbon fibre and piezoelectric composites. The resulting device, named UDCF/KNN-EP, was fabricated using unidirectional carbon fibre fabric (UDCF) and potassium sodium niobate (KNN) nanoparticles mixed with epoxy resin. UDCF served a dual purpose, functioning as both an electrode and a directional reinforcement.

Performance and durability

The UDCF/KNN-EP device exceeded expectations in terms of performance and durability, according to the researchers. Through rigorous testing, it demonstrated the ability to maintain high performance even after being stretched over 1,000 times. Notably, it exhibited enhanced load-bearing capabilities when pulled along the fibre direction compared to other flexible materials. Furthermore, when subjected to impacts and stretching perpendicular to the fibre direction, it outperformed other piezoelectric polymers in energy output density, according to the team.

The researchers utilised multiscale simulations, collaborating with Professor Uetsuji’s group at the Osaka Institute of Technology, to analyse the mechanical and piezoelectric responses of UDCF/KNN-EP. This comprehensive approach ensures a thorough understanding of the device’s behaviour and performance under various conditions.

Applications in sports equipment and beyond

Excitingly, the UDCF/KNN-EP device has practical applications beyond its core functionality. Integrated into sports equipment, it accurately detected impacts from catching a baseball and monitored a person’s step frequency. Leveraging the high strength of carbon fibres enhances the sustainability and reliability of battery-free sensors while maintaining directional stretchability. This breakthrough paves the way for the development of flexible self-powered IoT sensors, contributing to the evolution of advanced multifunctional IoT devices.

The integration of piezoelectric composites with unidirectional carbon fibre marks a significant milestone in wearable technology. According to the researchers, the UDCF/KNN-EP device not only showcases exceptional performance and durability but also opens avenues for a new era of sustainable and self-powered IoT sensors. As technology continues to advance, the fusion of materials science and energy harvesting holds immense promise for creating innovative solutions that redefine the capabilities of wearable devices.