RMIT Develops Durable Piezoelectric Nylon-11 Film for Energy Harvesting
RMIT University researchers have developed a flexible film made from nylon-11 that generates electricity when subjected to mechanical stress, a phenomenon known as piezoelectricity. The material has demonstrated significant durability, maintaining functionality after being repeatedly compressed, folded, stretched, and even driven over by a car. This development aims to provide a resilient alternative for energy harvesting in various applications.
Researchers at RMIT University have created a thin, flexible nylon-film device capable of generating electricity from mechanical actions such as compression, bending, or tapping, addressing a challenge with the durability of existing energy-harvesting plastics.
Breakthrough in Piezoelectric Plastics
The innovation, led by Distinguished Professor Leslie Yeo, Associate Professor Amgad Rezk, and PhD researcher Robert Komljenovic, utilizes nylon-11, an industrial plastic, to produce an electrical charge. This offers a durable alternative to existing piezoelectric components, which are already employed in various systems, including vehicle fuel injectors, parking sensors, and airbag systems.
How it Works: Re-engineering Nylon-11
The device leverages piezoelectricity, a property where certain materials, including quartz, some ceramics, and bone, produce an electrical charge when compressed, pressed, or vibrated. Standard nylon typically does not efficiently convert movement into electricity.
The RMIT team successfully reengineered nylon-11 at a molecular level to significantly enhance its piezoelectric properties. The manufacturing process involves applying high-frequency sound vibrations and a strong electric field simultaneously as the nylon-11 precursor solution solidifies. This unique technique promotes a more ordered molecular structure, enhancing long-range crystal ordering, improving hydrogen-bond network ordering, and aligning molecular dipoles. These precise molecular alignments are crucial for strong piezoelectric behavior. The developed method is described as energy-efficient and scalable for potential industrial applications.
Unprecedented Durability and Performance
Laboratory tests emphatically demonstrated the film's resilience. It continued to function after being driven over by a car multiple times, folded, and stretched. Specifically, the films retained functionality after being compressed by a moving vehicle (with a 14,000 N load) and maintained a consistent response over 20,000 loading cycles.
Performance measurements showed that the electromechanically processed film generated 110 pC of charge under cyclic compression, achieving a peak-to-peak voltage of approximately 0.65 V and a power density of 12.5 µW cm−3. This represents a remarkable 400-fold increase over mechanically processed films. The piezoelectric voltage coefficient (g33) was reported at 427 × 10−3 Vm N−1, a value stated to surpass those previously reported for piezoelectric polymers. The researchers noted that the film's piezoelectric coefficient (d33) decreased with rising temperatures and humidity levels.
Versatile Applications and Eco-Friendly Benefits
The new nylon film could offer a durable alternative for existing piezoelectric applications in vehicles. The technology is envisioned for use in self-powered sensors in challenging environments, such as roads and infrastructure, where constant compression occurs. Other potential applications include:
- Wearable technology
- Smart surfaces
- Flexible electronics
- Sports equipment
This innovation could also enable new methods for charging small devices by harvesting energy from compression generated by people, machines, or vehicles. Furthermore, nylon-11 presents a non-fluorinated, environmentally favorable alternative to PVDF, contributing to carbon emission reduction by utilizing ambient energy from movement and pressure.
Next Steps: Scaling Up and Commercialization
The research team plans to scale up the technology for larger applications. They are actively exploring collaborations with industry partners for commercialization, indicating interest in applications ranging from flexible electronics to sports equipment.