Ferroelectric polymer nanocomposites could revolutionize soft robotics

Researchers from Penn State and an international team have developed a highly efficient ferroelectric polymer capable of converting electrical energy into mechanical strain. This breakthrough could revolutionize the field of actuators, which are materials that change or deform when an external force, such as electrical energy, is applied. Unlike traditional rigid actuators, this new type of ferroelectric polymer is soft, flexible, and adaptable to different environments.

The study showcased the potential of ferroelectric polymer nanocomposites to surpass the limitations of piezoelectric polymer composites commonly used in actuators. These nanocomposites offer improved strain performance and mechanical energy density, making them promising candidates for the development of high-performance soft actuators. Soft actuators, known for their strength, power, and flexibility, are particularly valuable in robotics research.

Qing Wang, a professor of materials science and engineering at Penn State and co-corresponding author of the study published in Nature Materials, highlighted the possibility of creating artificial muscles using this new technology. By mimicking the properties of human muscles, these soft materials could carry heavy loads while maintaining a large strain.

While the potential of these ferroelectric polymer actuators is promising, there are still challenges to overcome. The researchers proposed solutions to these obstacles in the study. Ferroelectrics are materials that exhibit spontaneous electric polarization when subjected to an external electric charge, with positive and negative charges gathering at different poles. The phase transition during the conversion of electrical energy to mechanical energy can significantly alter the material’s properties, including its shape, making it useful as an actuator.

One of the most common applications of ferroelectric actuators is in inkjet printers, where electrical charge manipulation changes the shape of the actuator to precisely control the nozzles that deposit ink on paper, enabling the formation of text and images.

Ferroelectric materials can exist in the form of ceramics or polymers. While ceramics are commonly used, ferroelectric polymers offer several advantages. They exhibit a remarkable amount of electric-field-induced strain, making them ideal for actuation. This strain is significantly higher than that generated by ceramic-based ferroelectric materials used in actuators.

The unique properties of ferroelectric polymers, including high flexibility, lower cost compared to other materials, and lightweight nature, have attracted the attention of researchers in the field of soft robotics. Soft robotics focuses on designing robots with flexible components and electronics.

Addressing the challenges in soft material actuation, Qing Wang and the team proposed solutions in their study. The first challenge was to improve the force generated by soft materials. While soft actuation polymers have high strain, they typically produce less force compared to piezoelectric ceramics. The second challenge involved the high driving field required for ferroelectric polymer actuators to undergo the necessary shape change for actuation.

To enhance the performance of ferroelectric polymers, the researchers developed a percolative ferroelectric polymer nanocomposite. This involved incorporating nanoparticles into a polymer called polyvinylidene fluoride, creating an interconnected network of poles within the material. By utilizing an electro-thermal method called Joule heating, which produces heat when electric current passes through a conductor, the researchers induced the ferroelectric phase transition in the nanocomposite polymer at significantly lower electric fields. The phase transition required less than 10% of the typical electric field strength.

This innovative approach allowed for the integration of strain and force in a single material, overcoming the usual inverse relationship between the two properties. With the reduced driving field, less than 10%, the new material can find applications in various fields that require low driving fields, such as medical devices, optical devices, and soft robotics.

Source: Pennsylvania State University

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