A new type of ferroelectric polymer that is exceptionally good at converting electrical energy into mechanical deformation is a promising high-performance motion controller or “actuator” with great potential for applications in medical devices, advanced robotics and precision positioning systems. A team of international researchers led by Penn State.
Mechanical deformation, i.e. how a material deforms when a force is applied, is an important property for an actuator, i.e. any material that changes or deforms when an external force such as electrical energy is applied. Traditionally, these actuator materials are rigid, but soft actuators such as ferroelectric polymers exhibit higher flexibility and environmental adaptability.
The work demonstrated the potential of ferroelectric polymer nanocomposites to overcome the limitations of traditional piezoelectric polymer composites and offers a promising direction for the development of soft actuators with improved deformation properties and mechanical energy density. Soft actuators are of particular interest to robotics researchers because of their strength, power, and flexibility.
“Potentially, we could now have a kind of soft robotics that we call artificial muscle,” said King Wang, professor of materials science and engineering at Penn State and co-author of the study, recently published in Nature. Materials . “This will allow us to have a soft material that can carry a high load in addition to a large deformation. So this material will look more like human muscles than those close to human muscles.”
However, there are several hurdles that need to be overcome before these materials can deliver on their promise, and possible solutions to these hurdles are proposed in the study. Ferroelectrics are a class of materials that exhibit spontaneous electrical polarization when an external electrical charge is applied, with the positive and negative charges in materials pointing to opposite poles. The deformation of these materials during a phase transition, in this case the conversion of electrical energy to mechanical energy, can completely change properties such as shape, making them useful as actuators.
A common application of a ferroelectric actuator is in an inkjet printer, where an electrical charge changes the shape of the actuator to precisely control tiny nozzles that apply ink to paper to create text and images.
While many ferroelectric materials are ceramics, they can also be polymers, a class of natural and synthetic materials made from many similar elements bonded together. For example, DNA is a polymer like nylon. The advantage of ferroelectric polymers is that they exhibit the enormous amount of electric field-induced stress required for activation. This stress is much higher than that produced by other ferroelectric materials used for actuators such as ceramics.
This property of ferroelectric materials, combined with its high level of flexibility, low cost and low weight compared to other ferroelectric materials, is of great interest to researchers in the growing field of soft robotics, the development of robots with flexible parts, and electronics. .
“In this study, we propose solutions to two major challenges in the soft material activation field,” Wang said. “One of them is how to improve the strength of soft materials. We know that soft materials that are polymers have the most deformation, but they generate much less force compared to piezoelectric ceramics.”
The second problem is that a ferroelectric polymer actuator usually requires a very high drive area; this is the force that causes changes in the system, such as a change in shape in the actuator. In this case, a strong driving field is required to generate the shape change of the polymer required for the ferroelectric response required to become an actuator.
One proposed solution to improve the performance of ferroelectric polymers was to develop a permeable ferroelectric polymer nanocomposite, a type of microscopic sticker attached to the polymer. By adding nanoparticles to polyvinylidene fluoride, a type of polymer, the researchers created a network of interconnected poles in the polymer.
This network made it possible to induce a ferroelectric phase transition in electric fields much lower than would normally be required. This was achieved using an electrothermal method using Joule heating, which occurs when an electric current passing through a conductor releases heat. Using Joule heating to induce a phase transition in a nanocomposite polymer resulted in only requiring less than 10% of the electric field strength typically required for a ferroelectric phase change.
“Typically, this tension and force in ferroelectric materials are inversely proportional to each other,” Wang said. Said. “Now we can combine them into one material, and we have developed a new approach to control it using Joule heating. Since the driving area will be much lower, less than 10%, so this new material can be used for medical devices, optical devices and soft robots. It can be used in many applications that require a low level of control to be effective.” Source
Source: Port Altele
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