New polymer material can act as ‘muscle’ for robots

Photo Credit: Adobe Stock/TensorSpark

A new type of ferroelectric polymer said to be “exceptionally good” at converting electrical energy into physical motion could be used to create muscles for robots, according to a team of international researchers led by Penn State in Pennsylvania.

Supported in part by the United States Department of Energy, the research, which was recently published as a study in Nature Materials, demonstrated that ferroelectric polymer nanocomposites – materials that demonstrate a spontaneous electric polarization when an external electric charge is applied – can outperform traditional piezoelectric polymer composites, offering a promising avenue for the development of soft actuators with enhanced strain performance and mechanical energy density. Soft actuators – which change shape when an external force, like an electrical charge, is applied – are especially of interest to robotics researchers due to its strength, power, and flexibility.

While many ferroelectric materials are ceramics, the research team said, they also can be polymers – for example, both DNA and nylon are polymers.

“In this study we proposed solutions to two major challenges in the soft material actuation field,” said study co-author Qing Wang, Penn State professor of materials science and engineering. “One is how to improve the force of soft materials. We know soft actuation materials that are polymers have the largest strain, but they generate much less force compared to piezoelectric ceramics.”

The second challenge is that a ferroelectric polymer actuator typically needs a very high driving field, which is a force that imposes a change in the system, such as the shape change in an actuator. In this case the high driving field is necessary to generate the shape change in the polymer required for the ferroelectric reaction needed to become an actuator.

The research team’s solution was to improve the performance of ferroelectric polymers by developing a percolative ferroelectric polymer nanocomposite – similar to a microscopic sticker attached to the polymer. By incorporating nanoparticles into polyvinylidene fluoride, the researchers created an interconnected network of poles within the polymer, allowing a shape change to be induced with less than 10 per cent of the energy typically needed for ferroelectric phase change.

“Potentially we can now have a type of soft robotics that we refer to as artificial muscle,” Wang said. “This would enable us to have soft matter that can carry a high load in addition to a large strain. So that material would then be more of a mimic of human muscle, one that is close to human muscle.”

Aside from advanced robotics, Wang continued, other applications for the polymers could include medical devices and precision positioning systems.

Source: Penn State