Penn State’s Qiming Zhang in his laboratory. Photo: Tyler Henderson/Penn State.
Penn State’s Qiming Zhang in his laboratory. Photo: Tyler Henderson/Penn State.

Piezoelectric materials convert mechanical stress into electricity, or vice versa, and have found use in sensors, actuators and many other applications. But implementing piezoelectrics in polymers – materials composed of molecular chains and commonly used in plastics, drugs and more – can be difficult, according to Qiming Zhang, professor of electrical engineering at Penn State.

Zhang and a team of interdisciplinary researchers at Penn State have now developed a polymer with robust piezoelectric effectiveness, resulting in 60% more efficient electricity generation than previous iterations. They report their results in a paper in Science.

“Historically, the electromechanics coupling of polymers has been very low,” Zhang said. “We set out to improve this because the relative softness of polymers makes them excellent candidates for soft sensors and actuators in a variety of areas, including biosensing, sonar, artificial muscles and more.”

To create the material, the researchers deliberately implemented chemical impurities into the polymer. This process, known as doping, allows researchers to tune the properties of a material to generate desirable effects — provided they integrate the correct number of impurities. Adding too little of a dopant could prevent the desired effects from occurring, while adding too much could introduce unwanted traits that hamper the material’s function.

The doping distorts the spacing between the positive and negative charges within the polymer’s structural components. This distortion segregates the opposite charges, allowing the components to accumulate an external electric charge more efficiently. This accumulation enhances electricity transfer in the polymer when it is deformed, Zhang said.

To enhance the doping effect and ensure alignment of the molecular chains, the researchers stretched the polymer. According to Zhang, aligning the chains in this way produces a greater electromechanical response than from a polymer with randomly aligned chains.

“The efficiency of the polymer’s electricity generation was vastly increased,” Zhang said. “With this process, we achieved a 70% efficiency – a vast improvement from 10% efficiency before.”

This robust electromechanical performance, which is more common in stiff ceramic materials, could lead to a variety of applications for the flexible polymer. Because the polymer exhibits resistance to sound waves similar to that of water and human tissues, it could be applied for use in medical imaging, underwater hydrophones or pressure sensors. Polymers also tend to be more lightweight and configurable than ceramics, so this polymer could provide opportunities to explore improvements in imaging, robotics and more.

This story is adapted from material from Penn State, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.