Flex education: Researchers enhance electromechanical behaviour in a flexible polymer

Mechanical stress can be converted into electricity through the use of piezoelectric materials for successful applications in, for instance, sensors, semiconductors and actuators. Implementing piezoelectrics in polymers, however, can be difficult.

Qiming Zhang, distinguished professor of electrical engineering, and a team of interdisciplinary researchers led by The Pennsylvania State University, US, have developed a polymer with robust piezoelectric effectiveness. The latest iterations are showing an up to 70 per cent increase in efficient electricity generation and their results have been published in the prestigious publication Science . 

Speaking to Penn States Gabrielle Stewart, who broke the story, Zhang said: “Historically, the electromechanics coupling of polymers has been very low. 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.”

A specific number of chemical impurities were deliberately implemented into the polymer to create a new piezoelectric material. Known as ‘doping’ this is a process that enables researchers to fine-tune the properties of a material and generate certain effects. Doping distorts the spacing between positive and negative charges within a polymer’s structural components: ‘The distortion segregates the opposite charges, allowing the components to accumulate an external electric charge more efficiently,’ Stewart wrote.

The particular accumulation used by Zhang and his team was intended to enhance electricity transfer during deformation. He then enhanced the doping effect to ensure molecular alignment before stretching the polymer to promote a more distinct electromechanical response than from a polymer with randomly aligned chains.

The efficiency of the polymer’s electricity generation was vastly increased. An early iteration generated just a 10 per cent improvement in efficiency, with the latest iteration recorded a 70 per cent improvement. Such electromechanic performances could enable industrial and commercial applications for the flexible polymer. The polymer used exhibits resistance to soundwaves similar to that of water and human tissues and could therefore be suitable for use in medical applications, as well as underwater hydrophones, robotics and pressure sensors.

A full list of co-contributors to this work is included in the named authors. The research was also supported by the US Office of Naval Research.