Some materials in nature can significantly change in size and shape — or deform — like a rubber band when an electrical signal is sent. The materials act as an energy converter that deforms when an electrical signal is sent through or supplies electricity when manipulated. This is called piezoelectricity and is useful in creating sensors and laser electronics, among several other end uses. These naturally occurring materials are rare and consist of stiff crystalline structures that are often toxic — three distinct drawbacks for human applications.

Manmade polymers offer steps toward alleviating these pain points by eliminating material scarcity and creating soft polymers capable of bending and stretching — known as soft elastomers — but previously, those soft elastomers lacked significant piezoelectric attributes.

Researchers have demonstrated “giant flexoelectricity” in soft elastomers that could improve robot movement range and make self-powered pacemakers a real possibility. This theory engineers a connection between electricity and mechanical motion in soft, rubber-like materials. While some polymers are weakly piezoelectric, there are no soft, rubber-like materials that are piezoelectric. The term for these multifunctional soft elastomers with increased capability is “giant flexoelectricity”; in other words, boosting flexoelectric performance in soft materials.

In most soft rubber materials, flexoelectricity is quite weak but by rearranging the chains in unit cells on a molecular level, the theory shows that soft elastomers can attain flexoelectricity of nearly 104 times the conventional amount. Human-like robots made with soft elastomers that contain increased flexoelectric properties would be capable of a greater range of motion to perform physical tasks. Pacemakers implanted in human hearts and utilizing lithium batteries could instead be self-powered as natural movement generates electrical power.

The mechanics of soft elastomers generating and being manipulated by electrical signals replicates a similar function observed in human ears. Sounds hit the ear drum, which then vibrates and sends electrical signals to the brain, where they are interpreted. In this case, movement can manipulate soft elastomers and generate electricity to power a device on its own. This process of self-generating power by movement is a step up from a typical battery.

Efforts to improve on the flexoelectric effect in soft elastomers will be the focus of further study.

For more information, contact Nicole Johnson at nmjohnson@ uh.edu; 713-743 1589.


Motion Design Magazine

This article first appeared in the August, 2021 issue of Motion Design Magazine.

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