US scientists are a step closer to producing a new generation of energy conversion devices, thanks to an advance in liquid crystal (LC) technology.

Antal Jákli, at Kent State University, and colleagues have made use of a property called flexoelectricity, where materials, such as LCs, convert mechanical energy into electrical energy when they are flexed.

The LCE's volume swells by around a factor of two when it absorbs the bent-core LCs

Bent-core nematics (BCNs) - LCs made from banana-shaped molecules - are particularly flexoelectric but because of their fluidity, they are not robust or flexible enough to use in energy conversion devices.

To get around this problem, the team used the rubbery properties of a LC elastomer (LCE) to provide a flexible support for the BCN. By swelling the LCE with a BCN, they obtained lightweight films that preserve the pure BCN's strong flexoelectricity but in a more robust and flexible form. The new BCN-LCE material can be used over a wider temperature range than the pure BCN, increasing its viability for device application.

Flexoelectricity is also possible with some ceramic materials but 'such materials tend to brittle and are difficult to work with, particularly in the form of thin films,' says Mark Wilson, an expert in LCs and soft matter chemistry from Durham University, UK. This new material offers clear advantages, he adds: 'The lightweight nature of the films and relative ease of processing could open the way for the production of very lightweight devices for recovering small amounts of electrical energy from a mechanical distortion.'

It will still be some time before we see devices made from these materials, says Jákli. 'This area is still in its infancy,' he comments. 'But we can imagine devices that can generate electricity when pasted over some periodically moving parts on the body or an engine.'

Amaya Camara-Campos

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