Devices and Methods for Energy Conversion Based on the Giant Flexoelectric Effect in Non-Calamitic Liquid Crystals
Abstract: Recent results obtained by us on a new class of nematic liquid crystals – based on molecules with a bent-core or "banana-shaped" – have dramatically altered the situation. We find that not only is the bend flexoelectric coefficient of bent-core NLC's truly gigantic (more than three orders of magnitude larger than in rod-shaped nematics), but also that it is much larger than would be expected from microscopic models based simply on molecular geometry. This places at the threshold of practical technologies based on flexoelectricity
Applications: We conservatively estimated that a specific power density approaching 10W/g (watts per gram) is completely feasible. This is comparable to the current state-of-the-art for energy conversion in piezoelectric crystals, but would be achieved with soft fluid-like material. Finally, we note that although the figure listed above is useful for comparison with other technologies, because of the unique nature of flexo-electricity, i.e. coupling between electric polarization and molecular orientation, the most important figure of merit is actually power developed per unit area rather than volume. This should have a crucial impact for applications where large coverage by a thin layer of conformal active material is desired (or is the only feasible option). The efficiency of the energy conversion with the presently available materials is in the range of 1-10%. However, we emphasize that an order of magnitude increase of the flexoelectric coefficient – which, as mentioned above, can be reasonably anticipated – would lead to attractive values (>30-40%) for applications.
Advantages: Electrical generators or actuators based on our discovery would have advantages of light weight, low cost, dynamic shape conformability/flexible packaging, larger areal coverage, low profile, and human-person compatibility
Inventors: A. (Tony) Jakli; S. Sprunt; J. T. Gleeson, J. Harden
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