Researchers discovered piezoelectricity in two different liquids. (Image Credit: The Journal of Physical Chemistry Letters (2023). DOI: 10.1021/acs.jpclett.3c00329)
Michigan University chemists accidentally discovered piezoelectric liquids for the first time while observing ionic liquids. This discovery could lead to interesting new applications, including piezo-hydraulics and electrically controlled optics. But nobody knows how these liquids work or about their potential capabilities. Moreover, the Boffins discovered piezoelectricity in 1880, and it has applications in inkjet printers, sonar equipment, diesel fuel injectors, pressure sensors, actuators, and more.
Until recently, piezoelectric materials were solid (crystals, ceramic, and biological matter), and they accumulated an electric charge that gets released due to applied stress. These materials also exhibit a converse piezoelectric effect, in which applied electricity alters their shape. The team discovered the liquids experienced something similar. Its optical properties dramatically changed when an electric current passed through.
The team discovered piezoelectric liquids when conducting experiments with ionic liquid salts. They found that each ionic liquid produced electricity as a piston compressed them in a cylinder. This effect's strength was proportional to the force applied, which proved to be a shocking experience. In addition, the team noticed an induced free charge density gradient effect in the liquid that achieves the inverse piezoelectric phenomena necessary in piezoelectric materials.
Before this discovery, researchers believed that only crystalline piezoelectric materials existed and didn't have inversion symmetry. These crystals are highly organized, which also meant that researchers didn't try to search for those materials among liquids. As a result, the team has no idea how piezoelectricity happens in liquids. But, they think applying force against ionic liquids makes the electric charges separate within the fluids, producing an electric current. They also want to determine if other materials exhibit higher conductivity since their tests showed a piezoelectric effect that's an order of magnitude smaller than quartz.
The team tested the liquids for potential applications, including optics, by inserting them inside a lens-shaped container. After applying electricity, the focal point of the lens changed. They noted the finding could require "modification to account for experimental observations." There's still uncertainty if these piezoelectric liquids can be modified to boost the piezoelectric effects' speed or strength. Plus, they still aren't sure how the electric charge flows within the fluids.
Have a story tip? Message me at: http://twitter.com/Cabe_Atwell