For the first time ever, two chemists from Michigan State University have observed the piezoelectric effect in liquids. Their demonstration involved the application of pressure to an ionic liquid, which resulted in the release of electricity proportionate to the amount of pressure exerted.
According to a recently published paper in The Journal of Physical Chemistry Letters, Md. Iqbal Hossain and G. J. Blanchard have reported that the room-temperature ionic liquids, 1-butyl-3-methyl imidazolium bis(trifluoromethyl-sulfonyl)imide (BMIM+TFSI–) and 1-hexyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide (HMIM+TFSI–), generate a voltage when subjected to force while contained within a cell. However, the magnitude of the voltage was found to be smaller than that observed in quartz.
To the best of our knowledge, this is the first documented evidence of the direct piezoelectric effect occurring in a pure liquid.
The piezoelectric effect refers to the ability of certain materials to produce an electrical charge when subjected to mechanical stress. Conversely, these same materials will undergo deformation in shape when exposed to an electrical current. One way to better comprehend this scientific phenomenon is through the following practical example.
The gas lighter used for igniting gas stoves contains a tiny piezoelectric crystal, usually composed of ceramic or quartz, which is sandwiched between two metal plates. When the button on the lighter is pressed, a spring-loaded hammer strikes the crystal, causing it to deform due to the mechanical force applied.
As a consequence of this deformation, the crystal produces a voltage disparity between the two metal plates, creating a potent spark that is discharged across a spark gap to ignite the gas. Therefore, the gas lighter utilizes the piezoelectric effect to transform mechanical energy into electrical energy, which is discharged as a spark.
The piezoelectric effect is predominantly observed in solids due to the presence of a crystalline structure, where atoms or molecules are arranged in a consistent pattern.
According to the commonly accepted theory, it has been believed that when a crystal is subjected to mechanical tension or pressure, the lattice structure undergoes deformation, leading to a modification in the positions of charged particles, thereby generating a voltage. Since liquids and gases lack a well-defined and organized crystal structure, they were previously thought to be incapable of displaying the piezoelectric effect.
The recent discovery of the piezoelectric effect in liquids challenges the existing theory surrounding this phenomenon, highlighting the need for a more comprehensive understanding. In addition, experts suggest that piezoelectric materials in liquid form, especially those generated using ionic liquids, could be advantageous due to their superior environmental sustainability as compared to solid materials. Additionally, liquid piezoelectric materials could potentially allow for greater flexibility in device design, paving the way for new design possibilities.