Researchers find liquid that generates electricity upon applying force
Up until now, piezoelectric effect was seen only in solids. The observation in liquid raises new questions about its science.
Two chemists from the Michigan State university have demonstrated when pressure is applied to an ionic liquid, it releases electricity proportional to the amount of pressure applied, presenting the first observation of piezoelectric effect in liquids for the first time.
In their paper published in The Journal of Physical Chemistry Letters, Md. Iqbal Hossain and G. J. Blanchard claims 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–), produced a voltage upon the application of force when confined in a cell, with magnitude smaller than that seen in quartz.
“This is the first report to our knowledge of the direct piezoelectric effect in a neat liquid.”
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Explaining piezoelectric effect
Piezoelectric effect is the phenomenon where certain materials generate electricity when it is stretched. Conversely, when electricity is provided, the material undergoes a change in shape.
The scientific phenomenon can be better understood with this working example.
In gas lighter that we use to ignite gas stoves, there is a small piezoelectric crystal, typically made of quartz or ceramic, placed between two metal plates. When the button on the lighter is pressed, a small spring-loaded hammer strikes the crystal, applying a mechanical force that deforms the structure.
This deformation causes the crystal to generate a voltage difference between the two metal plates, resulting in a high voltage spark that is discharged through a spark gap to ignite the gas.
Thus, the piezoelectric effect is used here to convert mechanical energy into electric energy in form of spark.
Why piezoelectric effect seen usually in solids?
The piezoelectric effect is mostly noticed in solids because of the presence of crystalline structure, with atoms or molecules arranged in a uniform pattern.
Till now it was believed, according to the generally accepted theory, when a crystal is exposed to mechanical tension or pressure, the lattice structure deforms, causing a change in the positions of the charged particles, thus developing a voltage.
Because liquids and vapours lack well-defined and ordered crystal structure, they do not exhibit the piezoelectric effect.
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Why piezoelectric effect in liquid revolutionary discovery?
Now, with the observation of piezoelectric effect in liquid, the theory behind the phenomenon stands challenged, demanding better understanding.
Furthermore, the experts believe that liquid piezoelectric materials, particularly those produced with ionic liquids, could be helpful because they are more environmentally friendly than solid materials. They also point out that liquid piezoelectric materials may enable for greater variation in device shape, offering up new design possibilities.