Piezoelectric Effect in Liquids

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• For the first time, scientists have reported evidence of the piezoelectric effect in liquids.

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• The effect was found in pure 1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide – both ionic liquids (i.e. liquids made of ions instead of molecules) at room temperature.
• The reason the piezoelectric effect has only been expected in solids thus far is that the body being squeezed needs to have an organised structure, like the pyramids of quartz. Liquids don’t have such structure; instead, they take the shape of their container.
• The new finding challenges the theory that describes this effect as well as opens the door to previously unanticipated applications in electronic and mechanical systems.

What is the piezoelectric effect?

• In the piezoelectric effect, a body develops an electric current when it is squeezed. The piezoelectric effect was discovered in 1880, in quartz.
• Quartz is the most famous piezoelectric crystal. Quartz is silicon dioxide (SiO2). The quartz crystal consists of silicon and oxygen atoms at the four vertices of a three-sided pyramid; each oxygen atom is shared by two pyramids. These pyramids repeat themselves to form the crystal.
• It is used in this capacity in analog wristwatches and clocks. Such crystals are also used in cigarette lighters, electric guitars, TV remote controls, audio transducers, and other instruments where converting mechanical stress to a current is useful.
• When a mechanical stress is applied – i.e. when the crystal is squeezed – the position of the charge is pushed further from the centre, giving rise to a small voltage. This is the source of the effect.

New applications of this discovery

• Using this effect, the liquids can be used as lenses with dynamic focusing abilities

Source: TH