The piezoelectric effect in liquids

Context: A pair of chemists at Michigan State University has observed the 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, describe accidently observing the property while studying ionic liquids.

More on news: The researchers were studying properties of ionic liquids, which are made from salts with unsymmetrical, flexible organic cations and symmetrical weakly coordinating anions. Electricity builds up within them and is released when they are pressed or squeezed.

The liquid piezoelectric material was discovered as the researchers applied pressure with a piston to a sample of an ionic liquid in a cylinder. To their surprise, they found that this led to the release of electricity. They also found that the amount of electricity released was proportional to the amount of pressure applied.

Further testing showed that the optical properties of the ionic liquids changed when they released electricity. In some instances, the researchers found changes in how the liquid bent light.

Piezoelectric effect 

The Piezoelectric effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress.

How it works

  • The Piezoelectric effect arises due to the unique crystal structure of certain materials, such as quartz, tourmaline, and Rochelle salt.
  • These materials have a crystal lattice structure that is asymmetric, meaning that their positive and negative charges are not evenly distributed throughout the crystal.
  • When an external force is applied to these materials, it causes a shift in the positions of the positive and negative charges, resulting in an electric polarization.
  • The magnitude and direction of the electric charge generated by the Piezoelectric effect depend on the type and orientation of the crystal, as well as the magnitude and direction of the applied force.

Applications of Piezoelectric effect

The Piezoelectric effect is used in a variety of applications, including:

  • Medical ultrasound: Piezoelectric crystals are used to generate and receive high-frequency sound waves, which are used to image internal organs and tissues.
  • Sensors: Piezoelectric materials can be used as sensors to measure pressure, force, acceleration, and other physical quantities. For example, piezoelectric sensors are commonly used in industrial automation and automotive applications to measure vibrations and monitor machine health.
  • Actuators: Piezoelectric materials are used to convert electrical energy into mechanical motion, such as in inkjet printers and fuel injectors. For example, piezoelectric actuators are used in inkjet printers to control the flow of ink and in camera lenses to adjust the focus.
  • Energy Harvesting: Piezoelectric materials can be used to convert mechanical vibrations or movements into electrical energy. This can be useful for powering small electronic devices, such as sensors or wireless transmitters, in remote or inaccessible locations.
  • Medical Devices: Piezoelectric materials are used in various medical devices, such as ultrasound machines and pacemakers. In ultrasound machines, piezoelectric crystals generate high-frequency sound waves that are used to visualize internal organs and tissues. In pacemakers, piezoelectric crystals are used to generate electrical pulses that regulate the heartbeat.
  • Acoustic Devices: Piezoelectric materials can be used in acoustic devices, such as microphones and speakers. In microphones, piezoelectric crystals are used to convert sound waves into electrical signals, while in speakers, they are used to convert electrical signals into sound waves.
  • Structural Health Monitoring: Piezoelectric sensors can be used for structural health monitoring of bridges, buildings, and other infrastructure. By measuring the mechanical strain or stress on the structure, piezoelectric sensors can detect cracks, deformations, or other signs of damage or wear.


  • The Piezoelectric effect is reversible, meaning that if an electric field is applied to the crystal, it will deform and produce a mechanical strain.
  • In conclusion, the Piezoelectric effect is a unique and important phenomenon that has found numerous applications in modern technology. Its ability to generate an electric charge in response to applied mechanical stress makes it a valuable tool in fields such as medicine, engineering, and materials science.

UPSC PYQ (2021)

With reference to street-lighting, how do sodium lamps differ from LED lamps?

  1. Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps.
  2. As street-lights, sodium lamps have longer life span than LED lamps.
  3. The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant colour advantages in street-lighting.

Select the correct answer using the code given below.

(a) 3 only

(b) 2 only

(c) 1 and 3 only

(d) 1, 2 and 3

Answer – c)

Practice question

With reference to piezoelectric effect, consider the following statements:

  1. It can cause spontaneous emission of electrons from a material when exposed to light.
  2. It is the ability of a material to generate an electric charge in response to an applied mechanical stress or pressure.
  3. It can only be observed in solid metals. 

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2 only

(c) 2 and 3 only

(d) 1, 2 and 3

Answer – b)

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