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Nanogenerators: PiezoelectricTransducersModern Measurement & Instrumentation Term Paper

Prepared by:

Falak Shah

(09bec082)-B6 batch

Under guidance of:

Ami Vora madam

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Nanogenerators: Piezoelectric transducers

Power is always an essential atrocity, and the need for same remains an un-ending

requirement .On the wheel of development of todaysmultifaceted technology, newer methods

are invented with a phenomenal pace. Generation of power is thus a technological infrastructurethat needs to be updated with the inventions. Here, a newer class of generators is being

introduced. In accordance to the miniaturization trend a miniature power generator namely,

Nanogenerator. Small scale electrical generator includes an elongated substrate and apiezoelectric fine wire. The piezoelectric fine wire is attached along a surface of the substrate.

Definition:Nanogenerator is an energy harvesting device converting the external kinetic energy

into an electrical energy based on the energy conversion by Nano-structured piezoelectricmaterial.

Working Principle: The working principle of nanogenerator will be explained for 2 different

cases: the force exerted perpendicular and parallel to the axis of the nanowire.When a piezoelectric structure is subjected to the external force by the moving tip, the

deformation occurs throughout the structure. The piezoelectric effect will create the electrical

field inside the nanostructure; the stretched part with the positive strain will exhibit the positiveelectrical potential, whereas the compressed part with the negative strain will show the negative

electrical potential. This is due to the relative displacement of cations with respect to anions in its

crystalline structure. As a result, the tip of the nanowire will have an electrical potentialdistribution on its surface, while the bottom of the nanowire is neutralized since it is grounded.

For the second case, a model with a vertically grown nanowire stacked between the ohmiccontact at its bottom and the schottky contact at its top is considered. When the force is applied

toward the tip of the nanowire, the uniaxial compressive is generated in the nanowire. Due to the

piezoelectric effect, the tip of the nanowire will have a negative piezoelectric potential,

increasing the Fermi level at the tip. Since the electrons will then flow from the tip to the bottom

through the external circuit as a result, the positive electrical potential will be generated at the

tip.

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Piezoelectric Materials Used:

ZnO

CdS

GaN

Applications:

Self-powered Nano/micro devices Smart Wearable Systems Implantable Telemetric Energy Receiver Energy harvesting vehicles

Relation for Voltage generation:

Maximum generated output voltage is

Proportional to: Deflection of tip of wire

Cube of radius of nanowire

Inversely proportional to: Length of nanowire & Permittivity