UPSC Express

What is Piezoelectricity?

• ‘Piezo’ meaning to press or to squeeze.
• Piezoelectric property essentially is based on the interplay between mechanical and electrical features of a material.
• Bonds that keep materials together are electrons and these electrons are the basis for electricity.
• Therefore there exists a connection between material mechanics and material electronics. Changing one will impact the other.
• Piezoelectricity is the generation of electric charges in certain solid materials in response to applied mechanical stress — such as the body’s motion, wind and water flow, or sound vibration.
• With mechanical stress–electricity interactions, sensors can be made that catch mechanical vibrations and transform those to an electrical signal.
• Further piezoelectric effect is completely reversible, which means when stress is applied, electricity is generated and when electricity is applied, stress is generated.
• Materials that show these properties include Quartz, topaz, human and animal bone tissue, fibres, different proteins etc.

Spider-silk as a Piezoelectric Nano fibre

• There are many materials in nature which have piezoelectric properties.
• Spider silk is a fibre secreted by spiders.
• Spider silk is the strongest natually-occurring fiber known with tensile strength comparable to that of high-grade steel.
• The nanogenerator harvests electricity out of spider silk.
• When pressure is applied, it leads to changes in the molecular structure of the material, making it capable of harvesting mechanical/biomechanical energy into green electricity.
• The nanogenerator is prepared by spraying water on spider silk and wrapping it around the pacemaker.
• Every time the heart beats, it will create external pressure on the spider silk, making it generate energy.
• While the pacemaker will keep the heart ticking, the heartbeat will in turn keep the pacemaker going.
• This makes spider-silk a self-powered, piezoelectric nanogenerator that can harvest green energy from various mechanical and biomechanical motions.

Why spider-silk in pacemaker?

• There are various ceramic or metal-oxide-based piezoelectric materials.
• But due to their brittleness and toxic nature, these materials have limitations for application inside the human body.
• Spider silk, however, is both biocompatible and biodegradable and is therefore perfect for being used inside the body.

Potential uses of Spider-silk nanofibres

• The spider-silk-based flexible nanogenerator is extremely sensitive to even minute pressure generated from body motions.
• This includes even the very small pressure arising from arterial pulse (signals arising out of small strains), throat movement during coughing, speaking, and drinking.
• This shows its potentiality in healthcare-monitoring applications.
• Its sensitiveness could also be used to monitor robotic applications.
• It can also for harvesting green energy and even for large-scale industrial applications.
• Devices made of these materials have the added advantage of size.
• Therefore it can externally be used for small electronic devices such as mobile phones, watches and calculators etc.