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Advances in Engineering with the Piezoelectric Effect

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Advances in Engineering with the Piezoelectric Effect

The Piezoelectric Effect

lighterThe piezoelectric effect, which comes from the Greek word “piezo” meaning to squeeze or press, converts mechanical stresses into electric current. The first demonstration of this effect was in 1880 when Pierre and Jacques Curie used various crystals to create electricity. It wasn’t until the invention of sonar however that piezoelectricity had its first application. Today the most common use of this application is cigarette lighters, where a button is depressed which in turn triggers a spring loaded hammer to hit a crystal. This action causes an electric current to flow across the crystal, a small gap and finally ignite the flowing gas. Recently engineers have attempted to design new piezoelectric devices that may be able to harvest the produced electricity and store it for use in various applications.

The Mechanical Engineering To Power Relationship

Every time a mechanical pressure is produced in motions such as walking, running or dancing, a type of electrical energy is produced known as piezoelectricity. When any pressure is applied to an object, a negative charge is produced on the expanding side while a positive charge is produced on the compressing side. Once the pressure is released, the current flows across the surface of the material. By using miniature versions of these devices, it is possible to harvest the energy from even slight vibrations, acquiring as much as 85 microwatts of power in just one receiver. This is achieved through cost-effective micro-electro-mechanical systems (MEMS).i This new approach assembles mechanical sensors and systems on a silicon substrate, which allows complete systems to be manufactured on a single chip. Mechanical engineers also found that vacuum bonding glass covers over the wafer dramatically increased the harvesting ability and power output of the chips. Right now the largest obstacle in installation of piezoelectric harvesters in every feasible surface is that they must be tuned to a fairly specific frequency, or vibration.ii This is because the harvesters typically operate best in a linear pattern, which is easily acquired in a lab, but in reality where vibrations are random the harvesters would need to be able to operate in a variable, or nonlinear, fashion.

Recent Studies In Piezoelectic

The most recent test of piezoelectric harvesting sensors was by two MIT graduates that installed sensors in a series of public farms in urban areas with the idea to harvest the piezoelectric principle that is seen in locations such as train stations, malls and concert or dance halls. One footstep can only produce enough electrical current to power two 60-watt light bulbs for about a second, so when this floor is spread over a greater area the results are more realistically usable. For example it would take about 28,500 steps to power a subway train forward for a little over a second.iii Recent advancements have shown indications that new versions of piezoelectric models can capture a larger bandwidth of vibrations that would be more easily applied in reality. One very interesting application would be in gyms where weights are constantly being dropped, ropes constantly being jumped and all kinds of mechanical pressures being applied and released.It would also be easier to tune to a bandwidth at a gym because the weights being lifted are relatively similar and are constantly repeated. More advances in mechanical engineering as well as electrical engineering utilizing this technology, could allow us to power devices we use daily by harnessing our daily movements. Remember, you need to crawl before you can walk, and crawling is movement.

i Ridden, Paul Gizmag “Researchers Show off Tiny Piezoelectric Energy Capture Sensor” January 7, 2010

ii Coxworth, Ben Gizmag “Piezoelectric Devices May Soon Be Able to Capture More Energy From Movement” February 24, 2012

iii Trimarchi How Stuff Works “Can House Music Solve the Energy Crisis?” July 28, 2011

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