The titanium ion moves away from the center of the unit cell (chosen as downward in the graphic), thus giving the unit cell a net dipole moment-with the positive end downward. Comparatively, a floor of the same size made of piezoelectric material would be much more expensive, since ceramics as a whole are difficult to manufacture, especially at that size (Howells).At temperatures below the Curie point, the crystal distorts to tetragonal symmetry. The floor displacement drives a flywheel that then powers a generator. This 270 square foot floor cost about $257,000, and uses a mechanical system rather than piezoelectric transducers (NYTimes). The dance floor flexes up to a few centimeters as dancers move creating up to twenty watts per person. The piezoelectric effect inherently relies on deformation to produce power, but sufficient deformation is accompanied by risk of material failure and interference with other critical systems such as wire connections and even pedestrian comfort (Howells).Ĭlub Watt in Rotterdam designed by Sustainable Dance Club uses a similar concept to generate ten percent of its energy use. Howells of the US Army when designing and testing the Heel Strike Generator. One such difficulty was encountered by Christopher A. Seungbum Hong at Argonne National Lab as well as other researchers has noted that the high voltages and resonant frequency make piezoelectric energy harvesting inefficient on top of other logistical difficulties. The qualities that make this technology exceptional in these fields make them unfavorable anywhere else (Wikipedia).Īpplications in commercial or personal electricity generation are one such example. Other modern applications are as time standards in watches, piezoelectric motors, vibrational dampeners, and inkjet ejectors. Guitar pickups and barbeque grill igniters are common examples where piezoelectric crystals are a staple, but they have also found a niche in vibrational analysis in fluids and heavy machinery. In modern times, the most common use has remained in audio equipment. Even with a piezoelectric component nearly every radio and television, it remained obscure well into the end of the twentieth century (McGahey). However, research began into alternatives and more effective manufacturing methods, but despite the invention of things such as piezoceramics and piezoelectric igniters, the technology was largely overshadowed by the discovery of radiation and vacuum tubes. Up to this point, the only piezoelectric material used was quartz, both because it was inexpensive and it was common. This competition spawned the first large private research and development firms (McGahey). As expected, companies like AT&T Bell Laboratories, GE, Federal Telegraph Company, and Westinghouse scrambled to file patents and compete for the market share in the new technological market. Piezoelectric materials also found their way into televisions and other electronics as audio filters and buzzers. Phonographs and radios, inventions that revolutionized society, utilized quartz crystals in their electronic components. The unique relationship with sound was expanded upon as interest increased in its unique powers. A current passed through one transducer emitted a high-frequency ping which would bounce off objects and then be picked up by another transducer sensitive enough to precisely convert the echo (McGahey). Scientists created piezoelectric transducers from quartz crystals sandwiched between steel plates. In the early 1900s, the converse of this was used in the first submarine sonars. Depending on the wave form of the voltage, sound could be generated. Later it was found that alternatively, the crystals would vibrate when a current was passed through them.

Thus, they were named piezoelectric crystals after the Greek word piezo meaning press (Wikipedia). These materials all had characteristic crystal structures formed from a lattice of molecules with asymmetric dipole moments that would respond to mechanical pressure. Certain materials such as quartz, salt, and even sugar would generate a voltage when placed under stress. This was first observed by Carl Linaeus and Franz Aepinus in the mid-1800s, but it was not truly understood until it was demonstrated by two French physicists, Jacques and Pierre Curie in 1880. The piezoelectric effect is a molecular phenomenon that can be observed at the macroscopic level as a change in electric potential that is created when a piezoelectric substance is deformed.

Piezo electricity