Piezoelectricity is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure and latent heat. It is derived from Ancient Greek πιέζω (piézō) 'to squeeze or press', and ἤλεκτρον (ḗlektron) 'amber'.
A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is a quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators. However, other piezoelectricity materials including polycrystalline ceramics are used in similar circuits.
A crystal filter allows some frequencies to 'pass' through an electrical circuit while attenuating undesired frequencies. An electronic filter can use quartz crystals as resonator components of a filter circuit. Quartz crystals are piezoelectric, so their mechanical characteristics can affect electronic circuits. In particular, quartz crystals can exhibit mechanical resonances with a very high Q factor. The crystal's stability and its high Q factor allow crystal filters to have precise center frequencies and steep band-pass characteristics. Typical crystal filter attenuation in the band-pass is approximately 2-3dB. Crystal filters are commonly used in communication devices such as radio receivers.
Louis Essen FRS O.B.E. was an English physicist whose most notable achievements were in the precise measurement of time and the determination of the speed of light. He was a critic of Albert Einstein's theory of relativity, particularly as it related to time dilation.
A quartz crystal microbalance (QCM) measures a mass variation per unit area by measuring the change in frequency of a quartz crystal resonator. The resonance is disturbed by the addition or removal of a small mass due to oxide growth/decay or film deposition at the surface of the acoustic resonator. The QCM can be used under vacuum, in gas phase and more recently in liquid environments. It is useful for monitoring the rate of deposition in thin film deposition systems under vacuum. In liquid, it is highly effective at determining the affinity of molecules to surfaces functionalized with recognition sites. Larger entities such as viruses or polymers are investigated as well. QCM has also been used to investigate interactions between biomolecules. Frequency measurements are easily made to high precision ; hence, it is easy to measure mass densities down to a level of below 1 μg/cm2. In addition to measuring the frequency, the dissipation factor is often measured to help analysis. The dissipation factor is the inverse quality factor of the resonance, Q−1 = w/fr ; it quantifies the damping in the system and is related to the sample's viscoelastic properties.
A crystal oven is a temperature-controlled chamber used to maintain the quartz crystal in electronic crystal oscillators at a constant temperature, in order to prevent changes in the frequency due to variations in ambient temperature. An oscillator of this type is known as an oven-controlled crystal oscillator This type of oscillator achieves the highest frequency stability possible with a crystal. They are typically used to control the frequency of radio transmitters, cellular base stations, military communications equipment, and for precision frequency measurement.
A thin-film bulk acoustic resonator is a device consisting of a piezoelectric material manufactured by thin film methods between two conductive – typically metallic – electrodes and acoustically isolated from the surrounding medium. The operation is based on the piezoelectricity of the piezolayer between the electrodes.
Walter Guyton Cady was a noted American physicist and electrical engineer. He was a pioneer in piezoelectricity, and in 1921 developed the first quartz crystal oscillator.
Quartz clocks and quartz watches are timepieces that use an electronic oscillator regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency, so that quartz clocks and watches are at least an order of magnitude more accurate than mechanical clocks. Generally, some form of digital logic counts the cycles of this signal and provides a numerical time display, usually in units of hours, minutes, and seconds.
Leonard Cutler (1928–2006), also known as Leonard S. Cutler, was a pioneer and authority on ultra-precise timekeeping devices and standards, and was well known for his work with quantum-mechanical effects. He was the co-inventor of the HP5060A Cesium Beam Clock, its successor the HP 5071A, and the two-frequency laser inferometer. He has also been praised for his crucial contributions to the design of the Allen Telescope Array.
Microelectromechanical system oscillators are devices that generate highly stable reference frequencies to measure time. The core technologies used in MEMS oscillators have been in development since the mid-1960s, but have only been sufficiently advanced for commercial applications since 2006. MEMS oscillators incorporate MEMS resonators, which are microelectromechanical structures that define stable frequencies. MEMS clock generators are MEMS timing devices with multiple outputs for systems that need more than a single reference frequency. MEMS oscillators are a valid alternative to older, more established quartz crystal oscillators, offering better resilience against vibration and mechanical shock, and reliability with respect to temperature variation.
Mack Alfred Breazeale was an American physicist particularly known for his work in ultrasonics and physical acoustics. Breazeale is widely regarded as one of the leading acousticians of the 20th century, highly accomplished in both theory and experiment. When he died, he was a retired Distinguished Research Professor and Senior Scientist at the National Center for Physical Acoustics at the University of Mississippi. Born in Leona Mines, Virginia, Breazeale grew up near Crossville, TN. Educated at Berea College, the Missouri School of Mines, and the Michigan State University, he was a tireless researcher and trained many others in the field of physics. Before his appointment at the National Center for Physical Acoustics, he was professor of physics at the University of Tennessee (1962-1995) and at Michigan State University (1957-1962). A longtime editor of the Journal of the Acoustical Society of America, he was a fellow of the Acoustical Society of America (ASA) and received its Silver Medal in 1988. He was a fellow of the Institute of electrical and Electronics Engineers and Great Britain's Institute of Acoustics, and had been a Fulbright Research Fellow in Stuttgart, Germany early in his career.
David Wayne Allan is an American atomic clock physicist and author of the Allan variance, also known as the two-sample variance, a measure of frequency stability in clocks, oscillators and other applications. He worked for the National Bureau of Standards in Colorado.
Andrei M. Shkel is a Professor of Mechanical and Aerospace Engineering at the University of California, Irvine. He was named Fellow of the Institute of Electrical and Electronics Engineers (IEEE) in 2014 "for contributions to micromachined gyroscopes". He served as the President of the IEEE Sensors Council (2020-2021). In 2021, he was elected to National Academy of Inventors (NAI) Fellow status. He is currently the Editor-in-Chief of the IEEE Sensors Letters.
Warren Perry Mason was an American electrical engineer and physicist at Bell Labs. A graduate of Columbia University, he had a prolific output, publishing four books and nearly a hundred papers. He was issued over two hundred patents, more than anyone else at Bell Labs. His work included acoustics, filters, crystals and ceramics, materials science, polymer chemistry, ultrasonics, bonding to semiconductors, internal friction, and viscoelasticity.
Susan Trolier-McKinstry is an American materials scientist. She is the Steward S. Flaschen Professor of Materials Science and Engineering and Electrical Engineering at Pennsylvania State University, Director of the W. M. Keck Smart Materials Integration Laboratory, and co-director of the Nanofabrication facility.
James (Jim) Gegan Miller is an American physicist, engineer, and inventor whose primary interests center around biomedical physics. He is currently a professor of physics, Medicine, and Biomedical Engineering, emeritus, at Washington University in St. Louis, where he holds the Albert Gordon Hill Endowed Chair in the Faculty of Arts and Sciences. He is notable for his interdisciplinary contributions to biomedical physics, echocardiography, and ultrasonics.
Nazanin Bassiri-Gharb is a mechanical engineer in the field of micro and nano engineering and mechanics of materials. She is the Harris Saunders, Jr. Chair and Professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology in Atlanta, Georgia. Bassiri-Gharb leads the Smart Materials, Advanced Research and Technology (SMART) Laboratory at Georgia Tech. Her research seeks to characterize and optimize the optical and electric response of interferometric modulator (IMOD) displays. She also investigates novel materials to improve reliability and processing of IMOD.
Katherine Whittaker Ferrara is an American engineer who is a professor of radiology at Stanford University. Ferrara has been elected a Fellow of the American Association for the Advancement of Science, Institute of Electrical and Electronics Engineers and American Institute for Medical and Biological Engineering.
Dragan Damjanovic is a Swiss-Bosnian-Herzegovinian materials scientist. From 2008 to 2022, he was a professor of material sciences at EPFL and head of the Group for Ferroelectrics and Functional Oxides.
