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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'.
In electromagnetism, a dielectric is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, because they have no loosely bound, or free, electrons that may drift through the material, but instead they shift, only slightly, from their average equilibrium positions, causing dielectric polarisation. Because of dielectric polarisation, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarised, but also reorient so that their symmetry axes align to the field.
In physics, the term dielectric strength has the following meanings:
Pyroelectricity is a property of certain crystals which are naturally electrically polarized and as a result contain large electric fields. Pyroelectricity can be described as the ability of certain materials to generate a temporary voltage when they are heated or cooled. The change in temperature modifies the positions of the atoms slightly within the crystal structure, so that the polarization of the material changes. This polarization change gives rise to a voltage across the crystal. If the temperature stays constant at its new value, the pyroelectric voltage gradually disappears due to leakage current. The leakage can be due to electrons moving through the crystal, ions moving through the air, or current leaking through a voltmeter attached across the crystal.
Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride. Its chemical formula is (C2H2F2)n.
An electret is a dielectric material that has a quasi-permanent electric charge or dipole polarisation. An electret generates internal and external electric fields, and is the electrostatic equivalent of a permanent magnet. Although Oliver Heaviside coined this term in 1885, materials with electret properties were already known to science and had been studied since the early 1700s. One particular example is the electrophorus, a device consisting of a slab with electret properties and a separate metal plate. The electrophorus was originally invented by Johan Carl Wilcke in Sweden and again by Alessandro Volta in Italy.
Lead zirconate titanate, also called lead zirconium titanate and commonly abbreviated as PZT, is an inorganic compound with the chemical formula Pb[ZrxTi1−x]O3(0 ≤ x ≤ 1). It is a ceramic perovskite material that shows a marked piezoelectric effect, meaning that the compound changes shape when an electric field is applied. It is used in a number of practical applications such as ultrasonic transducers and piezoelectric resonators. It is a white to off-white solid.
An electroactive polymer (EAP) is a polymer that exhibits a change in size or shape when stimulated by an electric field. The most common applications of this type of material are in actuators and sensors. A typical characteristic property of an EAP is that they will undergo a large amount of deformation while sustaining large forces.
Gerhard M. Sessler is a German inventor and scientist. He is Professor emeritus at the Department of Electrical Engineering and Information Technology of the Technische Universität Darmstadt.
An electret microphone is a type of electrostatic capacitor-based microphone, which eliminates the need for a polarizing power supply by using a permanently charged material.
Ferroelectric polymers are a group of crystalline polar polymers that are also ferroelectric, meaning that they maintain a permanent electric polarization that can be reversed, or switched, in an external electric field.
Piezoelectric Micromachined Ultrasonic Transducers (PMUT) are MEMS-based piezoelectric ultrasonic transducers. Unlike bulk piezoelectric transducers which use the thickness-mode motion of a plate of piezoelectric ceramic such as PZT or single-crystal PMN-PT, PMUT are based on the flexural motion of a thin membrane coupled with a thin piezoelectric film, such as PVDF. In comparison with bulk piezoelectric ultrasound transducers, PMUT can offer advantages such as increased bandwidth, flexible geometries, natural acoustic impedance match with water, reduced voltage requirements, mixing of different resonant frequencies and potential for integration with supporting electronic circuits especially for miniaturized high frequency applications.
Gordon Eugene Martin is an American physicist and author in the field of piezoelectric materials for underwater sound transducers. He wrote early computer software automating iterative evaluation of direct computer models through a Jacobian matrix of complex numbers. His software enabled the Navy Electronics Laboratory (NEL) to accelerate design of sonar arrays for tracking Soviet Navy submarines during the Cold War.
A complex oxide is a chemical compound that contains oxygen and at least two other elements. Complex oxide materials are notable for their wide range of magnetic and electronic properties, such as ferromagnetism, ferroelectricity, and high-temperature superconductivity. These properties often come from their strongly correlated electrons in d or f orbitals.
Reimund Gerhard is a German applied physicist and university professor. Between 1979 and 2006 he used the last name "Gerhard-Multhaupt".
Soft robotics is a subfield of robotics that concerns the design, control, and fabrication of robots composed of compliant materials, instead of rigid links. In contrast to rigid-bodied robots built from metals, ceramics and hard plastics, the compliance of soft robots can improve their safety when working in close contact with humans.
Kenji Uchino is an American electronics engineer, physicist, academic, inventor and industry executive. He is currently a professor of Electrical Engineering at Pennsylvania State University, where he also directs the International Center for Actuators and Transducers at Materials Research Institute. He is the former associate director at The US Office of Naval Research – Global Tokyo Office.
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.
Cumyl alcohol, also called 4-isopropylbenzyl alcohol, is a liquid, hydroxy functional, aromatic organic chemical with formula C10H14O. It has the CAS Registry Number of 536-60-7 and the IUPAC name of (4-propan-2-ylphenyl)methanol. It is REACH registered with the EC number of 208-640-4.
References
- Gerhard-Multhaupt, R. (2002). "Less can be more. Holes in polymers lead to a new paradigm of piezoelectric materials for electret transducers". IEEE Transactions on Dielectrics and Electrical Insulation . 9 (5): 850–859. doi:10.1109/TDEI.2002.1038668. ISSN 1070-9878.
- Bauer, Siegfried; Gerhard-Multhaupt, Reimund; Sessler, Gerhard M. (2004). "Ferroelectrets: Soft Electroactive Foams for Transducers". Physics Today. 57 (2): 37–43. Bibcode:2004PhT....57b..37B. doi:10.1063/1.1688068. ISSN 0031-9228.
- Wegener, Michael; Bauer, Siegfried (2005). "Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles". ChemPhysChem. 6 (6): 1014–1025. doi:10.1002/cphc.200400517. ISSN 1439-4235. PMID 15887192.
- Bauer, S. (2006). "Piezo-, pyro- and ferro-electrets: Soft transducer materials for electromechanical energy conversion". IEEE Transactions on Dielectrics and Electrical Insulation . 13 (5): 953–962. doi:10.1109/TDEI.2006.247819. S2CID 34332152.