MDE-Seminar-SmartMaterials.

=A.Shape Memory Alloys. = Shape Memory Alloys (SMA) are materials that remember their original shape, this great property makes the material usable in many applications and forms. One way of using this material is in the form of an actuator, which is a material that has one or more of its mechanical properties change with the application of heat or magnetic fields. (1).  media type="youtube" key="aynp7utEXdQ" height="315" width="560" align="center"

1. History of the Material.
Although the effect and property of the SMA was first noticed in the 1930s, it wasn't until the 1960s that the SMA was developed and produced in the form of Nickel-Titanium Alloys in the United States Naval Ordnance Laboratory, which was later commercialized under the name Nitinol which is an acronym for Nickel Titanum Naval Ordnance Laboratories. (2) There is another SMA known as FSMA (Ferromagnetic Shape Memory Alloy), which reacts to high magnetic fields, these materials are a bit better than the previous mentioned materials, because the reaction time to magnetic fields is a lot faster than to temperature change. (2)

2. Properties.
Most SMA including Nickel-Titanium alloys are considered to be engineering materials, which can be manufactured in almost every shape and size. The yield strength of SMA is lower than that of Steel, and that of NiTi is equal to 500 MPa. Another property is their high level of recoverable plastic strain that can be induced, the maximum value of recoverable strain that these materials can withstand is about 8% which is very high in comparison to the 0.5% of that of steel.

3.Applications.
(3)
 * Aircraft.
 * Automotive.
 * Dentistry.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Medicine.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Piping.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Robotics.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Telecommunication.

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<span style="font-family: Arial,Helvetica,sans-serif;">4.References.
<span style="font-family: Arial,Helvetica,sans-serif;">- <span class="wiki_link_ext">http://www.stanford.edu/~richlin1/sma/sma.html <span style="font-family: Arial,Helvetica,sans-serif;">- <span class="wiki_link_ext">http://www.smaterial.com/SMA/sma.html <span style="font-family: Arial,Helvetica,sans-serif;">(1) Rogers, Craig. "Intelligent Materials." Scientific American Sept. 1995: 154-157. <span style="font-family: Arial,Helvetica,sans-serif;">(2) Kauffman, George, and Isaac Mayo. "Memory Metal." Chem Matters Oct. 1993. <span style="font-family: Arial,Helvetica,sans-serif;">(3) Chen, H. R. (2010). Shape Memory Alloys: Manufacture, Properties and Applications. Nova Science Pub Inc.

=<span style="font-family: Arial,Helvetica,sans-serif;">B. Magnetorheological Fluids. =

1. History.
<span style="display: block; font-family: Arial,sans-serif; font-size: 10pt; text-align: left;">Magnetorheological fluids wre first invented in 1949s by the inventor Jacob RabinowA laboratory curiosity with little practical use for decades, researchers began to get serious about it in the late 1980s and 1990s, when other technologies began to converge that made practical use of MR fluid a real possibility. <span style="display: block; font-family: Arial,sans-serif; font-size: 10pt; text-align: left;"> Still, new technologies aside, moving this new material from lab to commercialization faced huge hurdles. Cary, N.C.-based Lord Corporation holds the world’s most extensive patent portfolio on MR fluid formulations. Lord engineers invented their own MR devices to demonstrate how the material functioned and how it would look in a real application.

2.Properties.
<span style="display: block; font-family: Arial,sans-serif; font-size: 10pt; text-align: left;">The need of a controlled viscoelastic solid was finally achieved after the discovery of the Magnetorheological Fluids .viscose materials such as honey, resist <span class="wiki_link_ext">shear flow and <span class="wiki_link_ext">strain  linearly with time when a <span class="wiki_link_ext">stress  is applied. Elastic materials strain instantaneously when stress is applied and just as quickly return to their original state once the stress is removed. As a result of the vescoelastic property the Magnetorheological Fluids have the ability to creep, recover, undergo stress relaxation and absorb energy. These properties will be discus in the MRfluids applications. fig 2.1shows the Stress-Strain Curves for a purely elastic material (a) and a viscoelastic material (b).
 * 2.1. Viscoelasticity.**

<span style="font-family: Arial,sans-serif; font-size: 10pt;">The variation of magnetic field intensity affects the yield stress of the fluid. upshot of this is that the fluid's ability to transmit force can be controlled with an electromagnet, which gives rise to its many possible control-based applications.
 * 2.2. Yield Stress.**

<span style="display: block; font-family: Arial,sans-serif; font-size: 10pt; text-align: left;">Low shear stress has been the primary reason for limited range of applications. In the absence of external pressure the maximum shear strength is about 100 kPa. If the fluid is compressed in the magnetic field direction and the compressive stress is 2 MPa, the shear strength is raised to 1100 kPa. If the standard magnetic particles are replaced with elongated magnetic particles, the shear is also improved.(1)
 * 2.3.Shear Stress.**

** 3.MF Composition. **

<span style="font-family: Arial,sans-serif; font-size: 10pt;">Magnetorheological fluid is composed of three ingredients: carbonyl iron particles, 'soft' iron particles which are only 3-5 micrometers in diameter (or 0.0003 to 0.0005 millimeters); a 'carrier' liquid, usually hydrocarbon oil; and additives which enhance lubricity, modifies the fluid's thickness or viscosity, keeps the particles suspended in the liquid, and slows down the gravitational setting of the iron particles.

<span style="font-family: Arial,sans-serif; font-size: 10pt;">The carbonyl iron particles provide the means for changing the fluid into solid; applying a magnetic field to the Magnetorheological fluid forces the particles to line up so the liquid becomes solid. The solidity of the fluid is influenced by the strength of the magnetic field – the stronger the field, the 'harder' the Magnetorheological fluid becomes. Removing the magnetic field unlocks the particles and turns the solid back to liquid

4.How MR Fluid Works.
<span style="font-family: Arial,sans-serif; font-size: 10pt;">The carbonyl iron particles provide the means for changing the fluid into solid; applying a magnetic field to the Magnetorheological fluid forces the particles to line up so the liquid becomes solid. The solidity of the fluid is influenced by the strength of the magnetic field – the stronger the field, the 'harder' the Magnetorheological fluid becomes. Removing the magnetic field unlocks the particles and turns the solid back to liqui

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<span style="font-family: Arial,sans-serif;">5.Applications.
<span style="font-family: Arial,sans-serif; font-size: 10pt;">Mechanically, mainly Magnetorheological Fluids are used as mechanical dampers for heavy motors and machines. As they absorb energy that generate vibrations and shocks. Even in building constraction,it absorbing detrimental shock waves and oscillations within the structure, giving these dampers the ability to make any building earthquake-proof, or at least earthquake-resistant.also it was used in MR Damper Seat Suspension Applications.

<span style="display: block; font-family: Arial,sans-serif; font-size: 10pt; text-align: left;">Militarily, The U.S. Army Research Office is currently funding research into using MR fluid to enhance body armor. In 2003, researchers stated they were five to ten years away from making the fluid bullet resistant. In addition, Humvees, and various other all-terrain vehicles employ dynamic MR shock absorbers and/or dampers. Magnetorheological dampers are under development for use in military and commercial helicopter cockpit seats, as safety devices in the event of a crash. They would be used to decrease the shock delivered to a passenger's spinal column, thereby decreasing the rate of permanent injury during a crash.

<span style="font-family: Arial,sans-serif;">References.
<span style="font-family: Arial,sans-serif;">- <span style="font-family: Arial,sans-serif; font-size: 10pt;">http://en.wikipedia.org/wiki/Magnetorheological_fluids <span style="font-family: Arial,sans-serif; font-size: 10pt;">-http://www.materiatech-carma.net <span style="font-family: Arial,sans-serif; font-size: 10pt;">-J.S. Chong, E.B. Christiansen, A.D. Baer, Rheology of Concentrated Suspensions, Journal of Applied Polymer Science 15 (1971) 2007-2021. <span style="font-family: Arial,sans-serif;">-(1) <span style="font-family: Arial,sans-serif; font-size: 10pt;">["Physical Properties of Elongated Magnetic Particles" by Fernando Vereda, Juan de Vicente, Roque Hidalgo-Álvarez]

=<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif;">C.Ionic Polymer Composites. =

<span style="font-family: Arial,Helvetica,sans-serif;">1. History
<span style="font-family: Arial,sans-serif; font-size: 10pt;">The field of ionic polymer composites began in 1880; the start was when Wilhelm Roentgen made an experiment on the effect of an electrical current on the mechanical properties of a rubber band. The rubber band was attached to a mass and fixed from the other side with an electrical current. In 1899 Sacerdote followed up on Roentgen’s experiment by studying the strain response to an electric field. In 1925 the first piezoelectric material was discovered. It was called Electrets. It was formed by "combining carnauba wax, rosin and beeswax, and then cooling the solution while it is subject to an applied DC electrical bias". This combination can be solidified into a polymer form that can be treated as a piezoelectric material. (Cohen, 2004) <span style="font-family: Arial,sans-serif; font-size: 10pt;"> Polymers that respond to environmental conditions other than an applied electrical current have also been a large part of this area of study. In 1949, Katchalsky et al. demonstrated that when collagen filaments are dipped in acid or alkali solutions they would respond with a change in volume. (Cohen, 2004) <span style="font-family: Arial,sans-serif; font-size: 10pt;">In 1990s, ionic polymer-metal composites were developed with electro- active properties far superior to previous EAPs. The major advantage of IPMCs was that they were able to show activation at voltages as low as 1 or 2 volts. In 1999, a specialist in the field of robotics and artificial muscles, Yoseph Bar-Cohen, proposed the Arm wrestling Match of EAP Robotic Arm against Human Challenge. This was a challenge in which research groups around the world competed to design a robotic arm consisting of EAP muscles that could defeat a human in an arm wrestling match. The first challenge was held at the Electro active Polymer Actuators and Devices Conference in 2005. Another major milestone of the field is that the first commercially developed device including EAPs as an artificial muscle was produced in 2002 by Eames in Japan. This device was a fish that is able to swim on its own, moving its tail using an EAP muscle. But the progress in practical development is not satisfactory, probably due to misleading in fundamental research. (Cohen, 2004)

<span style="font-family: Arial,sans-serif;">2. Introduction.
<span style="font-family: Arial,sans-serif; font-size: 10pt;"> An ionic polymer metal composite (IPMC) is a “thin ionomeric membrane with noble metal electrodes plated on both its surfaces, and is neutralized with a certain amount of cations that balance the electrical charge of the anions covalently fixed to the backbone membrane”. An ionic polymer-metal composite (IPMC) consisting of a thin per fluorinated ionomer strip, platinum, and sometimes it is gold plated on each sides and neutralized by an amount of proper captions that undergoes large bending motion when, in a hydrated state, we apply an electric current across its thickness. “When the same membrane is suddenly bent, a small voltage of the order of mill volts is produced across its surfaces. Hence IPMCs can serve as soft bending actuators and sensors”. This response of IPMCs relies on the ionic polymer crystal structure, the electrode conductivity and morphology, and the hydration level, and finally the captions nature. Extensive experimentations on both Nafion- and Flemion-based IPMCs in various action forms were carried out seeking to understand these composites characteristics, to optimize their performance for several industrial applications, and finally to explore their actuation mechanism. “The results of these tests on both Nafion- and Flemion-based IPMCs with alkali-metal or alkyl-ammonium captions are reported here. Compared with Nafion-based IPMCs, Flemion-based IPMCs with fine dendritic gold electrodes have higher ion-exchange capacity, better surface conductivity, higher hydration capacity and higher longitudinal stiffness. They also display greater bending actuation under the same applied voltage. In addition, they do not display a reverse relaxation under a sustained DC voltage, which is typical of Nafion-based IPMCs in alkali-metal form. Flemion IPMCs thus are promising composites for application as bending actuators”. (Wu, 2003)

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<span style="font-family: Arial,sans-serif;">3. Applications.
<span style="font-family: Arial,sans-serif; font-size: 10pt;">The electro-mechanical response of an IPMC depends on its monomer, electrodes’ morphology, counter ion, and its degree of hydration. Flexion monomers with carboxyl ate side groups have higher ion exchange capacity, higher stiffness, and greater water uptake than Nation monomers. In Pt/Au plated Nation-based IPMCs, platinum particles deeply diffuse into the perfluorosulfonic membrane. The electrodes in Au plated Flemion-based IPMCs have a fine dendritic structure with high interfacial area, ideal for enhancing the IPMC’s actuation through better surface conductivity. (Wu, 2003)



<span style="font-family: Arial,sans-serif; font-size: 10pt;"> The axial elongation stiffness of bare ionomers and IPMCs is measured and presented in terms of the Young modulus. The results are used to estimate the bending stiffness of the IPMC. Our study shows that the stiffness of the bare ionomer and the IPMC is strongly affected by their hydration level. A dry sample may have stiffness 10 times greater than when it is water saturated. In addition, the nature of the neutralizing caption has a significant effect on the stiffness. Generally, for a same membrane at the same hydration level, the stiffness increases with increasing formula weight of the caption. The axial stiffness is measured using the mini-load frame shown in the figure in the margin. In open air, the hydration level of both dry- and wet form samples does not remain constant. Samples in dry form absorb moisture, whereas samples in wet form lose. (Wu, 2003)
 * <span style="font-family: Arial,sans-serif;"> 3.1. Stiffness Versus Hydration. **



<span style="font-family: Arial,sans-serif; font-size: 10pt;">Surface conductivity is a major electrical property governing an IPMC’s actuation behavior. When applying a potential across the sample’s thickness at the grip-end, the bending of the cantilever is affected by its surface resistance, which in turn is dependent on the electrode morphology, caption form, and the level of hydration. A device with four platinum probes is developed to measure the IPMC’s surface resistance. See the figure below. The voltage drop between the two inner probes and the current through the two outer probes are measured in order to calculate the IPMC’s surface resistance (Wu, 2003)
 * <span style="font-family: Arial,sans-serif; font-size: 10pt;"> 3.2. Surface Conductivity. **



<span style="font-family: Arial,sans-serif;">4.References.
<span style="font-family: Arial,sans-serif;">- <span style="font-family: Arial,sans-serif; font-size: 10pt;">Wu, S. N.-N. (2003). Comparative experimental study of ionic polymer-metal composites. //<span style="font-family: Arial,sans-serif; font-size: 10pt;">JOURNAL OF APPLIED PHYSICS, Vol. 93, No. 9. //<span style="font-family: Arial,sans-serif; font-size: 10pt;">, 5255-5267. <span style="font-family: Arial,sans-serif; font-size: 10pt;">-Yoseph Bar-Cohen, 2004, lElectrochemistry Encyclopedia: Electro active Polymers (EAP)". Retrieved from http://electrochem.cwru.edu/encycl/art-p02-elact-pol.htm. On 28/2/2012

Is the charge that accumulates in certain solid materials in response to applied mechanical <span class="wiki_link_ext">stress. The word //piezoelectricity// means electricity resulting from pressure. The <span class="wiki_link_ext">piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials. The piezoelectric effect is a <span class="wiki_link_ext">reversible process in that materials exhibiting the direct piezoelectric effect (the internal generation of electrical charge resulting from an applied mechanical <span class="wiki_link_ext">force ) also exhibit the reverse piezoelectric effect (the internal generation of a mechanical strain resulting from an applied electrical field). Piezoelectricity is found in useful applications such as the production and detection of sound, generation of high voltages, electronic frequency generation, <span class="wiki_link_ext">microbalances, and ultrafine focusing of optical assemblies. It is also the basis of a number of scientific instrumental techniques with atomic resolution, the <span class="wiki_link_ext">scanning probe microscopes such as <span class="wiki_link_ext">STM, <span class="wiki_link_ext">AFM , <span class="wiki_link_ext">MTA , <span class="wiki_link_ext">SNOM , etc., and everyday uses such as acting as the ignition source for <span class="wiki_link_ext">cigarette lighters and push-start <span class="wiki_link_ext">propane barbecues. Gautschi, G (2002). //Piezoelectric Sensorics: Force, Strain, Pressure, Acceleration and Acoustic Emission Sensors, Materials and Amplifiers.//. Springer.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 18.6667px;">D.Piezoelectric materials: **
 * <span style="font-family: 'Times New Roman','serif'; font-size: 18.6667px;">D.1-__Introduction: (abstract):__ **
 * <span style="font-family: 'Times New Roman','serif'; font-size: 18.6667px;">D.2-__Discovery and early research:__ **

The <span class="wiki_link_ext">pyroelectric effect, by which a material generates an electric potential in response to a temperature change, was studied by <span class="wiki_link_ext">Carl Linnaeus and <span class="wiki_link_ext">Franz Aepinus in the mid-18th century. Drawing on this knowledge, both <span class="wiki_link_ext">René Just Haüy and <span class="wiki_link_ext">Antoine César Becquerel posited a relationship between mechanical stress and electric charge. The first demonstration of the direct piezoelectric effect was in 1880 by the brothers <span class="wiki_link_ext">Pierre Curie and <span class="wiki_link_ext">Jacques Curie. They combined their knowledge of pyroelectricity with their understanding of the underlying crystal structures that gave rise to pyroelectricity to predict crystal behavior, and demonstrated the effect using crystals of <span class="wiki_link_ext">tourmaline, <span class="wiki_link_ext">quartz , <span class="wiki_link_ext">topaz , <span class="wiki_link_ext">canesugar , and <span class="wiki_link_ext">Rochelle salt (sodium potassium tartrate tetrahydrate). Quartz and Rochelle salt exhibited the most piezoelectricity.

For the next few decades, piezoelectricity remained something of a laboratory curiosity. More work was done to explore and define the crystal structures that exhibited piezoelectricity. Lippman, G. (1881). <span class="wiki_link_ext">"Principe de la conservation de l'électricité" (in French). <span class="wiki_link_ext">//Annales de chimie et de physique// **24**: 145.

5.3-__Mechanism:__
The nature of the piezoelectric effect is closely related to the occurrence of <span class="wiki_link_ext">electric dipole moments in solids. The latter may either be induced for <span class="wiki_link_ext">ions on <span class="wiki_link_ext">crystal lattice sites with asymmetric charge surroundings (as in <span class="wiki_link_ext">BaTiO3 and <span class="wiki_link_ext">PZTs ) or may directly be carried by molecular groups (as in <span class="wiki_link_ext">cane sugar ). Dipoles near each other tend to be aligned in regions called <span class="wiki_link_ext">Weiss domains. The domains are usually randomly oriented, but can be aligned using the process of //poling// (not the same as <span class="wiki_link_ext">magnetic poling ), a process by which a strong electric field is applied across the material, usually at elevated temperatures. Not all piezoelectric materials can be poled.

Of decisive importance for the piezoelectric effect is the change of polarization **//P//** when applying a <span class="wiki_link_ext">mechanical stress. This might either be caused by a re-configuration of the dipole-inducing surrounding or by re-orientation of molecular dipole moments under the influence of the external stress. Piezoelectricity may then manifest in a variation of the polarization strength, its direction or both, with the details depending on: 1. the orientation of **//P//** within the crystal, 2. <span class="wiki_link_ext">crystal symmetry and 3. the applied mechanical stress. The change in **//P//** appears as a variation of surface <span class="wiki_link_ext">charge density upon the crystal faces. S. Trolier-McKinstry (2008). "Chapter3: Crystal Chemistry of Piezoelectric Materials". In A. Safari, E.K. Akdo˘gan. //Piezoelectric and Acoustic Materials for Transducer Applications//. New York: Springer. <span class="wiki_link_ext">ISBN 9780387765389.
 * 5.4-__These are some videos about the piezoelectric effect:__ **

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Quartz Topaz Sucrose
 * 5.5-__Examples of some piezoelectric materials:__ **
 * <span style="font-family: 'Times New Roman','serif'; font-size: 18px;">Naturally occurring crystals **
 * <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">Berlinite <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> (AlPO <span style="font-family: 'Times New Roman','serif'; font-size: 13.3333px;">4 <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">), a rare <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">phosphatemineral  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> that is structurally identical to quartz.
 * <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">Sucrose <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> (table sugar).
 * <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">Quartz <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">.
 * <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">Rochelle salt <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">.
 * <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">Topaz <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">.
 * <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">Tourmaline-group minerals <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">.

5.6.1-Surgery:
A recent application of piezoelectric ultrasound sources is piezoelectric surgery, also known as <span class="wiki_link_ext">piezosurgery. Piezosurgery is a minimally invasive technique that aims to cut a target tissue with little damage to neighboring tissues. For example, Hoigne et al.Reported its use in hand surgery for the cutting of bone, using frequencies in the range 25–29 kHz, causing microvibrations of 60–210 μm. It has the ability to cut mineralized tissue without cutting neurovascular tissue and other soft tissue, thereby maintaining a blood-free operating area, better visibility and greater precision. Manbachi, A. and Cobbold R.S.C. (November 2011). <span class="wiki_link_ext">"Development and Application of Piezoelectric Materials for Ultrasound Generation and Detection". //Ultrasound// **19** (4): 187–196. <span class="wiki_link_ext">doi : <span class="wiki_link_ext">10.1258/ult.2011.011027.

5.6.2-Infertility treatment:
In people with previous <span class="wiki_link_ext">total fertilization failure, piezoelectric activation of oocytes together with <span class="wiki_link_ext">intracytoplasmic sperm injection (ICSI) seems to improve fertilization outcome.

5.6.3-Reduction of vibrations and noise:
Different teams of researchers have been investigating ways to reduce vibrations in materials by attaching piezo elements to the material. When the material is bent by a vibration in one direction, the vibration-reduction system responds to the bend and sends electric power to the piezo element to bend in the other direction. Future applications of this technology are expected in cars and houses to reduce noise. In a demonstration at the Material Vision Fair in <span class="wiki_link_ext">Frankfurt in November 2005, a team from <span class="wiki_link_ext">TU Darmstadt in <span class="wiki_link_ext">Germany showed several panels that were hit with a rubber mallet, and the panel with the piezo element immediately stopped swinging. Piezoelectric ceramic fiber technology is being used as an electronic damping system on some <span class="wiki_link_ext">HEADtennis rackets. <span class="wiki_link_ext">"Isn’t it amazing how one smart idea, one chip and an intelligent material has changed the world of tennis?" . HEAD. Retrieved 2008-02-27.

<span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">The piezo-electrical properties of quartz are useful as <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">standard of frequency <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px;">.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">5.6.4-Frequency standard: **
 * <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">Quartz clocks <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> employ a <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">crystal oscillator  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> made from a quartz crystal that uses a combination of both direct and converse piezoelectricity to generate a regularly timed series of electrical pulses that is used to mark time. The quartz crystal (like any <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">elastic  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> material) has a precisely defined natural frequency (caused by its shape and size) at which it prefers to <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">oscillate  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">, and this is used to stabilize the frequency of a periodic voltage applied to the crystal.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">The same principle is critical in all <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">radiotransmitters <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> and <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">receivers  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">, and in <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">computers  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> where it creates a <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">clock pulse  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">. Both of these usually use a <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">frequency multiplier  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> to reach gigahertz ranges.

<span style="font-family: 'Times New Roman','serif'; font-size: 16px;">A slip-stick actuator. <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Types of piezoelectric motor include: <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">All these motors, except the stepping stick-slip motor work on the same principle. Driven by dual orthogonal vibration modes with a <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">phase <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> difference of 90°, the contact point between two surfaces vibrates in an <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">elliptical  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> path, producing a <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">frictional  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> force between the surfaces. Usually, one surface is fixed causing the other to move. In most piezoelectric motors the piezoelectric crystal is excited by a <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">sine wave <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> signal at the resonant frequency of the motor. Using the resonance effect, a much lower voltage can be used to produce a high vibration amplitude. <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Stick-slip motor works using the inertia of a mass and the friction of a clamp. Such motors can be very small. Some are used for camera sensor displacement, allowing anti shake function.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 18px;">5.6.5-Piezoelectric motors: **
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">The <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">traveling-wave motor <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> used for <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">auto-focus  <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> in <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">reflex cameras
 * <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">Inchworm motors <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> for linear motion
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Rectangular four-quadrant motors with high power density (2.5 <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">watt <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">/cm3) and speed ranging from 10 nm/s to 800 mm/s.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 16px;">Stepping piezo motor, using <span style="color: #000000; font-family: 'Times New Roman','serif'; font-size: 16px; text-decoration: none;"><span class="wiki_link_ext">stick-slip <span style="font-family: 'Times New Roman','serif'; font-size: 16px;"> effect.


 * Many other applications such as: **

5.6.7-High voltage and power sources

 * 5.6.8-Sensors **

__**Refrences:**__ Gautschi, G (2002). //Piezoelectric Sensorics: Force, Strain, Pressure, Acceleration and Acoustic Emission Sensors, Materials and Amplifiers.//. Springer. Lippman, G. (1881). <span class="wiki_link_ext">"Principe de la conservation de l'électricité" (in French). <span class="wiki_link_ext">//Annales de chimie et de physique// **24**: 145. "Chapter3: Crystal Chemistry of Piezoelectric Materials". In A. Safari, E.K. Akdo˘gan. //Piezoelectric and Acoustic Materials for Transducer Applications//. New York: Springer. <span class="wiki_link_ext">ISBN 9780387765389. Manbachi, A. and Cobbold R.S.C. (November 2011). <span class="wiki_link_ext">"Development and Application of Piezoelectric Materials for Ultrasound Generation and Detection". //Ultrasound// **19** (4): 187–196. <span class="wiki_link_ext">doi : <span class="wiki_link_ext">10.1258/ult.2011.011027.

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