Piezoelectric bimorphs

Flgnre 16.1 Bimorph piezoelectric cantilever under base excitation (Elvin and Erturk, 2013) (Reproduced with permission). 

To measure friction and shear response, one has to laterally drive one surface and simultaneously measure the response of a lateral spring mount. A variety of versions have been devised. Lateral drives are often based on piezoelectric or bimorph deflection [13, 71] or DC motor drives, whereas the response can be measured via strain gauges, bimorphs, capacitive or optical detection. 

In Part II, we discuss the essential elements of STM instrumentation. Except for a few cross-references, all the chapters can be read independently. The chapter on piezodrives starts with an introduction to piezoelectricity and piezoelectric ceramics at the general physics level. Three major types of piezodrives, the tripod, the bimorph, and the tube, are analyzed in detail. The chapter on vibration isolation starts with general concepts and vibration meas-... 

If larger displacements are required, an arrangement as shown in Fig. 9.7, the bimorph, can be applied. The principle is similar to the bimetal thermometer. Two thin plates of piezoelectric material are glued together. By applying a voltage, one plate expands and the other one contracts. The composite flexes. 

Fig. 9.8. Deflection of a bimorph. Two long, thin plates of piezoelectric material are glued together, with a metal film sandwiched in between. Two more metal films cover the outer surfaces. Both piezoelectric plates are poled along the same direction, perpendicular to the large surface, labeled z. (A) By applying a voltage, stress of opposite sign is developed in both plates, which generates a torque. (B) The bimorph flexes to generate a stress to compensate the torque. The neutral plane, where the stress is zero, lies at hi i from the central plane.

Piezoelectric Disk a) Piezoelectric Bimorph (Disk Type) (a) Ring Mesa (Bulk Si 8nl/min (100V,lHz) l.OmHjO... 

C.J. Morris and F.K. Forster, Optimization of a circular piezoelectric bimorph for a micropump driver, J. Micromech. Microeng., 10 (2000) 459-465. 

These companies can supply piezoelectric material and devices such as tubes, stacked assemblies, unimorphs, and bimorphs. 

The MASIF (measurements and analysis of surface interaction and forces) force measuring device is based on a bimorph force sensor [47]. The bimorph consists of two piezoelectric plates glued together with opposing... 

To confirm that the results from d33 and remanent polarization measurements translate into bimorph performance across a wide temperature range, small rectangular bimorphs were fabricated to mimic small sections of a thin film telescope mirror. An electric field was applied to the bimorphs and the maximum deflection measured. This deflection was converted to d31 (the piezoelectric response in the plane parallel to the deflection) 12) and plotted (Figure 3) between -95 and +80°C. Superimposed on the plots are the moduli of... 

The first commercial piezoelectric BaTiOs devices were phonograph pickups marketed by Sonotome Corporation in the mid-1940s. These used a so-called bimorph design in which an electrode layer separated two strips of the piezoelectric material. Bimorphs are no longer used for this application because they do not produce a high enough quality sound reproduction and most people use CDs now. 

Despite the new insights achieved with the SFA, there are also severe problems and limits. It is difficult and slow to operate, only mica and few other materials [42, 43] provide suitable substrates, elastic deformation has to be taken into account. With the invention of a bimorph surface force apparatus, known as MAS IF, some of these Kmitations could be overcome [44, 45]. In this case the force between two glass or polymer spheres of typically few millimeter diameter is measured. One sphere is therefore attached to a piezoelectric bimorph that serves as a force sensor. 

The force as a function of surface separation between glass substrate surfaces was measured with a MASIF instrument [28], This apparatus is based on a bimorph force sensor to which one of the surfaces is mounted (Fig. 5). The other surface is mounted on a piezoelectric tube. The bimorph (enclosed in a Teflon sheath) is mounted inside a small measiuing chamber, which is clamped to a translation stage that serves to control the coarse position of the piezoelectric tube and the upper siuface. 

Furthermore, monolayer measurements demonstrate the variation of the dipole moment of peripheral proteins under stretching or compression. According to us, this implies the possibility of bimorph flexoelectricity of peripheral proteins (an analogue of the piezoelectricity of a bimorph plate), especially if these are symmetrically adsorbed over the two membrane interfaces, as suggested in the Danielli-Davson model. ... 

A structure composed of two active layers and one or more passive layers. Typically the active layers work through either thermal expansion, hygrothermal expansion, or piezoelectric expansion via an externally applied electrical field. Bimorphs are used in the latter case to amplify... 

Piezoelectric Actuation in Multiphase Microfluidics, Fig. 1 (a) Schematics of a microfluidic chip for drop-on-demand dispensing. The bottom chamber is filled with an aqueous reagent A piezoelectric bimorph actuator glued to the chamber allows the release of an aqueous drop on demand in the horizontal channel filled with an immiscible fiuid. (b) Description of the experimental setup. The... 

Lu, P. and Lee, K. (2003). An alternative derivation of dynamic admittance matrix of piezoelectric cantilever bimorph. Journal of Sound and Vibration 266, pp. 723-735. 

Piezoelectric scanners Piezoelectrics are materials whose dimensions deform in response to an applied electric field. If the voltages that are applied to a piezoelectric are precisely controlled, extremely precise movements can be performed. The geometry of piezoelectric positioning devices used in STM includes bars, bimorphs, or tubes tubular scanners are the most commonly used. They operate at a high resonant frequency, enabling high scan rates. Thermal isolation of the piezoelectric elements is necessary since these ceramics are also sensitive to... 

The use of deformable mirrors to compensate the aberration of astronomical images caused by the turbulence of the earth atmosphere has led to outstanding successes of ground-based astronomy. In collaboration with the Active Structures Laboratory of Bmssels University a demonstrator for a bimorph mirror was developed and manufactured as shown in Fig. 12 It consists of a silicon wafer with a diameter of 150 mm and 0,75 mm thickness as well as 91 honeycomb thick film piezoelectric actuators with 80 pm thickness, which have been screen printed at the backside of the silicon wafer. Each actuator can be driven individually to control the shape of the bimorph mirror and thus optical aberrations. 

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