Actuators, piezoelectric

Barrow, D. A. Noteboom, R. Sayer, M. 1995. Design and fabrication of macroscopic piezoelectric actuators based on thick PZT films. Int. Ferro. 8 1-11. 

Percin, G. Levin, L. Khuri-Yakub, B. 1997. Piezoelectrically actuated droplet ejector. Rev. Sci. Instr. 68 4561—4563. 

Piezochromism, 6 606-607, 612-613 negative piezosolvatochromism, 6 611 Piezoelectric actuation, for lab-on-a-chip valves, 26 975... 

Ayhan, A.E. 2002. Design of a piezoelectrically actuated microvalve for flow control in fuel cells. M.S. Thesis, University of Pittsburgh, School of Engineering, Pittsburgh, PA. 

Fig. 6. Principle of check-valve micropump with piezoelectric actuation...

A piezoelectric pump is constructed with two glass plates and a silicon wafer [22]. A pressure chamber and a raised flat surface suspended with a thin diaphragm are formed on the upper glass plate (Fig. 3). The piezoelectric actuator is placed on the raised flat surface. In order to guide the flow of the pumped liquid, two check valves made of poly-silicon are fabricated on the silicon wafer... 

Pressure-driven liquid flow can also be achieved by a piezoelectric actuator and a pivoted lever for linear displacement amplification (nine-fold) on a PMM A chip. Flow rate of 1 nL/min has been attained [380]. 

Other micromixers based on various principles have also been constructed. These principles include vortex [492], eddy diffusion [493-501,654,955], rotary stirring [502], turbulence [495,503], EK instability [504—506], chaotic advection [248,507-513], magnetic stirring [514], bubble-induced acoustic mixing [515], and piezoelectric actuation [516,517]. 

Uchino, K. (1997) Piezoelectric Actuators and Ultrasonic Motors, Kluwer Academic Publishers, London. 

FIG. 1 Schematic representation of the tracking device. The piezoelectric actuator, which keeps the focali/alion constant and allows one to access the third dimension of the motion, can be mounted either on the cell (a) or on the objective (b). 

Since the introduction of the STM a number of variations have been devised, such as ATM (atomic force microscope). The basic concept is that piezoelectric actuators move a miniature cantilever arm (with a nm-sized tip) across the sample while a non-contact optical system measures the deflection of the cantilever caused by atomic scale features. The deflection is proportional to the normal force exerted by the sample on the probe tip and images are generated by raster scanning the sample [201]. One application of this technique was to measure the thickness and size distribution of sub-micron clay particles with diameters in the 0.1 to 1 pm size range and thickness from 0,01 to 0.12 pm [202]. 

These features of the Raman bands of the ZnO nanostructures can be extremely powerful for the in situ identification of orientation of ZnO nanostructures employed in a converse piezoelectric actuator directly in an assembled state [45]. While their study focused on ZnO nanostructures, the authors noted that the general features (Raman bands and the waveguiding effect) described are equally applicable to other wurtzite type nanostructures and the approach suggested might serve as a universal tool for the versatile characterization of GaN, ZnS, and CdSe from the wurtzite family, which are utilized for optoelectronics, lasing, and piezoelectricity. 

With the hard testing machines (Bhushan etal, 1988 Tusakamoto etal, 1987 Wu et ah, 1988), the indentation depth is controlled, for example, by means of a piezoelectric actuator. Force transducers used in existing designs include a load cell with a range from a few tens of micronewtons to 2 N (Wu etal., 1988 Wu 1991) a digital electrobalance with a resolution of 0.1 o.N, and a maximum of 0.3 N and a linear spring whose extension is measured by polarization interferometry. 

Actuators used for the active microvalve systems include solenoid plungers,bimetaUic actuators, and piezoelectric actuators. However, numerous other principles have been employed, such as springs, pneumatic pressure,or electrostatic or electromagnetic forces.Other microvalve systems have been developed that employ a variety of prin-... 

An additional advantage of the integrated circuit technology is the ability to integrate the various components, such as the transducer, reactor, valve, pump etc., within the electronic system, forming refined flow-analysis systems on silicon wafers. Several approaches, such as electrostatic, electromagnetic, piezoelectric, thermopneumatic and thermoelectric can be employed for force transduction in the microvalves, these are also applicable to micropumps. Based on these approaches, two versions of micropumps have been developed. These are connected in parallel the first pump (dual pump) is activated with periodic two-phase voltage, while the second pump (the buffer pump) is driven by two piezoelectric actuators. Microsensors of two kinds are described below a thermopile based- and a thermistor based microbiosensor. 

Lead zirconium titanate (PZT) is the most common material used for piezoelectric actuators. 

Cohen et al. [102,103] used a simple design with a movable microscope cover slide as lower plate and fixed top plate. The maximum plate separation was 100 pm and they were parallel to within 1pm. The lower plate was driven by a piezoelectric actuator with displacements up to 90 pm at frequencies <100 Hz. The sample between the plates was in contact with a reservoir of un-sheared bulk suspension. 

The thermal bending deformation can be cancelled by controlling the piezoelectric actuator pasted on the low temperature side. The stress discontinuity induced by the discontinuity of material parameters on the interface can be reduced by adding a graded piezoelectric layer between the main material and piezoelectric actuator. 

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