Piezoelectric Diodes

This type of simple circuit (without the neon bulb or capacitor) is commonly used to operate doorbells, with a bell clapper attached to the armature, which hits a metal bell. It was also used for the older model telephone "ringers," before modern transistorized oscillators became available. Without the clapper and bell, it is still used a lot for various "buzzer" applications. (More modem buzzer designs use the piezoelectric diodes discussed in Chapters 14 and 15.)... 

Figure 2 shows the brief principle of a laser-detected FFM. A sample is put on a piezoelectrical tube (PZT), which scans X, Y plane and controls the feedback of Z axis. The laser beam from a diode is focused on the mirror of the free end of a cantilever with lens, and the reflected beam falls on the center of a position-sensitive detector (PSD), a four-quadrant photodiode. When the sample contacts with the tip and relatively moves under the control of a computer, the reflected beam deflects and changes the position on the PSD due to the twist and deflection of the cantilever caused by the changes of surface roughness, friction force, and adhesive force between the sample and the tip. The extension and re-... 

Functional fibres, filaments and yams are the basic building blocks of electrotextiles. The textile industry has demonstrated a remarkable capability to incorporate both natural and man-made filaments into yarns and fabrics to satisfy a wide range of physical parameters which survive the manufacturing process and are tailored to specific application environments. Electronic components can be fabricated within and/or on the surface of filaments and can subsequently be processed into functional yams and woven into fabrics. Passive components such as resistors, capacitors and inductors can be fabricated in several different manners. Diodes and transistors can be made on long, thin, flat strands of silicon or formed in a coaxial way. Progress has been made in the development of fibre batteries and fibre-based solar cells. In addition, a variety of actuated materials (piezoelectric, etc.) can be made into multiple long strands (filaments) and subsequently be woven into fabric. 

Figure 2 shows a schematic of a typical AFM instrument that consists of a cantilever-mounted tip, a Piezoelectric scanner, four position-sensitive photo detectors, a laser diode and a control unit. The process of operation of an AFM is relatively simple. The beam from the laser is directed against the back of the cantilever beam onto the quadrants of the photo detector. As the tip is moved across a sample, this causes the cantilever beam to bend or be twisted in manner that is proportional to the interaction force. This bending or twisting of the cantilever causes the position of the laser on the photo detector to be altered. The deflection of the cantilever beam can then be converted into a 3D topographical image of the sample surface (Gaboriaud and Dufrene, 2007 Kuznetsova et al., 2007 Lim et al., 2006). 

Fig. 2 Schematic representation of the basic detection elements of the scanning force microscope and of the piezoelectric transducers generating the displacement modulations for purposes of dynamic mechanical measurements. The dynamic components of the tip-sample forces resulting from the normal/lateral displacement modulations are detected via the torsion/bending of the microscopic cantilever and the deflection of the laser beam reflected off the rear side of the cantilever. The positional shift of the latter is registered by means of a segmented photo-diode...

To make sure that upon the pressure change to be recorded the intensity of the interference pattern on the diode stays within the linear range, the interference pattern can be shifted making use of the arbitrary phase in Eq. (4). In practice the phase shift is provided by changing the position of mirror 2 (Fig. 2) via a piezoelectric transducer. 

Visual and audio feedback information is provided to the user by light-emitting diodes (LED), liquid crystal displays (LCD), and piezoelectric transducers. This information can indicate that the system is working, show errors or warnings, signal system maintenance needs (such as battery replacement), or display the amount of drug that has been delivered. 

In this entry, we focus on the discussion of the platform technology for electrochemical sensors, metal oxide semiconductive (MOS) sensors, and piezoelectric based quartz crystal microbalance (QCM) sensors. There are other types of chemical sensors, such as optical sensors, Schottky diode based sensors, calorimetric sensors, field-effect transistor (FET) based sensors, surface acoustic wave sensors, etc. Information of these specific sensors can be found elsewhere and in current journals on sensor technologies. Because of the increasing importance of microfabricated sensors, a brief discussion of microsensors is also given. 

We investigated a thermoelectric thermal sensor which responded to heat in a short time and generated electricity to drive electric parts such as a light emitting diode or a piezoelectric buzzer. The sensor was composed of the insulated metal sheet and thermoelectric thick films on it. The device contained 8 pairs of iron disilicide thermocouple connected in series, generated 1.5 V within 5 seconds and 2.8 V within 25 seconds reacting to a gas flame. 

A crystal of galena was used in the cat s whisker radio (in the point-contact diode) Cu wire was slowly moved across the galena crystal to tune the device. Thin slices of tourmaline crystals were used in making the pressure gauges that measured the power dissipated by the first atom bomb explosions (tourmaline is piezoelectric). 

Light-emitting diodes Superconductors Piezoelectrics Ferroelectrics Solid electrolytes... 

As discussed in Section 10.2.3, PVP and DNA have been used to wrap and water-solublize SWNTs. For specific actuator, electrical and electro-optic applications, SWNTs have been wrapped by piezoelectric polyvinylidene fluoride and trifluor-oethylene copolymer [50] or with conjugated polymers [51, 52]. The conjugated polymer used to form a composite with MWNTs and an electron-transport layer in light-emitting diodes is poly(m-phenylene-vinylene-co-2,5-dioctyloxy-p-phenylene-vinylene) (PmPV) [53]. Wrapping coupled with electron doping has been achieved with polyethylene imine to form p-n junction devices ([40], see footnote 1). 

For a low-frequency, Mach-Zehnder modulator, the impedance is dominated by the electrode capacitance and resistance as shown in Fig. 9.57. A Smith chart plot for a MZM is shown in Fig. 9.58. Unlike the laser diode, a modulator on lithium niobate has no junctions consequently the impedance is independent of modulator bias. As was the case with the diode laser, it is often important to match the modulator impedance to the system impedance, typically 50 or 75 real. However, unlike the diode laser, modulators fabricated in electro-optic materials that are also piezoelectric can have perturbations in their impedance due to coupling of some of the modulation signal into compressional waves. The coupling can be significant at frequencies where the modulator crystal is resonant. The dashed curve in Fig. 9.58 shows an acoustic resonance at 150 MHz. A number of techniques (Betts, Ray and Johnson, 1990) have been developed to suppress these acoustic modes to insignificant levels, as is evidenced by the solid curve in Fig. 9.56. 

Electrical interconnections are made both by conductive adhesives and wire bonding The fluid handling is accomplished by means of piezoelectric micro fluidic injectors and micro fluidic diodes The function principle is explained in section 3 The main electronic functions are implemented on a programmable ASIC... 

One active area of research is completely missing. These are the optical and electrical properties, with effects such as the high conductivity of doped conjugated polymers, electro-luminescence in polymeric light emitting diodes, or the ferro- and piezoelectricity of poly(vinylidene fluoride), to cite only a few examples. There is no good reason for this omission, only that I did not want to overload the book with another topic of different character which, besides, mostly employs concepts which are known from the physics of semi-conductors and low molar mass molecules. 

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