Acoustic devices

The main parts of the acoustic filter assembly are (i) ultrasonic transducer provided with compressed air cooling facility, (ii) flow channel, (iii) settling 

FIGURE 7B.11 Principle of acoustic separation and stages of cell aggregation leading to particle settling. (Reproduced from Hill and Harris (2007) with kind permission from Springer Science + Business Media LLC, New York, USA. 2007.) 

FIGURE 7B.12 Schematic of bioreactor using an acoustic separation device. (Reproduced from USER MANUAL BioSep ADH015 September 2001 with permission from Applikon Biotechnology B.V. 2001.) 

STIRRED TANK REACTORS FOR CELL CULTURE TECHNOLOGY 

The procedure described in the aforementioned publication can be summarized as follows  

A high molecular weight PP resin composition, has been prepared which has excellent acoustic properties and rigidity and high specific gravity suitable for use in acoustic instruments including speaker panels or boxes. 

The PP is either a homopolymer or a crystalline copolymer of PP with ethene, 1-butene, 1-pentene, 1-hexene, 4-methyl-l-pentene, 1-heptene, 1-octene or 1-decene as comonomers (28). 

Supplementary components include 10-60% of calcium carbonate with an average particle size of 1-20 p and barium sulfate. 

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The acoustical device component is placed in water and is configured like a conventional impulse echo equipment. The ultrasound wave passed the delay path and enters the specimen container through a very thin plastic window. The backside of the container is a steel plate and will also be used as a reference reflector to measure pn. 

The propagation of pressure waves such as acoustic wave, shock wave, and Prandtl-Meyer expansion through a gas-solid suspension is a phenomenon associated primarily with the transfer of momentum although certain processes of energy transfer such as kinetic energy dissipation and heat transfer between gas and solids almost always occur. Typical applications of the pressure wave propagation include the measurements of the solids concentration and flow rate by use of acoustic devices as well as detonation combustion such as in a rocket propellant combustor or in the barrel of a gun. 

One- and two-dimensional nanodomain configurations have been engineered in LiNbOs, RbTi0P04 and RbTi0As04 bulk fe crystals by the developed hvafm and indirect electron beam methods for a new generation of photonic and acoustic devices. 

Amico A, Natale C, Verona E (1997) Acoustic devices. In Kress Rogers (ed) Handbook of Biosensors and Electronic Noses, Medicine, Food, and the Environment. CRC, Boca Raton, p 197... 

Because acoustic wave devices are sensitive and respond rapidly, they are ideally suited for real-time monitoring of chemical and physical systems. As discussed in the introduction to this chapter, thin films represent a growing industrial and technological concern for a variety of applications. The use of acoustic devices to characterize the physical properties of these films has been dealt with in the previous sections. Here we describe how these devices can be used to monitor film formation or dissolution processes, or to observe and characterize film properties as a function of time (similar to the monitoring of diffusion in polymers described in Section 4.2.2). 

Perturbation mechanisms for the various acoustic devices were discussed in general terms in Chapter 3. In this chapter, these mechanisms are reviewed specifically in the context of chemical and biochemical analysis. Performance criteria are discussed, and the fundamental coating-analyte interactions giving rise to sensor responses are presented as a basis for classification. Relevant physical and chemical models of these interactions are described, and examples of analytical applications employing each type of interaction are given to illustrate their advantages and limitations. While references have been included to illustrate specific points, this chapter is not intended to comprise an exhaustive review of the literature, particularly for TSM resonators, for which the number of references is far too great to be fully reviewed here. For more detailed information on the diversity of sensor applications, the reader is referred to the many review articles that have been published on these topics [2-8,13-15]. 

In the context of resonant acoustic devices, Q =fiJBW, where fn is the resonant frequency and BW is the bandwidth it can equivalently be defuied as loU Pj, where o> is the angular frequency. Up is the peak total energy present in the device, and is the power dissipated by the device. For resonant systems, BW is the range of frequencies over which the reflected power is within 3 dB (a factor of two) of its minimum value, attained at fit, for non-resonant systems (e.g., delay lines), BW is the range of iiequencies over which the transmitted power is within a factor of two of its maximum value. 

Temperature variations can also produce drift due to stresses imposed on the acoustic device by packaging that has a different coefficient of expansion than the substrate material. If the acoustic device is rigidly mounted onto a material that expands at a different rate with temperature, then bending stress will be applied to the device, perturbing the AW velocity. This problem is discussed in more detail in Section 6.4.4. 

As the readers may see, quartz crystal resonator (QCR) sensors are out of the content of this chapter because their fundamentals are far from spectrometric aspects. These acoustic devices, especially applied in direct contact to an aqueous liquid, are commonly known as quartz crystal microbalance (QCM) [104] and used to convert a mass ora mass accumulation on the surface of the quartz crystal or, almost equivalent, the thickness or a thickness increase of a foreign layer on the crystal surface, into a frequency shift — a decrease in the ultrasonic frequency — then converted into an electrical signal. This unspecific response can be made selective, even specific, in the case of QCM immunosensors [105]. Despite non-gravimetric contributions have been attributed to the QCR response, such as the effect of single-film viscoelasticity [106], these contributions are also showed by a shift of the fixed US frequency applied to the resonator so, the spectrum of the system under study is never obtained and the methods developed with the help of these devices cannot be considered spectrometric. Recent studies on acoustic properties of living cells on the sub-second timescale have involved both a QCM and an impedance analyser thus susceptance and conductance spectra are obtained by the latter [107]. 

Zinc oxide (ZnO, wurtzite structure) eliminates oxygen on heating to form nonstoichio-metric colored phases, Zni+xO with x < 70 ppm. ZnO is almost transparent and is used as white pigment, polymer stabilizer, emollient in zinc ointments, creams and lotions, as well as in the production of Zu2Si04 for TV screens. A major application is in the rubber industry to lower the temperatures and to raise the rate of vulcanization. Furthermore, it is an n-type semiconductor (band gap 3.37 eV) and shows piezoelectric properties, making zinc oxide useful for microsensor devices and micromachined actuators. Other applications include gas sensors , solar cell windows and surface acoustic devices. ZnO has also been considered for spintronic application because of theoretical predictions of room-temperature ferromagnetism . 

The amplifying features of an electronic device can be combined with the attributes of an LB film to form sophisticated microsensors. However, optical and acoustic devices frequently show interesting threshold or resonance eflPects that can also form the basis of useful sensors. In this section, detailed results are presented only for acoustoelectric devices. 

Microelectromechanical systems (MEMS) combine the electronics of microchips with micromechanical features and microfluidics to create unique devices. The multitude of MEMS applications continues to grow including many types of accelerometers, radio frequency (RF) devices, variable capacitors, strain and pressure sensors, deformable micromirrors for image projection systems, vibrating micro-membranes for acoustic devices, ultrasound probes, micro-optical electromechanical systems (MOEMS) and MEMS gyroscopes, to name a few. 

Recently developed cell retention devices such as alternating tangential filtration (ATF) or an acoustic device (Biosep) can be fitted to existing bioreactors at contract organizations. 

Fleurat-Lessard, F. and Andrieu, A.J. 1986. Development of a rapid method to determine insect infestation in grain bins with electro-acoustic devices. In Proceedings of the 4th International Working Conference on Stored Product Protection (E. Donahaye and S. Navarro, eds), p. 643. Tel Aviv, Israel. 

Mankin, R.W., Shuman, D., and Coffelt, J.A. 1996. Noise shielding of acoustic devices for insect detection. J. Econ. Entomol. 89, 1301-1308. 

The performance of oscillators depends essentially on the stabihty of the acoustic device [7-9] no matter if working as electromechanical resonator or delay line. Because of its extraordinary importance we will concentrate further on resonators, namely quartz crystal resonators. However, the analysis is descriptive also for other piezoelectric materials and partly for delay line elements as well. 

A wide range of physical parameters are suitable for chemical sensing applications, consequently, there is a very wide variety of different transducers. Some examples of frequent transducing techniques are metal oxide semiconductor devices (MOS diodes and field effect transistors) relying e.g. on changes in electrical fields or opt(r)odes concerning optical phenomena such as absorbance and fluorescence, but also miniaturised capacities [1]. Mass-sensitive, or acoustic, devices constitute another very popular class of transducers. Within this chapter we will focus on this transducing technique and introduce its abihties and properties in combination with selective artificial interaction materials. 

The M M03 compounds crystallize with perovskite structures Figure 5.23), and exhibit ferroelectric and piezoelectric properties (see Section 13.9) which lead to uses in electrooptical and acoustic devices. 

AIN High powered integrated circuits acoustic devices... 

LiNbOj Piezoelectric electrooptic Optical memory displays acoustic devices wave guides lasers holography... 

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