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This paper aims to Separation and sorting of biological cells is desirable in many applications for analyzing cell properties, such as disease diagnostics, drugs delivery, chemical processing and therapeutics.

Acoustic energy-based bioparticle separation is a simple, viable, bio-compatible and contact-less technique using, which can separate the bioparticles based on their density and size, with-out labeling the sample particles.

Conventionally available bioparticle separation techniques as fluorescence and immunomagnetic may cause a serious threat to the life of the cells due to various compatibility issues. Moreover, they also require an extra pre-processing labeling step. Contrarily, label-free separation can be considered as an alternative solution to the traditional bio-particle separation methods, due to their simpler operating principles and lower cost constraints. Acoustic based particle separation methods have captured a lot of attention among the other reported label-free particle separation techniques because of the numerous advantages it offers.

This study tries to briefly cover the developments of different acoustic-based particle separation techniques over the years. Unlike the conventional surveys on general bioparticles separation, this study is focused particularly on the acoustic-based particle separation. The study would provide a comprehensive guide for the future researchers especially working in the field of the acoustics, in studying and designing the acoustic-based particle separation techniques.

The study insights a brief theory of different types of acoustic waves and their interaction with the bioparticles is considered, followed by acoustic-based particle separation devices reported till the date. The integration of acoustic-based separation techniques with other methods and with each other is also discussed. Finally, all major aspects like the approach, and productivity, etc., of the adopted acoustic particle separation methods are sketched in this article.

This study aims to understand the influence of megasonic (MS)-assisted agitation on printed circuit boards (PCBs) electroplated using copper (Cu) electrolyte solutions to improve plating efficiencies through enhanced ion transportation.

The impact of MS-assisted agitation on topographical properties of the electroplated surfaces was studied through a design of experiments by measuring surface roughness, which is characterised by values of the parameter Ra as measured by white light phase shifting interferometry and high-resolution scanning electron microscopy.

An increase in Ra from 400 to 760 nm after plating was recorded for an increase in acoustic power from 45 to 450 W. Roughening increased because of micro-bubble cavitation energy and was supported through direct imaging of the cavitation. Current thieving effect by the MS transducer induced low currents, leading to large Cu grain frosting and reduction in the board quality. Current thieving was negated in plating trials through specific placement of transducer. Wavy electroplated surfaces, due to surface acoustic waves, were also observed to reduce the uniformity of the deposit.

The formation of unstable transient cavitation and variation of the topology of the Cu surface are unwanted phenomena. Further plating studies using MS agitation are needed, along with fundamental simulations, to determine how the effects can be reduced or prevented.

This study can help identify manufacturing settings required for high-quality MS-assisted plating and promote areas for further investigation, leading to the development of an MS plating manufacturing technique.

This study quantifies the topographical changes to a PCB surface in response to MS agitation and evidence for deposited Cu artefacts due to acoustic effects.

This paper aims to determine the important role of acoustic wave devices in sensing applications such as automotive applications, industrial applications and commercial applications.

The paper provides a comprehensive overview of acoustic wave technology and highlights an example of one commercial implementation of its technology for sensing application: a commercially available real‐time, online threaded bolt viscosity sensor.

The commercially available viscosity sensor can be readily applied in field operations or installed directly on the equipment for continuous monitoring of viscosity to enable technicians/mechanics to test the oil in minutes.

The paper introduces a new product for the sensing industry.

Surface acoustic wave (SAW) sensors have attracted great attention worldwide for a variety of applications in measuring physical, chemical and biological parameters. However, stability has been one of the key issues which have limited their effective commercial applications. To fully understand this challenge of operation stability, this paper aims to systematically review mechanisms, stability issues and future challenges of SAW sensors for various applications.

This review paper starts with different types of SAWs, advantages and disadvantages of different types of SAW sensors and then the stability issues of SAW sensors. Subsequently, recent efforts made by researchers for improving working stability of SAW sensors are reviewed. Finally, it discusses the existing challenges and future prospects of SAW sensors in the rapidly growing Internet of Things-enabled application market.

A large number of scientific articles related to SAW technologies were found, and a number of opportunities for future researchers were identified. Over the past 20 years, SAW-related research has gained a growing interest of researchers. SAW sensors have attracted more and more researchers worldwide over the years, but the research topics of SAW sensor stability only own an extremely poor percentage in the total researc topics of SAWs or SAW sensors.

Although SAW sensors have been attracting researchers worldwide for decades, researchers mainly focused on the new materials and design strategies for SAW sensors to achieve good sensitivity and selectivity, and little work can be found on the stability issues of SAW sensors, which are so important for SAW sensor industries and one of the key factors to be mature products. Therefore, this paper systematically reviewed the SAW sensors from their fundamental mechanisms to stability issues and indicated their future challenges for various applications.

This paper aims to investigate the response behavior of the surface acoustic wave (SAW) sensor under the loading of micro-particles and to evaluate the feasibility of using the SAW sensor to study the micro-contact of the particle–plane interface.

An analytical perturbation theory of the coupled system of particle and SAW is presented. It shows that in the weak-coupling regime, the SAW sensor detects the coupling stiffness rather than the additional mass of the particle at the interface. The frequency perturbation formula expressed in parameters of the geometry and mechanical properties of the contact is further derived. The frequency shift of a 262-MHz Rayleigh-type SAW in the oscillation configuration under the loading of multiple starch particles of different sizes has been measured.

The experiment results of a linear relationship between the frequency increase and the sum of the radius of particles to the power of 2/3 verified the validity of the theory of linking the SAW response to the geometry and mechanical properties of the contact.

The SAW sensor could serve as a new candidate for studying the details of mechanical properties of the micro-contact of the interface.

This paper aims to give an overview about the state of wireless passive surface acoustic wave (SAW) gas sensor used in the detection of chemical vapor. It also discusses a variety of different architectures including delay line and array sensor for gas detection, and it is considered that this technology has a good application prospect.

The authors state the most of the wireless passive SAW methods used in gas sensing, such as CO2, CO, CH4, C2H4, NH3, NO2, et al., the sensor principles, design procedures and technological issues are discussed in detail; their advantages and disadvantages are also summarized. In conclusion, it gives a prospect of wireless passive SAW sensor applications and proposes the future research field might lie in the studying of many kinds of harmful gases.

In this paper, the authors will try to cover most of the important methods used in gas sensing and their recent developments. Although wireless passive SAW sensors have been used successfully in harsh environments for the monitoring of temperature or pressure, the using in chemical gases are seldom reported. This review paper gives a survey of the present state of wireless passive SAW sensor in gas detection and suggests new and exciting perspectives of wireless passive SAW gas sensor technology.

The authors will review most of the methods used in wireless passive SAW sensor and discuss the current research status and development trend; the potential application in future is also forecasted.

The authors will review most of the methods used in wireless passive SAW sensor and discuss the current research status and development trend; the potential application in future is also forecasted.

The purpose of this paper is to model multilayer structure surface acoustic wave (SAW) sensors, incorporated in CMOS or micro‐electro‐mechanical system integrated circuits, and to derive the corresponding wave velocity as an analytic expression in terms of the layers‘ thickness and density, which is suitable for analysis and design.

The method is based on an electro‐mechanical equivalent model of multilayer structure SAW sensors. A multilayered SAW device is represented by a two‐port electrical equivalent circuit consisting of three parts: input transducer, output transducer, and between them the delay line, which is the sensing part. The sensing part is modelled as a mechanical two‐port network. The wave velocity is calculated using analogy between the mechanical and electrical quantities and the fact that the wave motion of the SAW extends below the surface to a depth of about one wavelength.

The presented model predicts very efficiently and accurately the velocity of SAW sensors with multilayer substrates in the case where the thicknesses of upper layers are much smaller than the signal wavelength. The velocity can be calculated from the formula, so that elaborate numerical computations involving partial differential equations are avoided.

The model and the velocity calculation can be applied only to acoustically thin upper and middle layers where acoustically thin means that a layer is sufficiently thin and rigid (large shear modulus). The presented results provide a starting‐point for further research in the analysis and design of sensors fabricated using AlGaN, GaN, AlN/diamond.

Since the majority of SAW sensors is designed with acoustically thin layers, the proposed model and calculation can be of interest for many practical material combinations. The presented model and calculation can be used in most cases of the optimal sensor design with respect to the sensor sensitivity or required area on the sensor chip.

The paper presents a new original model of multilayer structure SAW sensors and a new method of SAW velocity calculation. The method gives good results, with much simpler calculations than in the wave equation method, in cases where certain layers are acoustically thin.

The purpose of this paper is to investigate the problem of the existence and propagation of a surface SH wave at the interface of two magneto‐electro‐elastic half‐spaces.

Equations of motions for magneto‐electro‐elastic materials have been used with coupling between mechanical, electric and magnetic fields. The problem is solved for four different sets of boundary conditions.

The results show that, for appropriate choice of material parameters, a non dispersive surface wave can propagate at the interface of these media. The existence condition is easier to satisfy for an electrically closed contact or no electromagnetic contact between two half‐spaces. The existence conditions can be easily satisfied for all four sets of boundary conditions if the two half‐spaces have their main symmetry axis, both parallel to the interface and perpendicular to the propagation direction, directed in the opposite directions. In this case the SH surface wave can always propagate if the two media are identical.

The magneto‐electric coupling effect has extensive applications, for example in electronic packaging, acoustic devices and medical ultrasonic imaging. The results of this paper give better understanding of the effects of the boundary conditions on the propagation of SH surface waves in magneto‐electro‐elastic materials.

The purpose of study to this article is to analyze the Rayleigh wave propagation in an isotropic dry sandy thermoelastic half-space. Various wave characteristics, i.e wave velocity, penetration depth and temperature have been derived and represented graphically. The generalized secular equation and classical dispersion equation of Rayleigh wave is obtained in a compact form.

The present article deals with the propagation of Rayleigh surface wave in a homogeneous, dry sandy thermoelastic half-space. The dispersion equation for the proposed model is derived in closed form and computed analytically. The velocity of Rayleigh surface wave is discussed through graphs. Phase velocity and penetration depth of generated quasi P, quasi SH wave, and thermal mode wave is computed mathematically and analyzed graphically. To illustrate the analytical developments, some particular cases are deliberated, which agrees with the classical equation of Rayleigh waves.

The dispersion equation of Rayleigh waves in the presence of thermal conductivity for a dry sandy thermoelastic medium has been derived. The dry sandiness parameter plays an effective role in thermoelastic media, especially with respect to the reference temperature for η = 0.6,0.8,1. The significant difference in η changes a lot in thermal parameters that are obvious from graphs. The penetration depth and phase velocity for generated quasi-wave is deduced due to the propagation of Rayleigh wave. The generalized secular equation and classical dispersion equation of Rayleigh wave is obtained in a compact form.

Rayleigh surface wave propagation in dry sandy thermoelastic medium has not been attempted so far. In the present investigation, the propagation of Rayleigh waves in dry sandy thermoelastic half-space has been considered. This study will find its applications in the design of surface acoustic wave devices, earthquake engineering structural mechanics and damages in the characterization of materials.

The purpose of this paper is to theoretically analyze the propagation of Love-type wave in an irregular piezoelectric layer superimposed on an isotropic elastic substrate.

The perturbation technique and Fourier transform have been applied for the solution procedure of the problem. The closed-form expressions of the dispersion relation have been analytically established considering different type of irregularities, namely, rectangular and parabolic for both the cases of electrically open and short conditions.

The study reveals that the phase velocity of Love-type wave is prominently influenced by wave number, size of irregularity, piezoelectric constant and dielectric constant of an irregular piezoelectric layer. Numerical simulation and graphical illustrations have been effectuated to depict the pronounced impact of aforementioned affecting parameters on the phase velocity of Love-type wave. The major highlight of the paper is the comparative study carried out for rectangular irregularity and parabolic irregularity in both electrically open and short conditions. Classical Love wave equation has been recovered for both the electrical conditions as the limiting case when both media are elastic and interface between them is regular.

The consequences of the study can be utilized in the design of surface acoustic wave devices to enhance their efficiency, as the material properties and the type of irregularities present in the piezoelectric layer enable Love-type wave to propagate along the surface of the layer promoting the confinement of wave for a longer duration.

Up to now, none of the authors have yet studied the propagation of Love waves in a piezoelectric layer overlying an isotropic substrate involving both parabolic and rectangular irregularities. Further, the comparative study of rectangular irregularity and parabolic irregularity for both the cases of electrically open and short conditions elucidating the latent characteristics is among the major highlights and reflects the novelty of the present study.