Layer guided shear horizontally polarized acoustic plate modes

McHale, Glen; Newton, Michael I.; Martin, F.

doi:10.1063/1.1465103

Cited by 25 publications

(25 citation statements)

References 23 publications

(27 reference statements)

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“…The difference between the devices is that the Love wave displacement has an antinode at the top surface of the layer and decays with depth into the substrate whereas the SH-APM has antinodes at both the top surface of the layer and at the lower surface of the substrate. Thus, within a model neglecting electric field effects, it is possible to use a common set of equations of motion and boundary conditions to describe both the Love wave on a finite substrate and the SH-APM with a guiding layer [16,17]. In this approach, the substrate and layer solutions can be written in the forms, …”

Section: Layer-guided Sh-apmsmentioning

confidence: 99%

Generalized concept of shear horizontal acoustic plate mode and Love wave sensors

McHale

2003

Meas. Sci. Technol.

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An approach to mass and liquid sensitivity for both the phase velocity and insertion loss of shear mode acoustic wave sensors based on the dispersion equations for layered systems is outlined; the approach is sufficiently general to allow for viscoelastic guiding layers. An equation for the phase velocity and insertion loss sensitivities is given which depends on the slope of the complex phase velocity dispersion curves. This equation contains the equivalent of the Sauerbrey and Kanazawa equations for loading of a quartz crystal microbalance by rigid mass and Newtonian liquids, respectively, and also describes surface loading by viscoelastic layers. The theoretical approach can be applied to a four-layer system, with any of the four layers being viscoelastic, so that mass deposition from a liquid can also be modelled. The theoretical dispersion equation based approach to layer-guided shear horizontal acoustic wave modes on finite substrates presented in this work, provides a unified view of Love wave and shear horizontal acoustic plate mode (SH-APM) devices, which have been generally regarded as distinct in sensor research. It is argued that SH-APMs with guiding layers possessing shear acoustic speeds lower than that of the substrate and Love waves are two branches of solution of the same dispersion equation. The layer guided SH-APMs have a phase velocity higher than that of the substrate and the Love waves a phase velocity lower than that of the substrate. Higher order Love wave modes are continuations of the layer guided SH-APMs. The generalized concept of SH-APMs and Love waves provides a basis for understanding the change in sensitivity with higher frequency operation and the relationship between multiple modes in Love wave sensors. It also explains why a relatively thick layer of a high loss polymer can be used as a waveguide layer and so extends the range of materials that can be considered experimentally. Moreover, it is predicted that a new type of sensor, a layer-guided SH-APM sensor, can be constructed in a manner analogous to a Love wave device. The sensitivity of such a device is predicted to approach that of a Love wave sensor whilst retaining the advantage of the SH-APM of using the face opposite the one possessing the transducers as the sensing surface.

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Section: Layer-guided Sh-apmsmentioning

confidence: 99%

Generalized concept of shear horizontal acoustic plate mode and Love wave sensors

McHale

2003

Meas. Sci. Technol.

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“…In our previous treatment of Love waves with elastic mass guiding layers we plotted displacement profiles for a range of guiding layer thicknesses. 20 In any mode the upper, free, surface of the guiding layer is an antinode and the displacement decays into the substrate. For the first Love wave mode (nϭ0) and very thin guiding layers, the displacement in the substrate decays gently so that the substrate displacement approximates a plane wave and this plane wave pattern extends into the guiding layer.…”

Section: B Numerical Results For Phase Speed and Insertion Lossmentioning

confidence: 99%

“…͑42͒ in Ref. 20. It should be noted that since T s 0 wϭ jm the substrate thickness w is proportional to 1/ , i.e.,…”

Section: Sh-apm "Mì0… Perturbationmentioning

confidence: 96%

“…͑33͒ in Ref. 20. The limit →ϱ and ␦ 2 2 /2v s 2 ϭ␦ 2 k s 2 /2→0 is equivalent to taking the limit v s ӷv f in Eq.…”

Section: Sh-saw Perturbationmentioning

confidence: 99%

“…[19][20][21] This involved extending the theoretical treatment of both Love wave sensors with guiding layers composed of elastic mass to Love waves on finite thickness substrates and of SH-APMs to SH-APMs coated by waveguiding layers. In this previous treatment, higher order Love wave modes were shown to be continuations of the layer-guided SH-APMs and it was shown that significantly enhanced mass sensitivity could be obtained for SHAPMs by the use of a waveguiding layer.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical mass, liquid, and polymer sensitivity of acoustic wave sensors with viscoelastic guiding layers

McHale

Newton

Martin

2003

Journal of Applied Physics

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The theoretical sensitivity of Love wave and layer-guided shear horizontal acoustic plate mode ͑SH-APM͒ sensors for viscoelastic guiding layers and general loading by viscoelastic materials is developed. A dispersion equation previously derived for a system of three rigidly coupled elastic mass layers is modified so that the second and third layers can be viscoelastic. The inclusion of viscoelasticity into the second, wave guiding layer, introduces a damping term, in addition to a phase velocity shift, into the response of the acoustic wave system. Both the waveguiding layer and the third, perturbing layer, are modeled using a Maxwell model of viscoelasticity. The model therefore includes the limits of loading of both nonguided shear horizontal surface acoustic wave and acoustic plate mode ͑APM͒ sensors, in addition to Love wave and layer-guided SH-APM sensors, by rigidly coupled elastic mass and by Newtonian liquids. The three-layer model is extended to include a viscoelastic fourth layer of arbitrary thickness and so enable mass deposition onto an immersed Love wave or layer-guided SH-APM sensor to be described. A relationship between the change in the complex velocity and the slope of the complex dispersion curve is derived and the similarity to the mass and liquid sensor response of quartz crystal microbalances is discussed. Numerical calculations are presented for the case of a Love wave device in vacuum with a viscoelastic waveguiding layer. It is shown that, while a particular polymer relaxation time may be chosen such that the effect of viscoelasticity on the real part of the phase speed is relatively small, it may nonetheless induce a large insertion loss. The potential or the use of insertion loss as a sensor parameter is discussed.

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Digital twin of surface acoustic wave transceivers for a computational design of an optimal wave guiding layer thickness

Baler,

Okyar,

Abali

2024

Comput Mech

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Detection of biomarkers is exploited in lab-on-a-chip devices by means of Love type Surface Acoustic Waves (SAW). Finger type arrangement of electrodes, used for InterDigital-Transducers (IDT), perform well to create and detect SAW by using electro-mechanical coupling. Efficiency of such a transceiver depends on design parameters such as chosen material orientation, thickness, placement of electrodes. An optimized design reduces production costs, hence, we need a digital twin of the device with multiphysics simulations that compute deformation and electric field. In this study, we develop a framework with the open-source package called FEniCS for modal and transient analyses of IDTs by using the Finite Element Method (FEM). Specifically, we discuss all possible sensor design parameters and propose a computational design guideline that determines the “best” thickness parameter by maximizing mass sensitivity, thus, efficiency for a Love surface acoustic wave sensor.

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Layer guided shear horizontally polarized acoustic plate modes

Cited by 25 publications

References 23 publications

Generalized concept of shear horizontal acoustic plate mode and Love wave sensors

Generalized concept of shear horizontal acoustic plate mode and Love wave sensors

Theoretical mass, liquid, and polymer sensitivity of acoustic wave sensors with viscoelastic guiding layers

Digital twin of surface acoustic wave transceivers for a computational design of an optimal wave guiding layer thickness

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