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Longitudinal modes along thin piezoelectric waveguides for liquid sensing applications.

Caliendo C - Sensors (Basel) (2015)

Bottom Line: Enhanced performances, such as a K2 as high as 8.5% and a phase velocity as high as 16,700 m/s, were demostrated for the ZnO- and BN-based waveguides, as an example.The relative velocity changes, and the inertial and viscous sensitivities of the first symmetric and anti-symmetric mode, S0 and A0, propagating along thin plates bordered by a viscous liquid were derived using the perturbation approach.The present study highlights the feasibility of the piezoelectric waveguides to the development of high-frequency, integrated-circuits compatible electroacoustic devices suitable for working in liquid environment.

View Article: PubMed Central - PubMed

Affiliation: Istituto di Acustica e Sensori O. M. Corbino, IDASC-CNR, Via del Fosso del Cavaliere 100, 00133 Roma, Italy. cinzia.caliendo@idasc.cnr.it.

ABSTRACT
The propagation of longitudinally polarized acoustic modes along thin piezoelectric plates (BN, ZnO, InN, AlN and GaN) is theoretically studied, aiming at the design of high frequency electroacoustic devices suitable for work in liquid environments. The investigation of the acoustic field profile across the plate revealed the presence of longitudinally polarized Lamb modes, travelling at velocities close to that of the longitudinal bulk acoustic wave propagating in the same direction. Such waves are suitable for the implementation of high-frequency, low-loss electroacoustic devices operating in liquid environments. The time-averaged power flow density, the phase velocity and the electroacoustic coupling coefficient K2 dispersion curves were studied, for the first (S0) and four higher order (S1, S2, S3, S4) symmetrical modes for different electrical boundary conditions. Two electroacoustic coupling configurations were investigated, based on interdigitated transducers, with or without a metal floating electrode at the opposite plate surface. Enhanced performances, such as a K2 as high as 8.5% and a phase velocity as high as 16,700 m/s, were demostrated for the ZnO- and BN-based waveguides, as an example. The relative velocity changes, and the inertial and viscous sensitivities of the first symmetric and anti-symmetric mode, S0 and A0, propagating along thin plates bordered by a viscous liquid were derived using the perturbation approach. The present study highlights the feasibility of the piezoelectric waveguides to the development of high-frequency, integrated-circuits compatible electroacoustic devices suitable for working in liquid environment.

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Cross sectional normalized distribution of normal (U3) and longitudinal (U1) displacements for: (a) AM propagating along the BN plate with hBN/λ = 0.3; (b) S1 mode for hBN/λ = 1; (c) S2 mode for hBN/λ = 1.97; (d) S3 mode for hBN/λ = 2.95.
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sensors-15-12841-f002: Cross sectional normalized distribution of normal (U3) and longitudinal (U1) displacements for: (a) AM propagating along the BN plate with hBN/λ = 0.3; (b) S1 mode for hBN/λ = 1; (c) S2 mode for hBN/λ = 1.97; (d) S3 mode for hBN/λ = 2.95.

Mentions: The fundamental symmetric Lamb mode, S0, as well as the higher order modes, are elliptically polarized and have higher velocity than the surrounding liquid medium: thus they are not suitable for sensing applications in liquids except in some special cases. These cases include: (1) the linearly polarized AMs that are a branch of the S0 mode; (2) the higher order symmetric modes just for specific plate normalized thicknesses. The former propagate at a velocity a little lower than the vLBAW, while the latter at the velocity of the LBAW. Unlike the AMs, for these modes the displacement component U3 vanishes on the plate surfaces, while it shows non- values into the bulk of the plate, as shown in Figure 2 where the field profile of the fundamental and of the three higher order symmetric modes (S1, S2 and S3) propagating along a BN plate are depicted. Here the BN field profile has been taken as example of the behavior of all the other piezoelectric materials. Figure 2a shows the acoustic field profile of the AM propagating along a BN plate 0.3λ thick. Figure 2b–d show the acoustic field profile of the S1, S2 and S3 modes propagating along the BN plate with normalized thickness hBN/λ =1, 1.97, and 2.95, respectively. The displacement amplitudes are normalized by the U1 value at the free surface of the plate.


Longitudinal modes along thin piezoelectric waveguides for liquid sensing applications.

Caliendo C - Sensors (Basel) (2015)

Cross sectional normalized distribution of normal (U3) and longitudinal (U1) displacements for: (a) AM propagating along the BN plate with hBN/λ = 0.3; (b) S1 mode for hBN/λ = 1; (c) S2 mode for hBN/λ = 1.97; (d) S3 mode for hBN/λ = 2.95.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507606&req=5

sensors-15-12841-f002: Cross sectional normalized distribution of normal (U3) and longitudinal (U1) displacements for: (a) AM propagating along the BN plate with hBN/λ = 0.3; (b) S1 mode for hBN/λ = 1; (c) S2 mode for hBN/λ = 1.97; (d) S3 mode for hBN/λ = 2.95.
Mentions: The fundamental symmetric Lamb mode, S0, as well as the higher order modes, are elliptically polarized and have higher velocity than the surrounding liquid medium: thus they are not suitable for sensing applications in liquids except in some special cases. These cases include: (1) the linearly polarized AMs that are a branch of the S0 mode; (2) the higher order symmetric modes just for specific plate normalized thicknesses. The former propagate at a velocity a little lower than the vLBAW, while the latter at the velocity of the LBAW. Unlike the AMs, for these modes the displacement component U3 vanishes on the plate surfaces, while it shows non- values into the bulk of the plate, as shown in Figure 2 where the field profile of the fundamental and of the three higher order symmetric modes (S1, S2 and S3) propagating along a BN plate are depicted. Here the BN field profile has been taken as example of the behavior of all the other piezoelectric materials. Figure 2a shows the acoustic field profile of the AM propagating along a BN plate 0.3λ thick. Figure 2b–d show the acoustic field profile of the S1, S2 and S3 modes propagating along the BN plate with normalized thickness hBN/λ =1, 1.97, and 2.95, respectively. The displacement amplitudes are normalized by the U1 value at the free surface of the plate.

Bottom Line: Enhanced performances, such as a K2 as high as 8.5% and a phase velocity as high as 16,700 m/s, were demostrated for the ZnO- and BN-based waveguides, as an example.The relative velocity changes, and the inertial and viscous sensitivities of the first symmetric and anti-symmetric mode, S0 and A0, propagating along thin plates bordered by a viscous liquid were derived using the perturbation approach.The present study highlights the feasibility of the piezoelectric waveguides to the development of high-frequency, integrated-circuits compatible electroacoustic devices suitable for working in liquid environment.

View Article: PubMed Central - PubMed

Affiliation: Istituto di Acustica e Sensori O. M. Corbino, IDASC-CNR, Via del Fosso del Cavaliere 100, 00133 Roma, Italy. cinzia.caliendo@idasc.cnr.it.

ABSTRACT
The propagation of longitudinally polarized acoustic modes along thin piezoelectric plates (BN, ZnO, InN, AlN and GaN) is theoretically studied, aiming at the design of high frequency electroacoustic devices suitable for work in liquid environments. The investigation of the acoustic field profile across the plate revealed the presence of longitudinally polarized Lamb modes, travelling at velocities close to that of the longitudinal bulk acoustic wave propagating in the same direction. Such waves are suitable for the implementation of high-frequency, low-loss electroacoustic devices operating in liquid environments. The time-averaged power flow density, the phase velocity and the electroacoustic coupling coefficient K2 dispersion curves were studied, for the first (S0) and four higher order (S1, S2, S3, S4) symmetrical modes for different electrical boundary conditions. Two electroacoustic coupling configurations were investigated, based on interdigitated transducers, with or without a metal floating electrode at the opposite plate surface. Enhanced performances, such as a K2 as high as 8.5% and a phase velocity as high as 16,700 m/s, were demostrated for the ZnO- and BN-based waveguides, as an example. The relative velocity changes, and the inertial and viscous sensitivities of the first symmetric and anti-symmetric mode, S0 and A0, propagating along thin plates bordered by a viscous liquid were derived using the perturbation approach. The present study highlights the feasibility of the piezoelectric waveguides to the development of high-frequency, integrated-circuits compatible electroacoustic devices suitable for working in liquid environment.

Show MeSH
Related in: MedlinePlus