Capacitive micromachined ultrasonic Lamb wave transducers using rectangular membranes

Rayleigh–bloch waves in CMUT arrays

“…5 Each element contains 80 × 5 rectangularly placed cells with a separation of s = 3 μm. Elements are driven at 0.70 mHz by linearly increasing delays of 0, 1/8, 2/8, …, 47/8 μs (Δ = 1/8 μs) to simulate a case where the beam is steered at an angle of θ = 30° with respect to the normal.…”

“…The artifacts observed in the point spread function of cmUT arrays were attributed to crosstalk between the elements [3]. The spurious responses were believed to be due either to stoneley waves [4] in the interface or to lamb waves [5] in the substrate. scholte [6] waves traveling in the interface between the array surface and the immersion medium were also held responsible.…”

Theory of Lamb Wave Transducers and Their Applications for Gas and Liquid Sensing

“…Electrostatic transduction has been presented also [6,[9][10][11][12]. It uses a silicon plate and two diaphragm grating structure transducers (DGT) located respectively at the two ends of the plate for generating and receiving Lamb waves respectively, shown in Fig.…”

Nonlinear sensitivity of capacitive micromachined ultrasonic Lamb wave transducers

“…Thus, the phase velocities of the A0 wave at low fd values can be also determined by (7). The phase velocities calculated in the range of 100 ≤ fd by using these two ways, i.e., determined by using the 3D-plot of Figure 1 and the approximate formula, respectively, are listed in Table I for easy reference.…”

“…Also, note that the first-order bending mode of long rectangular diaphragms has been used to excite and receive the Lamb waves in a silicon plate for measuring the change of the humidity in the environment, and such a capacitive LWT shows some merits better than piezoelectric ones. 6,7 Therefore, the micromachined CLWTs based-on the second-order bending mode excitation mechanism are particularly attractive as gravimetric sensors for chemical and biological measurements. This paper performs further an in-deep study in the theoretical basis of such CLWTs, and focuses on another important issue, i.e.…”