Double piezoelectric defects in phononic crystals for ultrasonic transducers

Abstract

Significant prior research has explored elastic wave-energy localization via a defect mode of a phononic crystal (PnC). The integration of defect-introduced PnCs and piezoelectric materials has paved the path for the development of new conceptual products for applications in energy harvesters, wave filters, and ultrasonic sensors. Recently, an attempt has been made to deviate from this paradigm and design an ultrasonic transducer that generates elastic waves. Unfortunately, the previous works have been limited to a single-defect situation. Therefore, as an advanced approach, this work aims to expand the PnC design space into double defects, which will make the ultrasonic transducer useful at several frequencies. As a first step, this study targets longitudinal wave generation. To predict the wave-generation performance, a previous analytical model that was built for energy-harvesting purposes under a single-defect situation is modified to be suitable for the present wave-generation purpose under a double-defect situation. Moreover, two parametric studies are executed to analyze how the output responses change based on changes to the input voltage setting and the spacing between the double defects. We hope that these ultrasonic transducers can be potentially applicable for nondestructive testing in structural health monitoring and ultrasonic imaging in medical science.

Defect-Band Splitting of a One-Dimensional Phononic Crystal with Double Defects for Bending-Wave Excitation

“…This intriguing observation comes from the fact that the perspective of observing the defective PnC from the front (rear) for the configuration of (v PD1 (ω), v PD2 (ω)) = (0 V, 1 V) aligns precisely with its rear (front) view for the configura-tion of (v PD1 (ω), v PD2 (ω)) = (1 V, 0 V). Certainly, these aforementioned characteristics have already been corroborated in a prior reference [25], which comprehensively explores the excitation of longitudinal waves through a PnC featuring double piezoelectric defects.…”

“…It effectively safeguards against structural influences while simultaneously providing clear insight into the intricate interplay between applied input voltages on individual piezoelectric defects and the resulting velocity amplitude of excited bending waves as they propagate outward. Furthermore, the previous study that investigates the efficacy of the PnC with double piezoelectric defects demonstrates that this specific symmetry configuration exhibits the most favorable performance in exciting longitudinal waves [25,27]. Note that in this scenario of defect introduction, an even number of N always results in a non-symmetric configuration.…”

“…Prior research on piezoelectric effects has widely adopted such mathematical approaches to ensure the inclusion of piezoelectricity-related terms during spatial differential processes. Indeed, some analytical models, particularly those addressing longitudinal waves and transverse vibrations, have appealed remarkable agreement with finite-element-method results [25,26,47,48].…”

“…However, this area shows promising potential with only a handful of studies conducted so far. To demonstrate the significant impact of defective PnCs on the excitation of longitudinal waves, two analytical approaches rooted in the Rayleigh-Love theory have been presented [25,26]. These approaches account for single or double defects.…”

Simultaneous Determination of Young's Modulus and Density of Ultrathin Low‐k Films Using Surface Acoustic Waves

“…[5,6] Ultrasonic technology offers fast testing, ease of operation, nondestructiveness, and high sensitivity, making it a popular choice for NDT of material properties. [7][8][9][10] Surface acoustic wave (SAW) is an elastic wave that travels along the free surface of a solid media, with most energy concentrated near the surface and attenuating exponentially into the body. [11] The dispersion curve of SAW phase velocity propagating on a film/substrate structure contains valuable information about the physical parameters of the film and substrate.…”