Due to the limited availability and high depletion rates of nonrenewable energy sources as well as environmental concerns, the scientific community is urged to explore and harness alternative, clean energy sources. In this paper, a novel piezoelectric energy harvester based on a metamaterial structure is proposed, which is capable of scavenging energy from low-frequency, multi-axial ambient vibrations. The proposed energy harvester is based on a mass-in-mass phononic crystal structure and is comprised of a spherical heavy core resonator and piezoelectric wafers, encapsulated in a cylindrical rubber matrix, and encased in a rigid cubic frame. The proposed cell behaves effectively such as a negative mass in the vicinity of its resonance frequencies and entraps the vibration energy as dynamic strain. The captured kinetic energy is then transformed to electric potential using three lead–zentrale–Teichmann wafers, optimally embedded in the cell’s soft constituent. In this paper, the proposed energy harvester cell is analytically modeled, numerically simulated via COMSOL Multiphysics software, and experimentally validated using a variety of uni- and multi-axial vibration excitations.

In this study, inspired from human cochlea, we propose an artificial basilar membrane structure based on an array of gold electrodes microfabricated along the opposite surfaces of a piezoelectric continuum. The proposed piezoelectric continuum features an isosceles trapezoidal geometry and is situated atop an elastomer matrix with embedded electrode grooves and a duct. At first, a detailed analytical model is presented, which formulates the continuum’s planar deflection equation, governing its elastodynamic behavior. Subsequently, in order to verify the analytical outcomes, a multiphysics finite-element analysis is performed in COMSOL®. Both analytical and numerical models demonstrate desired frequency selectivity akin to the capability of a biological basilar membrane. Subsequently, a proof-of-concept model of the proposed structure is custom-fabricated through standard photo- and soft lithography techniques using Polyvinylidene Difluoride (PVDF), gold, and Polydimethylsiloxane (PDMS) materials. Finally, the fabricated artificial basilar membrane that is intended to be used as a broad band sensor, is experimentally characterized using a custom-built acoustic exciter, and its effective performance is validated within the frequency range of 3 kHz to 8 kHz.

A high percentage of failures in sensors and devices employed in harsh industrial environments and airborne electronics is due to mechanical vibrations and shocks. Therefore, it is of paramount importance to test equipment reliability and ensure its survival in long missions in the presence of physical fluctuations. Traditional vibration testbeds employ unidirectional acoustic or mechanical excitations. However, in reality, equipment may encounter uncoupled (unidirectional) and/or coupled (multi- directional) loading conditions during operation. Hence, to systematically characterize and fully understand equipment's behavior, a testbed capable of simulating a wide variety of vibration conditions is required. The primary objective of this work is design, fabrication, and testing of AEVE 3D, an Acousto Electrodynamic three-dimensional (3-D) Vibration Exciter, which simulates coupled and decoupled (with unpowered arms) 3-D acoustic and/or 3-D mechanical vibration environments. AEVE 3D consists of three electromagnetic shakers (for mechanical excitation) and three loud speakers (for acoustic excitation) as well as a main control unit that accurately calculates and sets the actuators' input signals in order to generate optimal coupled and decoupled vibrations at desired frequencies. In this paper, the system's architecture, its mechanical structure, and electrical components are described. In addition, to verify AEVE 3D's performance, various experiments are carried out using a 3-D Piezoelectric energy harvester and a custom-made Piezoelectric beam.

Through an alternative paradigm, a predictive design of a Dirac-like point is introduced in a linear periodic metamaterial for the spatial guidance of acoustic waves. Dirac conelike dispersion at the Г point (for $\overrightarrow{\mathrm{k}}=0$ ) in a Brillouin zone is called a “Dirac-like cone,” which seldom occurs due to accidental degeneracy. However, a deaf band-based predictive model shows incredible potential to achieve an engineered Dirac cone at a predictive pivoted frequency. A targeted Dirac cone at a higher frequency is carried out in this article validating the orthogonal energy transport in a spiral pattern. The dominance of asymmetric deaf band modes triggers total internal reflection and guiding of acoustic waves inside phononic crystals. To elucidate the versatility of this methodology, experimental validation of orthogonal wave transport is presented.