skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Enhancing Adaptable Topological Wave Bandwidth in Piezoelectric Metamaterials via Circuitry and Lattice Symmetry Control
Recently, an electromechanical metamaterial with integrated resonant circuit elements was developed that enables on-demand tailoring of the operating frequency and interface routes for topological wave transmission. However, limitations to the operating frequency region still exist, and a full exploration of the adaptive characteristics of the topological electromechanical metamaterial has yet to be undertaken. To advance the state of the art, this study investigates the ability to enhance the range of operating frequencies for topological wave transmission in a piezoelectric metamaterial by the reconfiguration of lattice symmetries and connection of negative capacitance circuitry. In addition, the capability to modify the interface mode localization is analyzed. The plane wave expansion method is utilized to define a working frequency region for protected topological wave transmission by evaluating a local topological charge. Numerical simulations verify the existence of topologically protected interface modes and illuminate how the localization and shape of these modes can be altered via external circuit parameters. Results show that the reconfiguration of the lattice structure and connection to negative capacitance circuity enhances the operating frequency bandwidth and interface mode localization control, greatly expanding the adaptive metamaterial capabilities.  more » « less
Award ID(s):
1661568
PAR ID:
10299733
Author(s) / Creator(s):
;
Date Published:
Journal Name:
ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems
Page Range / eLocation ID:
SMASIS2020-2292
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. null (Ed.)
    Many engineering applications leverage metamaterials to achieve elastic wave control. To enhance the performance and expand the functionalities of elastic waveguides, the concepts of electronic transport in topological insulators have been applied to elastic metamaterials. Initial studies showed that topologically protected elastic wave transmission in mechanical metamaterials could be realized that is immune to backscattering and undesired localization in the presence of defects or disorder. Recent studies have developed tunable topological elastic metamaterials to maximize performance in the presence of varying external conditions, adapt to changing operating requirements, and enable new functionalities such as a programmable wave path. However, a challenge remains to achieve a tunable topological metamaterial that is comprehensively adaptable in both the frequency and spatial domains and is effective over a broad frequency bandwidth that includes a subwavelength regime. To advance the state of the art, this research presents a piezoelectric metamaterial with the capability to concurrently tailor the frequency, path, and mode shape of topological waves using resonant circuitry. In the research presented in this manuscript, the plane wave expansion method is used to detect a frequency tunable subwavelength Dirac point in the band structure of the periodic unit cell and discover an operating region over which topological wave propagation can exist. Dispersion analyses for a finite strip illuminate how circuit parameters can be utilized to adjust mode shapes corresponding to topological edge states. A further evaluation provides insight into how increased electromechanical coupling and lattice reconfiguration can be exploited to enhance the frequency range for topological wave propagation, increase achievable mode localization, and attain additional edge states. Topological guided wave propagation that is subwavelength in nature and adaptive in path, localization, and frequency is illustrated in numerical simulations of thin plate structures. Outcomes from the presented work indicate that the easily integrable and comprehensively tunable proposed metamaterial could be employed in applications requiring a multitude of functions over a broad frequency bandwidth. 
    more » « less
  2. A substantial challenge in guiding elastic waves is the presence of reflection and scattering at sharp edges, defects, and disorder. Recently, mechanical topological insulators have sought to overcome this challenge by supporting back-scattering resistant wave transmission. In this paper, we propose and experimentally demonstrate a reconfigurable electroacoustic topological insulator exhibiting an analog to the quantum valley Hall effect (QVHE). Using programmable switches, this phononic structure allows for rapid reconfiguration of domain walls and thus the ability to control back-scattering resistant wave propagation along dynamic interfaces for phonons lying in static and finite-frequency regimes. Accordingly, a graphene-like polyactic acid (PLA) layer serves as the host medium, equipped with periodically arranged and bonded piezoelectric (PZT) patches, resulting in two Dirac cones at theKpoints. The PZT patches are then connected to negative capacitance external circuits to break inversion symmetry and create nontrivial topologically protected bandgaps. As such, topologically protected interface waves are demonstrated numerically and validated experimentally for different predefined trajectories over a broad frequency range. 
    more » « less
  3. Electromechanical metamaterials have been the focus of many recent studies for use in simultaneous energy harvesting and vibration control. Metamaterials with quasiperiodic patterns possess many useful topological properties that make them a good candidate for study. However, it is currently unknown what effect electromechanical coupling may have on the topological bandgaps and localized edge modes of a quasiperiodic metamaterial. In this paper, we study a quasiperiodic metamaterial with electromechanical resonators to investigate the effect on its bandgaps and localized vibration modes. We derive here the analytical dispersion surfaces of the proposed metamaterial. A semi-infinite system is also simulated numerically to validate the analytical results and show the band structure for different quasiperiodic patterns, load resistors, and electromechanical coupling coefficients. The topological nature of the bandgaps is detailed through an estimation of the integrated density of states. Furthermore, the presence of topological edge modes is determined through numerical simulation of the energy harvested from the system. The results indicate that quasiperiodic metamaterials with electromechanical resonators can be used for effective energy harvesting without changes in the bandgap topology for weak electromechanical coupling. 
    more » « less
  4. Mode couplings associated with elastic wave propagation through three-dimensional multiplex structures, as manifested by asymmetric eigenmodes and dissipation, determine the efficiency of electromechanical structures. As a result, it is critical to predict electroelastic symmetric modes such as thickness expander and radial modes, as well as asymmetric flexural modes, while accounting for material losses. Multiplex electromechanical structures include multi-layered through-wall ultrasound power transfer (TWUPT) systems. Physical processes that support TWUPT include vibrations at a transmitting/acoustic source element, elastic wave propagation through a barrier and coupling layers, piezoelectric transduction of elastic vibrations at a receiving element, and spatial resonances of the transmitting and receiving elements. We investigate mode couplings in an optimized modal TWUPT system, including their physical origins, models used to describe them, and regimes of weak and strong couplings. The system layout optimization is defined in terms of size (volume), operating frequency, and matching circuit load optimization. A computational model is developed and utilized in conjunction with experimental modal characterization to highlight the impact of eigenmode features on optimization results. Several behavioral modes are identified and analyzed. The interaction of symmetric radial and asymmetric flexural modes causes the system damping to increase and the device's overall efficiency to decrease. The electromechanical coupling factor value is likewise reduced as a result of this. Such occurrences are explained by the flow of energy between modes as they interact. The present work also proposes design guidelines to improve the performance of TWUPT systems based on exploiting inherent physical phenomena. 
    more » « less
  5. In this paper we conceptualize electroacoustic transistors based on topologically protected interface states in a reconfigurable valley-Hall topological insulator. Using piezoelectric media and active shunt circuits, we numerically model the spatial inversion symmetry breaking in a unit cell to produce topological bandgaps. These gaps are known to host robust modes for wave propagation along an interface. We use two such modes to design a transistor where the wave propagation in one topological channel switches on or off a second topological channel between a source and receiver elsewhere in the structure. Multiple such transistors may be combined to develop logic gates. Further, we develop and simulate the behavior of an electronic circuit which enables the transistor action. Our design opens a pathway to novel wave-based devices which may find applications in structure-based computing, as hybrid multiplexers in communication devices, and as structural switches or embedded sensors in robotics and internet of things. 
    more » « less