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Multiscale Multiphysics Analysis of Deformable Microwave Metasurfaces Under Large Deformations and Prototype Fabrication

Karimi Mahabadi, Rayehe | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54834 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Naghdabadi, Reza; Sohrabpour, Saeed; Goudarzi, Taha
  7. Abstract:
  8. Electromagnetic metamaterials are designed artificial materials with sub-wavelength resonant inclusions. They can exhibit extraordinary properties such as negative permittivity, negative permeability, and anomalous reflection/refraction. Metasurfaces are 2D counterparts of metamaterials. Here, we proposed a framework for the multiscale multiphysics analysis of deformable metasurfaces. Nonlinear mechanical analysis (Geometry and material behavior), periodic boundary conditions, homogenization, multiscale analysis, and electromagnetic analysis are implemented in this framework. Benefiting from the framework, we proposed a multifunctional hyperelastic structured surface that can generate various transparency patterns at microwave regime under applied mechanical deformations. The bottom-up design of such a surface requires a deep investigation of mechanical and electromagnetic behavior by taking advantage of analytical formulations, numerical simulations, and experimental measurements. Therefore, we proposed an original cost-effective technique to fabricate the structured surface. Moreover, using our custom-made setup, we experimentally captured its intriguing functionalities. Moreover, we studied the deformable metamaterials under various strains and revealed that for large deformations, the linear mechanical constitutive relation is unable to correctly predict the mechanical and electromagnetic responses of a deformable metamaterial. Moreover, it is also unable to correctly find the frequency region for the negative permeability. Furthermore, we showed the effects of two key factors on the tunability of deformable metasurfaces; the resonator geometry and substrate stiffness. In addition, we proposed a design for a hyperelastic structured surface using the Genetic Algorithm optimization method. This multiphysics, multifunctional, hyperelastic structured surface offers two simultaneous functionalities; tunability and switchability. Mechanical strains up to 16.8 % can continuously tune the resonant frequency of this structured surface from 11.8 GHz to 10.9 GHz. In addition to a big shift in the resonant frequency (7.6 %), this structured surface shows a considerable change in its scattering parameter S21. Applying an average strain of 2.7 % increases the scattering parameter S21 of this design at the undeformed resonant frequency by 46.5 dB and decreased the scattering parameter S21 at frequencies lower than the undeformed resonant frequency up to 49.3 dB. Taking advantage of the multiscale multiphysics framework, we revealed other capabilities of the structured surface, generating various transparency patterns. Concludingly, the proposed multiscale multiphysics framework is capable of analyzing the metasurfaces under uniform and non-uniform displacement fields. It opens a new window into designing and controlling the metasurface functionalities as it benefits from nonlinear mechanical analysis and considers the whole surface in the analysis instead of one unit cell
  9. Keywords:
  10. Metamaterial ; Metasurfaces ; Microwave ; Large Deformation ; Multi-Scale Analysis ; Deformable Structured Surface

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