Date Approved

5-18-2023

Embargo Period

5-22-2023

Document Type

Thesis

Degree Name

M.S. Mechanical Engineering

Department

Mechanical Engineering

College

Henry M. Rowan College of Engineering

Advisor

Chen Shen, Ph.D.

Committee Member 1

Vinayak Ranjan, Ph.D.

Committee Member 2

Behrad Koohbor, Ph.D.

Subject(s)

Metasurfaces; Nanostructured materials

Disciplines

Materials Science and Engineering | Mechanical Engineering

Abstract

It has been demonstrated that metasurfaces with spatially asymmetric inner geometry exhibit unidirectional scattering effects, which can be used to control waves in a directional fashion. In this thesis, a planar Non-Hermitian elastic metasurface exhibiting unidirectional focusing of flexural waves is proposed. Asymmetrically loaded piezoelectric disks and metallic blocks comprise the unit cells. By using a negative capacitance shunting, a tunable material loss is embedded into the system. With suitable engineering of the induced loss profile, resonating building blocks are designed, which are capable of independently accessing unidirectional zero reflection. A planar metasurface is then created so that constructive interference can be achieved on one side only. That is realized by tuning the reflected phase. Numerical simulations demonstrate unidirectional focusing of the incident waves where a focusing effect is observed from one propagating direction, whereas zero reflections appear from the other. As each unit cell can be tailored independently by tuning the reflected phase and the loss, the designed metasurface endows flexibility in manipulating asymmetric elastic waves.

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