Abstract
The generalized Snell’s law (GSL) with phase discontinuity proposed based on the concept of a metasurface, which can be used to control arbitrarily the reflection and refraction of waves, attracts a growing attention in these years. The concept of abnormally deflecting the incident wave has been applied to the elastic field very recently. However, most of the studies on metasurfaces are based on passive materials, which restricts the frequency or the deflected angles always working in a single state. Here, we steer elastic SH wave propagation in an electrorheological (ER) elastomer with a structured meta-slab composed of geometrically periodic wave guides by exposing the slab to the programmed electric fields. The dependence of phase velocities of SH waves on the applied electric fields can make the phase shift under the form of a special function along the slab, which will control the refraction angles of the transmitted SH waves by the GSL. Accordingly we design the meta-slab theoretically and conduct corresponding numerical simulations. The results demonstrate that the structured meta-slab under the programmed external electric fields can deflect SH wave flexibly with tunable refraction angles and working frequencies, and can focus SH wave with tunable focal lengths. The present study will broaden the scope of applying adaptive materials to design metasurfaces with tunability.
Highlights
Metasurface which can be considered as a two-dimensional version of metamaterial is a hot topic in electromagnetic and acoustic engineering fields, for its superiority of compactness and simplicity in fabrication
Most of the recent researches on metasurfaces are based on passive material
ER elastomers can be considered as solid analogs of ER fluids with micro- or nano-sized polarizable particles dispersed and locked within the elastomeric matrix. These materials are intended to operate in an elastic regime with mechanical properties controlled by the application of electric fields
Summary
Metasurface which can be considered as a two-dimensional version of metamaterial is a hot topic in electromagnetic and acoustic engineering fields, for its superiority of compactness and simplicity in fabrication. ER elastomers can be considered as solid analogs of ER fluids with micro- or nano-sized polarizable particles dispersed and locked within the elastomeric matrix These materials are intended to operate in an elastic regime with mechanical properties controlled by the application of electric fields. We recheck the effect of the viscoelasticity of the ER elastomer on steering of SH waves and find the consistent conclusion with that of the existing study.[26] And in view of that, at higher frequencies, the shear storage modulus and loss modulus are independent of deformation frequency and the loss modulus is very small,[24] the viscoelasticity of the ER elastomer is ignored in the present work for simplicity following the previous researches.[24,25] Here, programmed electric fields are applied to the meta-slab to realize its tunability of deflecting the incident SH wave.
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