Abstract
We propose a switchable filter composed of transmutable array using shape memory alloys (SMA). It could exhibit a temperature induced morphology change spontaneously like the biological excitability, acting as a shutter that allows the incident energy to be selectively transmitted or reflected with in excess of 12dB isolation at the certain frequencies for both polarizations. Equivalent circuit models describe the operational principle qualitatively and the switching effect is underpinned by the full-wave analysis. A further physical mechanism is shown by contrasting the distributions of electric field and surface current on the surface at the same frequency for the two working modes. The experimental results consist with the theoretical simulations, indicating that the metasurface could serve as one innovative solution for manipulating the electromagnetic waves and enlighten the next generation of advanced electromagnetic materials with more freedom in the processes of design and manufacturing.
Highlights
Metamaterials are an engineered class of materials which exhibit properties not typically found in nature
Compared with the conventional frequency selective surface (FSS), the frequency response of a switchable filter can be varied with time under the control of active devices incorporated into the unit cells, such as PIN diodes[13,14,15,16] and microelectromechanical systems (MEMS) switches,[17,18] or by utilizing a ferrite,[19] liquid crystal[20] or elastomer[21] as the substrate
To better understand the impact of morphology switching of the unit cell on the transmission characteristic, we can gain some insight into the variations of the electric field strength and surface current distribution on the surface at resonance frequency as shown in Fig. 7 and Fig. 8 when the value of α is different for both polarizations
Summary
Metamaterials are an engineered class of materials which exhibit properties not typically found in nature. All the attempts exhibit unavoidable drawbacks including insertion losses, pass-band fluctuations, unwanted resonances, high cost, complexity of the fabrication and lack of the design flexibility. Another kind of method is the use of structurally reconfigurable metamaterials,[22,23,24] but the previous works are operated under extreme temperatures and the modulation depths are not good enough. The excitability of living organism, we design and fabricate a contrasting class of switchable spatial filter based on a transmutable metasurface using SMA. The highly controllable mechanism of engineering and manipulating the transmission characteristic of the transmutable metasurface will be a valuable reference for the application in engineering development
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