The modulation of terahertz plays a key role in realizing the tunable terahertz devices. The concept of flexible and stretchable electronics provides the possibility to dynamically modulate the terahertz with mechanical strain rather than additional electrical components. Here, the mechanical modulation of the terahertz transmission with a freestanding, skin‐like, and highly stretchable metasurface is experimentally illustrated. The stretchable metasurface is fabricated by merely constructing an Al/PI mesh film consisting of serpentine‐like unit cells, with total thickness of only 7 µm. With the flexibility realized by the extremely small thickness, the metasurface can be stretched, bended, and twisted, which provides the possibility to modulate terahertz transmission properties by the mechanical deformation of the metasurface. The terahertz time domain spectroscopy results indicate that the stretchable metasurface shows the band‐stop frequency selective effect and the transmission of the terahertz wave can be modulated from 0.15 to 0.5 with applied external tensile strains up to 28%, while only 3.4% of the shift of the resonance frequency is observed. The mechanisms of the metasurface and the relation between the modulation effect and the structural mesh parameters are also discussed with the electromagnetic simulations and the LC equivalent circuit model.

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Frequency selective surfaces (FSS) that can be tightly laminated to complex nondevelopable surfaces have a wide range of applications in many engineering areas. This paper presents a 3D flexible FSS prepared by mechanically guided 3D assembly, capable of being conformally adhered to complex surfaces, while maintaining stable frequency selective properties as well as transmission performance. The stretching strain applied to the prestrained ecoflex substrate can precisely tune and control the buckled 3D metal structures, which leads to the stretchability of the flexible FSS, introduces the increase of the inductance inside the metal cells, and expands the metal gap resulting in a reduction of the capacitance between the unit cells. The mutual correlation of capacitance and inductance ensures in the mechanism that the FSS transmission characteristics will not be significantly affected by the applied strain, as verified by calculations using the equivalent circuit method. Both the results obtained by the experiments and simulations indicate that the resonant frequency of the 3D flexible FSS is 5.7 GHz and the bandwidth at −10 dB is 0.94 GHz, while the resonant frequency shift will not exceed 0.45 Hz, and −10 dB bandwidth change will not exceed 0.32 GHz with applied strain of 17.8% in the ecoflex substrate. At the same time, the 3D flexible FSS maintains stable transmission performance for oblique incidence, with only 0.5 GHz frequency shift at 45° incidence. This stretchable flexible FSS with stable electromagnetic (EM) properties may find potential applications in EM shielding and spatial filtering due to its high flexibility, ready applicability, and cost‐effectiveness.

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Frequency selective surfaces (FSSs) with reconfigurable resonant frequency show significant potential for engineering applications. In this study, we propose a flexible FSS with a buckling dipole prepared by releasing the substrate pre-strain to buckle the locally adhered two-dimensional precursors, which can withstand large mechanical tensile deformation and change their resonant frequency during deformation. When the FSS is subjected to uniaxial tensile deformation, the capacitive effect between the adjacent buckled metal unit cells is significantly reduced due to the increase in the gap between the unit cells and period. This significant change in the equivalent circuit parameters due to the geometry change is highly beneficial for actively tuning the resonant frequency of the FSS. Electromagnetic (EM) experiments and simulations and equivalent circuit calculations are used to explore the EM tuning mechanism of the FSS and consistent conclusions are obtained. The results show that the FSS exhibits band-stop EM wave transmission characteristics with a resonant frequency of 6.1 GHz in the unstretched state and 21% uniaxial stretching strain can introduce a ~1.1 GHz increase in the resonant frequency. The corresponding parameter analysis shows that when the gap of the buckling dipoles in the width direction is reduced, the change in the resonant frequency caused by uniaxial stretching can be significantly increased, even to 2.5 GHz, which may help the FSS adapt to complex practical applications by tailoring the