Mechanical Terahertz Modulation by Skin-Like Ultrathin Stretchable Metasurface.

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.