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Origami-inspired chiral metamaterials with tunable circular dichroism through mechanically-guided 3D assembly


 Chiral metamaterials with artificially engineered subwavelength structures can effectively couple incident waves and lead diverse electromagnetic responses to various circular polarizations. Here, we designed and fabricated an origami-inspired reconfigurable 3D chiral metamaterial, whose circular dichroism can be dynamically controlled by simple mechanical stretch of its bonded elastomer substrate. The chiral metamaterial was obtained from a patterned planar achiral metasurface through mechanically-guided 3D assembly based on the pre-strain approach, which ensures deterministic and uniform deformations for each building block during stretching. Numerical simulations and experimental observations were carried out to illustrate the deformation mechanism and the electromagnetic response of the metamaterials under the applied strain. It's shown that the transmissions and chiroptical activities can be continuously tuned from complete spin selectivity to partial spin selectivity when the applied strain increases. The maximum circular dichroism was experimentally measured as high as 0.98, which can be even adjusted to near zero by mechanical stretching. Our work demonstrated an easily operated and promising way to control the chirality of origami-inspired metamaterial in the microwave region, which can be further extended to the terahertz frequency biosensing, imaging and spectroscope.