Mechanically Tunable Optical Response in Silicon Nanosphere Metasurface Fabricated via Bottom‐Up Process

Abstract Applications based on metasurfaces are often hampered by the limited scalability and real‐time tunability of lithographically produced samples (top‐down). Bottom‐up approaches that start from nanoparticle building blocks relax these constraints. Here, a large‐area mechano‐tunable metasurface composed of a square array of silicon nanospheres (Si NSs) is introduced. The metasurface is produced by capillarity‐assisted self‐assembly of size‐purified colloidal Si NSs that have Mie resonances in the visible and near‐infrared range. The collective response of Si NSs in the metasurface exhibits reflectance peaks originating from electric (ED) and magnetic dipole (MD) resonances of individual Si NSs. The resonance wavelengths are sensitive to the lattice constant and thus can be modulated in a wide wavelength range (≈130 nm) by external mechanical strain. At a proper strain level, the ED and MD lattice resonances spectrally overlap, resulting in destructive interference of the backward scattering light (lattice Kerker effect), which strongly suppresses the reflectance. The reflectance modulation is at a maximum of 45.9% and is reversible over 100 stretching‐releasing cycles. This suggests that the produced flexible metasurface can be a mechano‐tunable flexible optical component.