Fabrication of large-scale monocrystalline silicon metasurfaces on flexible substrates

Flexible photonic devices based on metasurfaces exhibit characteristics such as ultra-thinness and light weight, enabling versatile applications across various surfaces, particularly in smart wearable devices, visible light communication, and conformal optics, etc. Among existing methods, direct flip transfer and stamp-assisted transfer are the two most prevalent processes. However, metasurfaces produced by these methods are typically embedded within a flexible substrate, constraining the dielectric environment of the metasurface. Moreover, conventional approaches often utilize materials like metal or amorphous silicon for nanoantennas, leading to unnecessary optical losses. In contrast, monocrystalline silicon offers a larger scattering cross-section and lower absorption loss, promising superior performance for photonic devices. Herein, we propose a method for fabricating reconfigurable, flexible centimeter-scale monocrystalline silicon metasurfaces. The process involves a polymer membrane containing monocrystalline silicon metasurface, followed by transferring the polymer onto a stretchable substrate (PDMS) utilizing water tension. The monocrystalline silicon nanoparticle arrays are affixed to the PDMS substrate via van der Waals force, with the surrounding area directly exposed to air. Further, photonic devices with upper and lower refractive index matching can be achieved by pouring PDMS. By adjusting the mechanical stretching of the photonic device, dynamic control of the light field can be realized.