Wrinkle‐Template Confinement of Kinetically Arrested Cellulose Nanocrystals for Sustainable Large Scale Reflection Gratings

Abstract Colors derived from reflection gratings are ubiquitous in nature, while artificial grating structures play an important role in various domains of optics. Motivated by creating an effective grating structure assembled only from simple materials available from renewable resources, cellulose nanocrystals (CNCs) are investigated as the dielectric grating material, and the polarized plane‐wave illumination is fully studied. By using wrinkled surfaces as template, all‐cellulose line arrays are assembled by template‐printing. The use of kinetically arrested CNC dispersions results in maintained shape during the pattern‐formation process: gratings of various wavelength and with heights 10 times larger than the width of a single CNC are fabricated. Within the produced films， ordered CNC arrangements are obtained after confinement drying as demonstrated by polarized optical microscopy. These films demonstrate significant reflection grating properties with up to ±3 diffraction orders easily resolved from the grating with a diffraction efficiency of 9% for the first order. The cut‐off ranges from visible region (508 nm) to the infrared region (1539 nm). Additional structures – with or without diffraction‐grating properties – can be printed onto the structured thin films. This work showcases a scalable and cost‐effective platform for realizing future developments in optical signal technologies with sustainable materials.