Figure 11.

(A) Schematic illustration of fabrication steps for freestanding silk opal using a close-packed PMMA colloidal crystal as a template. (B) Photograph of a 2.5 × 1.5 cm freestanding silk film with patterned inverse opals. Corresponding SEM images show the green (left) and blue (right) silk opals. Scale bars, 500 nm. (C) Glucose refractive index sensing for the silk film with patterned inverse opals with lattice constants of 240 nm, showing reflectance spectra for different concentrations of glucose (0%, 5%, 12.5% and 21.25%) [55].