Fig. 1
From: Structural color three-dimensional printing by shrinking photonic crystals
Heat shrinking induced colors of 3D-printed woodpile photonic crystals. a Schematic of the fabrication process. Left: woodpile photonic crystal written in commercial IP-Dip resist by two-photon polymerization at dimensions well above the resolution limit of the printer to prevent structures from collapsing. Right: after heat treatment, the dimensions of the photonic crystal are reduced below the resolution limit of the printer, and colors are generated. The colors change with different degrees of shrinkage. b Schematic showing one axial unit of the woodpile structure. axy and az denote the lateral and axial lattice constants, respectively. Tilted-view scanning electron micrographs (SEM) of a representative woodpile photonic crystal (c) before and (d) after heating. SEM images and corresponding brightfield reflection-mode optical micrographs of the woodpile photonic crystal before heating (e, i) and with shrinkages of 55% (f, j), 71% (g, k), and 78% (h, l). m Shrinkage of the woodpile photonic crystal heated at ~450 °C as a function of heating duration. Reflectance spectra of the woodpile photonic crystal n before heating and o after heating with 55%, 71%, and 78% shrinkage. Scale bars represent 10 μm
