Figure 1. Single grain of 2D particle assembly by the rubbing process and its diffraction colors.

(a) SEM image of a hexagonally-ordered polystyrene (PS) particle monolayer (1 μm in diameter). This particle monolayer was prepared by rubbing on a PDMS-coated glass slide (10 cm × 10 cm). (b) A magnified SEM image of the box in Figure 1a. (c, d) Photograph of the particle assembly diffraction on a black paper (c) and on a semitransparent half dome screen (d). White light was transmitted to the single grain monolayer perpendicularly through a hole; 1 cm for (c) and 4 cm for (d). The light diffracted from the (11) plane (20) plane was split into rainbow colors. Human eyes perceive different colors depending on the tilted angle (θ), azimuthal angle (φ), and the sample-to-eye distance.