Experimental Soft Condensed Matter Group Harvard University, Prof. D. A. Weitz Cool Picture of the Moment

Both pictures show the same glass slide covered with a thin (~1μm) PMMA film. In the center a periodic pattern of holes has been created in the film using lithography. Since the lattice parameter of the pattern is similar to the wavelengths of visible light, constructive interference causes the structure to shine brightly if watched from a certain angle. The color depends on the orientation, for the interference occurs for a single wavelength only. Patterns like this can direct the growth of colloidal single crystals by acting as templates for the first layer of particles sedimenting from a suspension (see the cartoon inset).

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Past cool pictures...