Self-assembly of microspheres at the air/water/air interface into free-standing colloidal crystal films

The air/water/air interface was employed as a platform for the self-assembly of colloidal microspheres, leading to planar and curved free-standing colloidal crystal films with sizes in excess of several square millimeters. In the resulting crystal films, few cracks were observed. The confinement of the air/water/air interface also led to a new type of cubic packing structure: stripes composed of cubic packed spheres were regularly separated by line defects, where spheres were hexagonally packed. Hence, the present colloidal crystallization method should be of interest in fundamental science and technical applications.