Three-dimensional non-close-packed arrays formed by soft PMMA spheres

Polymethyl methacrylate (PMMA) spheres synthesized at boiling temperature were used to fabricate non-close-packed arrays by vertical lifting method. Scanning electron microscope (SEM) images demonstrated that these spheres could stack with square lattices parallel to the substrate and the neighboring spheres in the same layer were not contacted each other. In addition, the distance between the spheres can be controlled by thermal treatment. The method gave a new approach for extending the possibility of nanospheres lithograph and the creation of photonic band gap materials.