A novel approach to quantitatively assess the uniformity of binary colloidal crystal assemblies

Colloidal self-assembly into highly ordered binary systems represents a versatile and inexpensive approach to generate well defined surface topographical features with submicron resolution. In addition, the use of surface-functionalized particles where each particle bears a different surface functionality enables the generation of highly resolved surface chemical patterns. Such topographical, as well as chemical features, are of great interest in biomaterials science particularly in the context of investigating and controlling the cellular response. While colloidal crystals have been used to generate a wide range of surface patterns, it has not been possible until now to quantitatively describe the degree of uniformity within such systems. In the present work we describe a novel approach to quantitatively assess the uniformity within binary colloidal assemblies based on image processing methods, primarily the Circular Hough Transform and distance calculations. We believe that the methodology presented here will find broad application in the field of colloidal crystals to quantitatively describe the integrity and homogeneity of assemblies.