Lacunarity exponent and Moran index : a complementary methodology to analyze AFM images and its application to chitosan films.

Abstract

In this work, we developed new scripts to calculate the lacunarity exponent and Moran’s index of Atomic Force Microscopy (AFM) images. The lacunarity exponent was estimated by combining the Otsu binarization and gliding-box algorithm, and Moran index was introduced to evaluate the surfaces’ spatial autocorrelation. Developed scripts were first validated using numerical simulation of self-similar fractal and self-affine isotropic

surfaces. Then, we successfully synthesized chitosan films with different glycerol con- centrations and used the lacunarity and Moran’s index for a thorough characterization.

The validation of the proposed scripts using simulated Sierpinski Carpets and 3D artificial surfaces showed promising potential for analyzing AFM images. Finally, the methodology application to AFM images of chitosan films suggested that lacunarity analysis and Moran index determination could complement thin films’ quality processing control.