Statistical Analysis of Nanofiber Mat AFM Images by Gray-Scale-Resolved Hurst Exponent Distributions

Tomasz Blachowicz,Jacek Grzybowski,Tobias Böhm,Michał Koruszowic,Krzysztof Domino,Andrea Ehrmann

doi:10.3390/app11052436

Abstract

Two-dimensional structures, either periodic or random, can be classified by diverse mathematical methods. Quantitative descriptions of such surfaces, however, are scarce since bijective definitions must be found to measure unique dependency between described structures and the chosen quantitative parameters. To solve this problem, we use statistical analysis of periodic fibrous structures by Hurst exponent distributions. Although such a Hurst exponent approach was suggested some years ago, the quantitative analysis of atomic force microscopy (AFM) images of nanofiber mats in such a way was described only recently. In this paper, we discuss the influence of typical AFM image post-processing steps on the gray-scale-resolved Hurst exponent distribution. Examples of these steps are polynomial background subtraction, aligning rows, deleting horizontal errors and sharpening. Our results show that while characteristic features of these false-color images may be shifted in terms of gray-channel and Hurst exponent, they can still be used to identify AFM images and, in the next step, to quantitatively describe AFM images of nanofibrous surfaces. Such a gray-channel approach can be regarded as a simple way to include some information about the 3D structure of the image.

Highlights

Electrospinning finds nowadays more and more frequent application in preparing nanofibers with diameters in the range of few ten to some hundred nanometers
Our research demonstrates that while the distributions themselves are modified by such post-treatment steps, their characteristics remain and can be used to quantitatively describe atomic force microscopy (AFM) images of electrospun nanofiber mats
Image a was taken in the middle of the upper surface of a nanofiber mat, image b near the outer border of the upper surface, c in the middle of the lower surface and d near the outer border of the lower surface

Summary

Introduction

Electrospinning finds nowadays more and more frequent application in preparing nanofibers with diameters in the range of few ten to some hundred nanometers Such applications concern diverse polymers, polymer blends or polymers with embedded nanoparticles [1,2,3,4,5]. Such nanofiber mats can be used in a broad range of possible applications, from filters [6,7] and catalyzers [8,9] to tissue engineering and cell growth [10,11,12,13]. Other parameters, such as the pore size distribution, are often important, but less easy to measure [17,18].

Methods

Results

Conclusion