Probing of Nanoscale Friction and Mechanical Characteristics of Cotton Fiber’s Surface

Hosseinali Hosseinali,Thomasson Thomasson

doi:10.3390/fib7070064

Abstract

The surface topography and nanomechanical attributes of two samples of cotton fibers, namely, A and B, were characterized with various operation modes of an Atomic Force Microscope (AFM). The surface topography and friction images of the fibers were obtained in contact mode. The nanomechanical properties images—i.e., adhesion and deformation—were obtained in force tapping mode. The results indicate that the surface nanomechanical and nanoscale frictional properties of the fibers vary significantly between two samples. The plots of friction versus normal force of the fibers’ surface from both samples are fitted to the equation of single-asperity, adhesion-controlled friction. Nevertheless, within the range of the applied normal force, the friction curves of sample A surfaces show a characteristic transition phase. That is, under low normal forces, the friction curves closely conform with the Hertzian component of friction; after the transition takes place at higher normal forces, the friction curves follow Amontons’ law of friction. We demonstrated that the transition phase corresponds to a state at which the cuticle layer molecules are displaced from the fibers’ surface. The average adhesion force of the samples is consistent with the average friction signal strength collected under low normal forces.

Highlights

An Atomic Force Microscope (AFM) is a widely-used instrument to characterize the morphological, nanotribological, and nanomechanical properties of various surfaces [1]
Plant cells are naturally coated with an ultrathin extracellular membrane, collectively referred to as the cuticle layer
To better understand the origin of the frictional properties of cotton fiber assemblies, surface nanotribological properties of two cotton fiber samples were investigated at the nanoscale with an AFM

Summary

Introduction

An Atomic Force Microscope (AFM) is a widely-used instrument to characterize the morphological, nanotribological, and nanomechanical properties of various surfaces [1]. Applications of AFM in the nanoscale surface characterization of plant cells are expanding [2]. Plant cells are naturally coated with an ultrathin extracellular membrane (less than hundreds of nanometers thick), collectively referred to as the cuticle layer. The main functions of the cuticle layer are to preserve the physiological integrity of the cell and strengthen its overall structural stability [3,4,5]. The cuticle layer can be regarded as a multilayer, natural coating, primarily composed of biopolyester cutin, pectins, and lipid-derived compounds. The surface nanomechanical properties of the cuticle layer are of significant biological and technological importance. In the field of plant cell morphogenesis, it has been shown that the nanomechanical properties of the cuticle layer influence the cell’s shape changes and the growth rate [6,7,8]

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