Abstract
Modelling of single cellulose fibres is usually performed by assuming homogenous properties, such as strength and Young’s modulus, for the whole fibre. Additionally, the inhomogeneity in size and swelling behaviour along the fibre is often disregarded. For better numerical models, a more detailed characterisation of the fibre is required. Herein, we report a method based on atomic force microscopy to map these properties along the fibre. A fibre was mechanically characterised by static colloidal probe AFM measurements along the longitudinal direction of the fibre. Thus, the contact stress and strain at each loading point could be extracted. Stress–strain curves were be obtained along the fibre. Additionally, mechanical properties such as adhesion or dissipation were mapped. Local variations of the effective fibre radius were recorded via confocal laser scanning microscopy. Scanning electron microscopy measurements revealed the local macroscopic fibril orientation and provided an overview of the fibre topography. By combining these data, regions along the fibre with higher adhesion, dissipation, bending ability and strain or differences in the contact stress when increasing the relative humidity could be identified. This combined approach allows for one to obtain a detailed picture of the mechanical properties of single fibres.Graphic abstract
Highlights
Cellulose-based papers have promising applications in areas such as electronics, sensor technology, microfluidics, and medicine (Bump, 2015; Delaney et al 2011; Hayes and Feenstra 2003; Liana et al 2012; Ruettiger, 2016)
A cotton linter fibre, which consists of 95% cellulose, served as the model system (Mather and Wardman 2015; Young and Rowell 1986), and the results indicate that the mechanical properties of the fibres strongly varied along the longitudinal direction of the fibre, in a humid environment
By combining Confocal laser scanning microscopy (CLSM) and AFM colloidal probe bending measurements, we developed a mechanical image of a single fibre and related the mechanical behaviour and the increase in RFibre for each regions of interest (ROIs)
Summary
Cellulose-based papers have promising applications in areas such as electronics, sensor technology, microfluidics, and medicine (Bump, 2015; Delaney et al 2011; Hayes and Feenstra 2003; Liana et al 2012; Ruettiger, 2016). Before paper can be used as a substrate material for these technologies, an understanding of how the mechanical properties depend on the structure and variations and inhomogeneities of single cellulosic fibres must be improved. Cellulose is a naturally occurring material that is abundant and renewable. It is the most important raw material in the paper-making industry. In pulping and paper making, the flexibility of a single fibre plays an important role. Flexibility is responsible for quality during sheet formation and production of types of papers (Persson et al 2013). To control this process, characterisation of the processed fibres is important
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