AFM images in air and water of kraft pulp fibres

There is a need for techniques that provide new insights into the morpholog y and properties of surfaces of interest to the pulp and paper industry. At omic force microscopy (AFM) is one such technique that may be used to image surfaces under ambient conditions, or even immersed in fluids, at resoluti ons ranging from tens of microns down to fractions of a nanometre. Here, we show that unbleached kraft pulp fibre surfaces can be imaged by AFM, both in air and in water. Images range in size from tens of microns, showing kra ft fibres in a paper sheet, clown to a few nanometres, showing individual m icrofibrils detached from the pulp by beating. It is possible to follow dir ectly the changes in dimensions of fibres on wetting and drying. At higher magnifications, the microfibrillar structure of the cell wall surface is re adily imaged. Individual microfibrils generated by beating, display a range of dimensions down to less than 1.5 nm. Image quality and ultimate resolut ion are currently less than for some electron microscopic techniques, but t he usefulness of AFM is ensured by the ease of sample preparation and the a bility to image surfaces under ambient conditions.