Micro- and nano-robotic manipulation and characterisation of paper-making fibres and its components

Although huge quantities of paper fibres are analysed in automated machines for their dimensional properties (length, width, and wall thickness), these machines are restricted to certain test procedures. However, in recent years, it became of greater interest to study the basic reactions of wood fibres to process influences throughout the mechanical pulping process with the aim of understanding the interaction of single fibre development and specific energy consumption. Understanding the occurrence and development of morphological features would enable e.g. revising the energy-intensive mechanical pulping process towards more efficient energy use and higher raw material exploitation. Such morphological features are for example fibre wall degradation/delamination, outer fibre wall cracking with slit propagation, dislocations, or fibrillation in both mechanical and chemical pulp fibres. In the case of (large) dislocations in chemical pulp fibres, the less ordered or more open amorphous cellulose structure is more vulnerable to chemical, mechanical or enzymatic attacks. To understand, where in a fibre the highest effect occurs and how it develops with certain treatments is another reason to study single fibres instead of collecting average values. Three different nanorobotic systems were used inside scanning electron microscopes (SEM) for visual inspection of the manipulations. Low-pressure experiments were performed in a Quanta 600 of FEI, Netherlands, with a tungsten cathode as electron source. Other experiments were conducted in a LYRA 3 FEG / XMH of Tescan, Czech Republic, which works with a field emission gun and is also equipped with a focused ion beam (FIB) column. A microrobotic platform to manipulate individual paper fibres has been developed at the Department of Automation Science and Engineering of Tampere University of Technology. The platform is used to manipulate and sort individual paper fibres (IPF) to prepare the samples for visualisation in a SEM. The platform operates with two microgrippers to grasp IPFs disintegrated in deionized water. An additional self-tailored probe is used to place the IPFs on SEM sample holders. Afterwards, the samples are transferred into the SEMs for manipulations. Different manipulation techniques were performed including fibre gripping, pick-and-place, and fibre slicing. The gained experience was used to perform a number of preparing steps and characterisation experiments which are not yet available in larger scale applications in the presented resolution, e.g. testing the compressibility of single fibres with force feedback and quantify this property. Furthermore, the use of the focused ion beam (FIB) in the Tescan Lyra as a charged particle manipulation of the fibre was tested. By cross-cutting the fibre and microrobotically removing the cut-out fibre segment it was easily possible to visualise the cross-section of the fibre. Additionally, the FIB was used to deposit metallic markers on the fibre surface and some deposition parameters were determined.