| Popis: |
The use of microrobotics in high throughput and precise characterization of objects at microscale has been noticeably increased during recent years. Microrobotics has provided a significant added value to multiple realms e.g. biomedical research, bio-based industry, microassembly of miniature products, etc. Recently, the use of microrobotic technology in paper industry has been also commenced for measuring properties at the single fibre level. There is a large interest in the measurement of different loading modes of individual fibre-fibre bonds in pulp and paper/board industry. Among the four different modes of loading, it would be desirable for papermaking companies and paper converting companies to obtain the Z-directional strength of pulp and paper. Indeed, the Z-directional properties affect compressive properties, and accordingly the performance of structural paperboard products. Several methods have been developed to measure the Z-directional strength at a handsheet level; however, there is not any reported device capable of the Z-directional fibre-fibre bond strength measurement at a fibre level. This thesis work presents a novel method for the experimental evaluation of the Z-directional bond strength using microrobotics and a Polyvinylidene fluoride (PVDF) film microforce sensor. Due to the special dynamics of PVDF microforce sensors, the effect of the deformation rate on the performance of the sensor is studied. The Z-directional fibre-fibre bond strength experiments have been performed successfully for unrefined and refined bleached softwood Kraft pulp fibres. Besides, paper scientists are interested in microfibril angle changes during and after application of the Z-directional force. Indeed, there is interest in simultaneous measurement of microfibril angle and mechanical properties such as Z-directional bond strength. To address this need, a microfibril angle measurements system based on microscopic transmission ellipsometry is developed and integrated to the microrobotic platform. The results from both Z-directional bond strength and microfibril angle measurement are promising. In summary, the first concept for simultaneous measurement of microfibril angle and mechanical properties such as Z-directional bond strength at the individual fibre level is developed during this thesis work which has a high practical impact on the fibre characterization research field. |
