With the continuous advancement of biocompatible, biodegradable and non- toxic materials for hydrogels, their usage has greatly expanded in the fields of medicine and pharmaceuticals. The importance of those materials, combined with their high sourcing cost, invokes the need for characterization methods which consume less material for samples and are non-destructive to the sample. Meanwhile, an important set of properties that are directly connected to their application and maintenance in an organism are the rheological properties of such materials.
In my master’s thesis, I studied the effects of ageing and weight percentage of the dispersed phase in a set of nanofibrilated cellulose suspensions, using a comparison of two methods – a rheometer, which measures the material in bulk quantities (in the range of milliliters), and optical tweezers, which is a method of microrheological measurement (in the range of micro and nanoliters). Based on the experiments and the fitting of the experimental data, I found out that the ageing of the systems and the weight percentage of the dispersed phase has an influence on the rheological properties of the systems. Further, I have found that the results from both methods were not comparable on the same timescale. However, I have also found out that microrheological measurements using optical tweezers provide complementary information on the rheological and viscoelastic behavior of heterogeneous systems related to changes in the suspension microstructure, on a different timescale, which is not possible to be recorded by using a rheometer to characterize the systems.
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