The Design and Analysis of a Micro Squeeze Flow Rheometer

This thesis describes the analysis and design of a micro squeeze flow rheometer. The need to analyse the rheology of complex liquids occurs regularly in industry and during research. However, frequently the amount of fluid available is too small, precluding the use of conventional rheometers. Conventional rheometers also tend to have the disadvantage of being too massive, preventing them from operating effectively at high frequencies. The investigation carried out in this thesis has revealed that current microrheometry techniques also have their own disadvantages. The proposed design is a stand-alone device capable of measuring the dynamic properties of nanolitre volumes of viscoelastic fluid at frequencies up to the kHz range, an order of magnitude greater than conventional rheometers. The device uses a single piezoelectric component to both actuate and sense its own position. Thorough analytical analysis of the microrheometer has been carried out. The capillary effects, including contact angle hysteresis, and viscoelasticity associated with the liquid has been combined with the dynamics and electrical response of the rheometer itself to form a complete and consistent model. The validity of the model has been proven through fabrication and testing of the rheometer.