Microfluidic rheology: A new approach to measure viscosity of ceramic suspensions at extremely high shear rates

This paper describes the operation principles of a micro-scale rheometry equipment based on the technology of microchannels on a chip and compares it with a conventional macro-scale rotational rheometer. Both techniques are used for the study of different solutions and suspensions of ceramic particles with different saccharides, which are subjected to a wide variety of shear rates from their preparation to their processing and injection in plasma spraying processes. The results have shown a clear difference between the rheological values obtained between both equipment, clearly influenced by the different measurement method. However, the microfluidic technique has higher accuracy to characterise fluids at high shear rates and low viscosities, and the apparent shear thickening observed in rotational rheometry for low viscosity samples due to wall slippage is not observed. In contrast, the fine microchannels of are easily clogged in concentrated suspensions.