First comparison of inline measurements of dynamic viscosity

Microfluidic devices are gaining importance in various fields of pharmacy, flow chemistry and healthcare. In the embedded microchannel, the flow rates, the dynamic viscosity of the transported fluids and the fluid dynamic properties play an important role. Various auxiliary functional components of microfluidic devices such as flow restrictors, valves and flow meters need to be characterised with liquids used in several microfluidic applications. However, calibration with water does not always reflect the behaviour of the fluids used in the different applications. Therefore, several National Metrology Institutes (NMI) have developed micro pipe viscometers for traceable in-line measurement of the dynamic viscosity of liquids used in flow applications as part of the EMPIR 18HLT08 MeDDII project. These micro pipe viscometers allow the calibration of any flow device at different flow rates and the calibration of the dynamic viscosity of the liquid or liquid mixture used under actual flow conditions. The traceability of the micro pipe viscometer, the validation of the stated measurement uncertainty with eight liquids as well as dynamic viscosity measurements with in-line sensors are presented in this paper.