Characterisation of medical microfluidic systems regarding fast changing flow rates using optical front tracking methods

•In this work two optical front tracking methods have been applied.•Dynamic properties of thermal flow sensors were characterised.•Pulsating flow rates of different micro pumps were measured with sample rates of 1 kS/s and 10 kS/s.

The presented optical flow metering methods are appropriate to characterise the dynamic properties of microfluidic systems. The dynamic behaviour of clinical or medical devices, micro pumps and flow sensors based on thermal methods were investigated. The Camera-System covers a flow range from 50 nl/min to 500 µl/min. The uncertainty is less than 4%, sample rates up to 5 kS/s. The Displacement-Sensor-System covers a flow range between 100 µl/min and 50 ml/min. The uncertainty is less than 3% at sample rates up to 49 kS/s. It was shown that measuring pulsating flow rates with thermal flow sensors is possible, but the signal is low pass filtered. The low pass behaviour is determined by the thermal properties, thermal resistance and heat capacity, of the flow channel. But the mean flow rate was always measured properly. The fluidic properties of two different types of micro pumps were examined and characterised exemplary.