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

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 50nl/min to 500µl/min. The uncertainty is less than 4%, sample rates up to 5kS/s. The Displacement-Sensor-System covers a flow range between 100µl/min and 50ml/min. The uncertainty is less than 3% at sample rates up to 49kS/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.