Day 6

Real Experiment with a Flow Meter in a Setup with Pressure-driven Flow Control over 7 days

An experiment over 7 days has been executed with the pressure-driven flow control method with continuous monitoring of the flow rate. The liquid passed through different tubes and capillaries as well as perfusion head PH-8 controlled by the pressure control system P2CS with the pressure range -500/+500 mbar and a 16-channel fluid switch FS. Two different flow meters by Sensirion were successfully tested: 1000 µl/min and 80 µl/min.

We used silicone tubings with ID=2 mm between the single modules, however, to increase the hydrodynamic resistance of the flow path a PTFE tube with a very small ID was integrated at the end of the setup. That allowed to work with convenient pressure values over 200 mbar.

Additionally, we examined the change of the pressure in the system and, thus, the decrease of the flow rate over time, induced by the change of the water column in the storage and waste reservoir. The flow rate decreased by 18µl/min over 4 days (starting value: 100 µL/min, value at the end: 82µl/min), which can be compensated by the pressure control system.

After 4 days an automated refilling was executed, so there was no need to interrupt the experiment. In principle, by this method experiments can be carried out without time limitation.

The setup consisted of:

– pressure control system P²CS with the pressure range -500/+500 mbar

– mobile pressure and vacuum source PVS

– fluid switch FS

– perfusion head PH-8

– flow meters of Sensirion (1000 µl/min and 80 µl/min)

– storage reservoir: 1L laboratory bottle

– refilling reservoir