We developed and applied a micropump for liquid flows of 0-150 nL/min. The operating principle of this pump is based on the Hagen-Poiseuille law. The main advantages of this pump are that an accurate continuous flow rate can be achieved, it is cheap to manufacture, easy to parallelize and easy to integrate in microliter plates. Experiments at different flow rates showed that the flow rate remained stable in time and the measured flow rates corresponded very well to the Hagen-Poiseuille law. The applicability of the pump for reproducible feeding of microbioreactors was shown in a fed-batch system with a simple chemical reaction. Thereby the Hagen-Poiseuille pump was connected to a microbioreactor with a working volume of 100 mu L The microreactor was filled with a H2SO4 solution which was fed with a Na2CO3 solution at a constant rate, while measuring the CO2 release on-line. This resulted in a stable CO2 production rate. Subsequently, the pump was successful applied to carry out anaerobic fed-batch fermentations of Saccharomyces cerevisiae in the microreactor system for periods up to 20 h. (C) 2009 Elsevier Ltd. All rights reserved.