Hereby presented is a microfluidic system, including a micro pump, an oxygenator and a cell culture chamber for perfusion controlled hypoxia assays. It consists of laser-structured polycarbonate (PC) foils and an elastomeric membrane which were joined together using thermal diffusion bonding. The elastomer forms an oxygenator element. The microfluidic system is characterized using non-invasive flow measurement based on micro-Particle-ImageVelocimetry (μPIV) and optical oxygen measurement utilizing the oxygen dependent fluorescence decay. Based on those experimental results and mathematical considerations, the oxygenator and mass transport phenomena within the microfluidic system can be described. This oxygen sensor, the micro pump, a controlling device and the gas mixture at the oxygenator forms a regulatory circuit to adjust the oxygen content in the cell culture chamber and helps to produce well-defined hypoxic conditions for the cells.