Visualization and measurement of dissolved oxygen concentrations in hydrodynamic flow focusing

Oxygen is an important parameter with significant effect on cellular development and function. Based on microfluidics, laminar flow and hydrodynamic focusing provide ideal tools for the generation of controlled micro-environments and their application as stimuli to cells. In this paper we demonstrate, for the first time inside a microfluidic device, the generation and characterization of hydrodynamically focused streams with defined dissolved oxygen level. A solid-state oxygen sensor layer was integrated into a PDMS-based microchannel and calibrated. Several combinations of sample and buffer streams with concentrations ranging from 0 to 34 mg/L O₂ were generated and measured down to a sample stream width of 20 ¿m. The device has the potential to provide novel insights into cell biology and improve the relevance of in-vitro cell assays.