Characterizing the Parameter Space of an Oxygen Gradient between Hypoxic and Normoxic Gas Networks

Microfluidics has been growing in popularity for lab-on-a-chip applications and is a versatile platform for biologic and cellular studies. Microfluidics is used because of its ability for tight oxygen control and flow properties that emerge at the micro-scale. Oxygen gradients are found in physiological systems, but are difficult to generate in the laboratory environment. Microfluidics offers a platform to create stable and physiologically accurate oxygen gradient environments that can be used for extended periods of time. However, there is still much research that needs to be done in understanding and achieving precise manipulation of these devices. One example is to study gas control in hypoxic and normoxic dual condition environments. We explore the effect of specific design manipulations such as channel width, gap spacing, and others on the incidence of the oxygen gradient profiles in microfluidic devices. The hypothesis was that the changes in resistance in the channels created by different parameters would result in substantial differences in the oxygen gradient profiles observed when they are run in a dual condition environment. We obtained data through extensive experiments, and observed that the oxygen gradient profile is the same in very different designs. Serpentine channel device designs as well as a low resistance open-well channel designs are observed to find the same gradient slope in each, even with slower flow rates. These results suggest that the resistance may not be the driving factor in the generation of oxygen gradients and that the profile cannot be changed on the microscale. Although the results are contrary to what was expected, we show that the implications presented in these sets of experiments aid in furthering the understanding of microfluidics and the effect of manipulation on gas flow studies.