Aflat tissue engineered skin (thickness 2.3 mm) is attached to the bottom of a dish and cultured with cell media atop it (which has an oxygen concentration of 0.15 mol/m3). the diffusivity of oxygen in the skin is 3.4 e-9 m2/s, and according to experiments that you’ve performed, you want to make sure that the concentration of oxygen in the device doesn’t fall below 0.060 mol/m3. (below that concentration harms the cells.)