Fig. 4

Validation results of pH distribution controlled by dissolved CO₂ in the cell culture medium in the media channel. (a) Representative fluorescence microscopy images of cell culture medium containing uranine. The uniform CO₂ conditions were generated by supplying gas mixtures containing 5, 20, or 50% CO₂ to both gas channels and the stage incubator for reference. The CO₂ gradient was generated by supplying gas mixtures with 1% and 50% CO₂ to the left and right gas channels, respectively, and 5% CO₂ to the stage incubator. (b) Representative fluorescence intensity ratio \(\overline{I }/{\overline{I} }_{5}\) relative to 5% CO₂ condition. (c) Relationship between relative fluorescence intensity ratio and pH of the cell culture medium containing uranine. (d) CO₂ concentration and pH gradients generated in the media channels (mean ± S.D., n = 3). The variables c_L, c_R, and c_atm indicate the CO₂ concentration in the gas mixtures supplied to the left gas channel, the right gas channel, and the stage incubator, respectively.