On-chip Co₂ incubation of microfluidic cell culture devices by humidity/gas exchange through poly (dimethylsiloxane) membrane

We demonstrated an on-chip COO₂ incubation system suitable for microfluidic cell culture that does not need an external chamber or gas supply. A nested pair of reservoirs for liquids insulated by gas/vaporpermeable poly (dimethylsiloxane) (PDMS) enabled COO₂ incubation of media stored in the inner reservoir. This was achieved by only flowing heated sodium bicarbonate solution through the outer reservoir. The stabilization capability of temperature and pH was evaluated in situ with a miniature thermocouple and by absorption spectroscopy of phenol red, respectively. The temperature and pH were stabilized within the range of 37.0 ± 0.2°C and pH7.3 ±0.2 over at least 24 hours. This incubation capability was demonstrated through low-density microfluidic culture of CV-1 epithelial cells under an inverted microscope for three days.