Microfluidic chip for automated screening of carbon dioxide conditions for microalgal cell growth.

This paper reports on a microfluidic device capable of screening carbon dioxide (CO2) conditions for microalgal cell growth. The device mainly consists of a microfluidic cell culture (MCC) unit, a gas concentration gradient generator (CGG), and an in-line cell growth optical measurement unit. The MCC unit is structured with multiple aqueous-filled cell culture channels at the top layer, multiple CO2 flow channels at the bottom layer, and a commercial hydrophobic gas semipermeable membrane sandwiched between the two channel layers. The CGG unit provides different CO2 concentrations to support photosynthesis of microalgae in the culture channels. The integration of the commercial gas semipermeable membrane into the cell culture device allows rapid mass transport and uniform distribution of CO2 inside the culture medium without using conventional agitation-assisted convection methods, because the diffusion of CO2 from the gas flow channels to the culture channels is fast over a small length scale. In addition, automated in-line monitoring of microalgal cell growth is realized via the optical measurement unit that is able to detect changes in the light intensity transmitted through the cell culture in the culture channels. The microfluidic device also allows a simple grayscale analysis method to quantify the cell growth. The utility of the system is validated by growing Chlamydomonas reinhardtii cells under different low or very-low CO2 levels below the nominal ambient CO2 concentration.