Characterization of the oxygen properties of a hybrid glass chip designed for precise on chip oxygen control

Despite its relevance in several research fields, the regulation of dissolved gas concentration in microfluidic chips remains overlooked. Precise control of dissolved oxygen levels is of importance for life science applications, especially for faithfully replicating in vivo tissue conditions in organ-on-chips. The current methods to control oxygen on-chip rely on the use of chemical scavengers, on the integration of an additional gas channel or on the perfusion of a liquid pre-equilibrated at a set oxygen level. However, for precise oxygen control, these microfluidic devices must be made from gas-impermeable materials. In this regard, glass is a material of choice due to its complete impermeability, but its microfabrication often requires specific clean room processes. Here, we report a low-tech fabrication method for a hybrid glass chip, which involves assembling glass components using an adhesion process. To evaluate this chip's suitability for use under highly controlled oxygen conditions, we developed a two-step assessment protocol. This involved determining the time needed to reach a target oxygen level during perfusion and measuring the reoxygenation time following the cessation of flow. Based on a dual approach of simulations and experiments, we emphasized crucial adhesive properties such as oxygen diffusion and solubility and proposed a range of well-suited adhesive materials. Finally, we demonstrated the interest of this hybrid glass chip for on-chip cell culture and cell respiration measurements. This work paves the way for broader accessibility in producing low tech gas-tight microfluidic chips for diverse applications.