Development of a novel fluid removal system to increase throughput and uniformity of fluid exchange in an open microfluidic culture platform

The Stacks platform is a reconfigurable open microfluidic cell culture device that enables integrated analysis of multi-culture systems. Effective utilization of this platform requires repeated fluid exchanges for culture maintenance as well as experimental interventions and analysis. The initial operating protocols of the Stacks platform incorporated conventional manual liquid exchanges for cell culture that are performed using standard single-channel pipettes to remove and replace individual 10 µL liquid droplets. While functional, this conventional Pipette Method (PM) for fluid exchange can be time-consuming and carries risk for intra- and inter-user variability in fluid exchange volumes. In order to improve the efficiency and reproducibility of ultra-low-volume fluid exchanges for the Stacks platform, we have developed a novel fluid removal device, called the Stacks Insert System (SIS), which is comprised of a base and insert component. In this manuscript, we describe the design of the SIS and compare its efficiency and reproducibility to fluid exchanges utilizing the conventional PM. We demonstrate that the SIS reduces fluid removal time by greater than 14-fold when compared to the conventional PM method while increasing uniformity of fluid volume removal, measured as total fluid volume removed per device. We propose the SIS protocol as an improved method to perform fluid removal for the integrated Stacks multi-culture platform. Furthermore, the principles of the SIS can be adapted to increase efficiency and reproducibility for other microfluidic and tissue chip platforms.