Microgravity Experiments on Bubble Removal in the Hydrodynamic Focusing Bioreactor - Space (HFB-S)
The Hydrodynamic Focusing Bioreactor-Space (HFB-S) is being developed as a possible replacement for the Rotating Wall Perfused Vessel (RWPV) bioreactor currently planned for use on the International Space Station (ISS). The HFB-S is being developed with the ability to remove gas bubbles that may inadvertently enter the system during long duration experiments (approx. 1-3 months). The RWPV has been used in the past with great success on Shuttle flights and Mir missions, but has occasionally experienced problems with gas bubbles entering the fluid-filled vessel. These bubbles are harmful to the cell science, and bubble removal in the RWPV is problematic. The HFB-S has an access port on the rotation axis that allows for bubble removal under specific operating conditions without detrimentally affecting the cell tissue. Experiments on bubble removal with the HFB-S were conducted in the microgravity environment on NASA's KC-135 Reduced Gravity Aircraft. The first set of flights provided useful data on bubble trajectories that are validating computational predictions. The second set of flights free-floated the apparatus and tested the most recent configuration of the bioreactor while focusing on the bubble removal process itself. These experiments have shown that gas bubbles can successfully be driven to the removal port and purged in microgravity. The last day's experiments had an excellent microgravity environment due to calm air, and the experience gained in previous flights allowed successful bubble removal 18 out of 35 tries, remarkable given the microgravity time constraints and g-jitter on the KC-135.