Milli, Micro and Nano Fluidics in Air-Lift Operated Tank for Culture of Animal Cell

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For the further improvement of bubble-driven airlift-operated tank for closed-system culture of animal cell, we studied both rising bubble behavior, and transport phenomena of cell and extra cellular matrix.It is highly required for the realization of the homogeneous bubbly flow that the most optimized bubble number density, i.e., bubble diameter and bubble mutual distance, should be determined. We observed the bubble motion in super purified water since the surfactant effects are essential for the bubble motion.It was found that the contact time of rising bubble with free surface was constant, and energy dissipation was very small. It was also found that the rising velocities of a pair of rising bubbles side by side in super purified water significantly decreased with bubble shape oscillations after the coalescence of bubbles.Wakes of rising bubbles were visualized by using silicone oil solution of photochromic dye, which was activated by illumation of UV light sheet. It was found that wakes of a pair of rising bubbles are playing the most important roles in the bubble coalescence and bouncing. It was also found that either double thread type or horse shoe type vortices, which are similar to those observed in the case of single rising bubble, were developed in the case of repetitive collision of a pair of bubblesWe also studied the relations between cell metabolism and transport phenomena in the extra cellular matrix (ECM). We visualized the diffusion of fluorescent labeled dextrin molecules in ECM constructed around cells by cell metabolism of animal cells which were seeded in agarose gel, in order to investigate transport phenomena around cells. It was found that ECM was constructed by the cell metabolism and that electrical effects are significant in transport phenomena in ECM.