ABSTRACT
<p><b>OBJECTIVE</b>To analyze the forces of rotational wall vessel (RWV) bioreactor on small tissue pieces or microcarrier particles and to determine the tracks of microcarrier particles in RWV bioreactor.</p><p><b>METHODS</b>The motion of the microcarrier in the rotating wall vessel (RWV) bioreactor with both the inner and outer cylinders rotating was modeled by numerical simulation.</p><p><b>RESULTS</b>The continuous trajectory of microcarrier particles, including the possible collision with the wall was obtained. An expression between the minimum rotational speed difference of the inner and outer cylinders and the microcarrier particle or aggregate radius could avoid collisions with either wall. The range of microcarrier radius or tissue size, which could be safely cultured in the RWV bioreactor, in terms of shear stress level, was determined.</p><p><b>CONCLUSION</b>The model works well in describing the trajectory of a heavier microcarrier particle in rotating wall vessel.</p>