Numerical Study On The Influence Of Surface Roughness On Fluid Flow And Mass Transfer In A Flat-Plate Microchannel Bioreactor

Surface roughness exists in most microfluidic devices due to the microfabrication technique or particle adhesion. The present study has developed a numerical model based on Finite Volume Method to simulate the fluid flow and mass transfer in a flat-plate microchannel bioreactor with an array of rough elements uniformly placed on the bottom wall. Both semicircle and triangle roughness are considered to include more shapes of roughness elements. A monolayer of cells is assumed to attach to the base of the channels and consumes species from culture medium. The results show that the roughness size ratio (α) and the roughness distribution ratio (β) have direct and significant effects on fluid flow and mass transfer. The dimensionless parameters Peclet number(Pe)and Damkohler number(Da)can also influence mass transfer greatly. Although the two types of roughness have similar effects, at the same condition, the triangle roughness has larger effect on shear stress by showing higher dimensionless values at the channel base; the semicircle roughness has larger effect on mass transfer by showing lower dimensionless minimum base concentration$\bar C_{\min}$and higher dimensionless absorption rate(Δj%). However, it is important to ensure the lower maximum shear stress and the adequate minimum species concentration for cell growth in rough channels. Hence, if the maximum shear stress and minimum concentration in rough channels can satisfy the critical conditions for cell growth, rough channels would be better than smooth channels because of their lower shear stress at the flat-bed part and higher mass transfer efficiency. The results would provide guidance on the flow and perfusion requirements to avoid shear stress damage and solute depletion or toxicity during cell culture.