Beyond Static Culture
Static cell culture — cells sitting in a dish under a layer of medium — is limited by diffusion. For three-dimensional tissue constructs thicker than a few hundred micrometers, cells in the interior receive inadequate oxygen and nutrients. Perfusion bioreactors solve this by actively pumping medium through the scaffold pores, converting a diffusion-limited problem into a convection-driven one with dramatically improved mass transport.
Flow Through Porous Scaffolds
Medium flow through a porous scaffold obeys Darcy's law at low flow rates: the pressure drop is proportional to velocity, viscosity, and scaffold length, and inversely proportional to permeability. The superficial velocity (flow rate divided by cross-sectional area) determines both nutrient delivery and the shear forces that cells experience. This simulation lets you design the flow regime by adjusting bioreactor geometry and scaffold properties.
Shear Stress as a Signal
Fluid shear stress is not merely a side effect of perfusion — it is a powerful biological signal. Osteoblasts respond to shear by increasing alkaline phosphatase activity and mineralization. Chondrocytes upregulate collagen II and glycosaminoglycan production under moderate shear. Endothelial cells align with flow direction and express anti-inflammatory genes. The challenge is maintaining shear within the narrow window that promotes the desired cell response without causing damage.
Design Optimization
A well-designed bioreactor balances several competing requirements: sufficient flow for mass transport, appropriate shear for mechanotransduction, acceptable pressure drop for pump capacity, and uniform flow distribution to avoid dead zones. This simulation computes the key engineering parameters — superficial velocity, wall shear, pressure drop, and Peclet number — to help you design a bioreactor that meets all these requirements simultaneously.