Figure 6.

(a) Diagram of an indirect perfusion bioreactor. Indirect perfusion bioreactors are usually custom-made and support flow rates from 0.01 to 1 mL/min. Scaffold sizes of up to 14 mm in diameter are reported in the literature. (b) Diagram of a direct perfusion bioreactor. Direct perfusion bioreactors are usually custom-made to fit tightly around the scaffold. They usually require smaller flow rates than indirect perfusion bioreactors as here the flow is forced through the scaffold. This is due to the very small gap between the scaffold and the wall which requires more pressure to force flow through it and shifts the preferential flow through the scaffold. Maximum scaffold size reported in literature is 20 mm in diameter.³⁴