Fig. 4. Cross sectional view of PPFC. Fluid enters through the inlet port and flows the chamber situated between two parallel plates. The chamber may be completely on one plate or distributed on the two plates. Surfaces studied for microbial activities are at the chamber on top or bottom, or on both. In most of PPFC designs the plates are made of substrate material used for the study and surface modifications are done to chamber surfaces. In some of the PPFC designs, the subject substrate is integrated into the chamber. Design adaptations were done with transparent plates to enable real-time monitoring of microbial activities inside. On average the chamber is 10 mm wide but has large variations in length. The chamber or the fluid volume typically 0.1–0.5 mm tall.