Experimental Model of a Pore as a Valve Mechanism

Pores frequently occur in biological tissues. One such example is the gaps between the astrocyte endfeet that surround arteries in the brain. Flow through these pores often causes bending of the porous material. This raises questions: How does the pressure from fluid flow deform an elastic membrane? How does the newly deformed membrane, in turn, affect the flow? To address these questions, we used silicone sheets to make membranes with a single pore and subjected them to fluid flow. We were able to measure the flow rate at different pressures which allows us to estimate how the membrane has deformed. We found relatively good agreement between our results and simple estimates using plate bending and hydraulic resistance equations. Understanding how membranes deforming with oscillatory pressure act like a valve could help us explain the mechanism driving the flow of cerebrospinal fluid into the brain.