A directional permeability membrane was designed, fabricated, and tested with the goal of allowing flow in one direction and preventing flow in the opposite direction. The membranes were constructed from two porous polyimide sheets with different thicknesses and bonded with double sided tape on the perimeter to create a separation in the range of 25-75 µm. Nine holes with diameter of 0.5 and 1 mm were cut in a polyimide sheet with thickness of 125 µm and four circular holes with diameter of 0.25 mm were cut in a polyimide sheet with thickness of 25 µm. The holes were cut in a square array with a distance of 2 mm from center to center.

The membranes were tested under pressure-driven water flow in the range of 0.01- 0.1 m H2O and flow rates were measured for two configurations: one with the thicker sheet upstream (forward direction) and one with the thinner sheet upstream (reverse direction). Results show that the ratio of forward/reverse flow rate varies in the range of 2.61 to 2.52×103, depending on the pressure head.

To have a better understanding of the membrane performance and flow characteristics, 3D numerical simulation was performed in ANSYS. The results of two-way fluid-structure interaction analysis are presented in the form of pressure as a function of mass flow rate and pressure as a function of membrane deflection. Simulations were performed at inlet pressure in the range of 0.01-0.1 m H2O. Results show that the closing pressure in reverse flow depends on the initial gap between the sheets and downstream sheet thickness.

Increasing the initial gap or the downstream sheet thickness will considerably increase the closing pressure in reverse flow. Moreover, the downstream sheet primarily changes the value of the mass flow rate in forward flow for the range of parameters tested. By decreasing the diameter of pores on the downstream sheet the value of mass flow rates decreases significantly while it slightly decreases the closing pressure.

Degree Date

Summer 8-3-2022

Document Type


Degree Name



Mechanical Engineering


David Willis

Subject Area

Bioengineering and Biomedical Engineering, Mechanical Engineering



Available for download on Sunday, August 04, 2024