Single-Use System Integrity III: Gas Flow Rate through Laser-Drilled Microchannels in Polymeric Film Material

This study investigated the gas flow mechanism through microchannels in a flexible single-use packaging system composed of multilayer plastic film. The relationship was studied between the gas flow rate and several parameters, which included the differential pressure as an external parameter and channel geometries as internal parameters. Based on the results of this study, empirical formulas were derived that show the different dependency of the parameters for each gas flow regime. It was found that these formulas are suitable for calculating the size of a leak in a defective product directly from the corresponding flow rate. The test samples used were 50 mm patches of an ethylene vinyl acetate multilayer film (300 μm and 360 µm thick) and a polyethylene multilayer film (400 μm thick). Artificial leaks in a range of sizes from 2 μm to 100 μm were laser drilled into the center of each patch. The patches were assembled in a filter holder to form a leak-tight seal and were mounted on the test setup. The test setup included the flow measurement device and the pressure controller that used compressed air to produce a certain differential pressure. Various differential pressures were applied to each test unit to cover the whole range of desired use-case conditions. To understand and interpret the effect of the physics and geometry of the microchannels on flow rate measurement, the microscopic investigations performed in our previous study were used. All measurements were carried out under laboratory temperature conditions of 20°C.