Comparing flat and micro-patterned surfaces: Gas permeation and tensile stress measurements

Micro-patterning is a suitable method to produce structured membranes that display increased flux compared to flat membranes. In this work we studied the permeation of four different gases (nitrogen, helium, oxygen and carbon dioxide) through Kraton™ polymer (SBS) membranes. It is possible to cast a micro-patterned membrane with 25 μm high and 30 μm wide lines that has a thickness of 5 μm at its thinnest point. Using this micro-pattern, the experimental diffusive gas flux was increased up to 59% compared to non-patterned membranes with the same polymer volume. Finite element simulations confirm this enhancement. Selectivities are similar for both flat and micro-patterned membranes and in accordance with literature. Tensile stress measurements confirm that the micro-patterned membranes yield only limited loss in mechanical strength. Although only one material and geometry is explored here, this principle is generally applicable to all diffusion-driven processes.