Toda Ohira and Ikeda in their article 'Micro-gas analysis system microGAS comprising a microchannel scrubber and a micro-ï¬uorescence detector for measurement of hydrogen sulï¬?de' spin PDMS to create a thin membrane for use as a gas permeable membrane. They have a plot of spin speed vs PDMS thickness. For a thickness of about 10 um they use a spin speed of 5000 rpm. Good luck Dr Matt Davies Post-Doctoral Research Assistant Science & Technology Research Institute University of Hertfordshire College Lane HATFIELD AL10 9AB UK e : m.davies@herts.ac.uk