Lamberti et al. investigated the effect of PDMS composition, i.e., the ratio between PDMS oligomers and curing agent, on its permeation properties to air. They focused on three membrane compositions: 5:1, 10:1, and 20:1 weight ratio of polymer base to curing agent and observed that increasing the polymer/curing agent ratio, the permeability of the membrane increases. This is due to a lower amount of cross-linked PDMS oligomers which allows an easier and faster diffusion of gases across the membrane. However, a PDMS membrane with a lower curing agent ratio is also more elastic, sticky, and harder to handle and integrate into a microfluidic device.