The thermodynamic driving force for water diffusing into the hygro-elastomeric PDMS (H-PDMS) stems from the difference of the chemical potential of water between that of the surrounding phase and the inclusion. As expected, this force is highest when the surrounding phase is distilled water, but it decreases with the increase of the salinity of the aqueous phase. Thus, the film exhibits various degrees of swelling depending upon the salinity of the aqueous phase, which varied from zero to that of seawater in our experiments.