GUVs with this composition were generated from the same master stock either by gentle or electroformation. The same master stock was also used to generate 100nm SUVs which were then ruptured onto NanoSIMS substrates to form continuous bilayers within the corrals of the patterned NanoSIMS substrate. Since these continuous bilayers are formed from hundreds of SUVs, the relative concentrations of 13 C18-DSPC and 2 H31-POPC should be more consistent than in SLB patches formed from the rupture of a single GUV. The measured 2 H -/ 13 C -ratio for 30 individual bilayer patches or 30 corrals containing continuous bilayers is shown in Figure . Based on the measured ratios, gentle hydration has the highest variation in relative concentration when compared to electroformation, with significance determined via F-test (the normality of each distribution assessed by F-test is further discussed in section 2 of the supporting information). Continuous bilayers formed from SUVs have the lowest variability. Replicate samples produced from films dried down from the same master stock also suggest that electroformation is more consistent than gentle hydration (Figure ).