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Solvent exchangeis a simple process to form oil nanodroplets atsolid–liquid interfaces with well-defined location and morphology.In this process, a good solvent of the oil is displaced by a poorsolvent, leading to the nucleation and growth of oil droplets froma transient oversaturation at the mixing front. Our recent work hasshown that the final volume of the droplets is related to the flowconditions. In this work, we investigate the effects of the type andthe composition of solvents on the droplet formation under the sameflow conditions. Water nanodroplets were produced by ethanol/cyclohexane(solution A) and cyclohexane (solution B) on a hydrophilic substrate.We found that the droplet size increases first and then decreaseswith an increase of the initial ethanol concentration in solutionA. This is attributed to the phase separation of ethanol–cyclohexane–water;in particular, the composition of solution A on the phase boundaryabove the Ouzo region. The same reason also contributes to the lowerefficiency in droplet formation for a longer alkane. The importantimplication from this work is that the maximal droplet volume is limitedby the phase separation of the solvents used in the solvent exchange. [ABSTRACT FROM AUTHOR]