We find that acoustoinjection of droplets take place for fluorosurfactant concentrations of 1, 3 and 5 wt% (Fig. ). The most efficient and reproducible injection occurs with 3 wt% fluorosurfactant concentration (Fig. pink squares and an example for acoustic pressure fieldmediated injection in Video S3), displaying a balance between interfacial tension and impact of the acoustic field on destabilizing the surfactant layer to permit droplet injection. At 1 wt% fluorosurfactant concentration (Fig. blue circles), some droplets after injection also coalesce with each other as an effect of the higher interfacial tension and the associated lower stability of the water-in-oil droplet. With increasing surfactant concentrations (Fig. green triangles), the droplet stability increases and the average change in the droplet aspect ratio, taken as the length of the droplet in the channel by the width of the channel, decreases. Moreover, it seems