4. ConclusionsOur results show that the formation and stability of Janus emul-sion droplets in the ternary olive oil/water/silicone oil systemstrongly depends on the interfacial tension at the oil/water inter-face. By using Tween 80, i.e. a biocompatible non-ionic surfactant,the interfacial tension between olive oil and water is decreasedto 3 mN/m and completely engulfed Janus droplets are formed.When the viscosity of both oil components is of the same order(OO and SiO2) significantly larger droplets are formed. The dropletsize can be decreased by lowering the viscosity of the silicone oilor by adding phospholipids. In presence of phosphatidylcholinethe interfacial tension is decreased to 0.5 mN/m, and more sta-ble Janus droplets are formed. Briefly examine the evidence onecan assume that the phosphatidylcholine, embedded in the inter-facial film between olive oil and water, stabilize the droplets againstcoalescence due to an additional electrostatic effect of the ampho-teric head groups. The synergistic effect in presence of Tween 80can be understood by the formation of a mixed film layer containingpolyethylenglycol sorbitan monooleate and phosphatidylcholine.Based on similar ring tensiometer experiments Hameed et al. [25]concluded that Tween molecules are not tightly packed on theinterface between olive oil and water, but might be in a tilted state.Therefore, one can assume in our case a more ordered structurein presence of phosphatidylcholine. Nevertheless, additional mea-surements are needed to characterize the orientation of the mixedsurfactant film.