Next, we investigated the interfacial stability of W/W emulsions after addition of PEGylated fibril clusters (Fig. ). Fibril clusters with different PEG fractions were synthesized and stained by thioflavin T and suspended in an emulsion mixture of 3% dextran / 7% PEG / 90% H2O at the concentration of 0.05%-0.15% (w/v, counted by protein fibrils). After vortex mixing, the fibril cluster-stabilized emulsion droplets were observed using fluorescence microscopy. With an increasing PEG fraction in the fibril cluster, more fibrils were observed to translocate from the dextran-rich droplet phase to the W/W interface, resulting in a higher density of stable W/W droplets with decreasing droplet size (Fig. and). The observation suggests that the 4-arm PEG enhances the partitioning affinity of fibril cluster to the continuous phase and W/W interface, thereby improves the emulsion stability. By fixing the PEG fraction (at PF-4) and increasing the concentration of fibril cluster, the average diameter of the W/W emulsion also decreases, suggesting that the stabilized total interfacial area of the emulsion mixture increases with the concentration of fibril cluster. (Fig. ).