Lysozyme fibrils were prepared by dissolving 2% (w/v) lysozyme monomers (from hen egg white) in a strong acidic solution (206 mM HCl and 200 mM NaCl), followed by vigorous stirring at a shear rate of 8 rad s -1 at 70 ℃. After incubation for 65 hours, the resulting fibrils have dimensions of 500-1000 nm in length, and 15-20 nm in thickness. After suspended in a mixture of 7% PEG and 3% dextran, the fibrils (0.05-0.2 wt%) can be adsorbed at the W/W interface and stabilize W/W emulsion droplets at pH= 2-4. When the medium pH is adjusted to 7, the β-sheet structure of lysozyme fibrils become unstable, and they partition into the dextran-rich droplet phase (Fig. ). According to the Bancroft's rule, an effective surfactant of emulsion should have a higher affinity in the continuous phase than the droplet phase, we thus grafted polyethylene glycol (PEG) to the lysozyme fibrils and enhances their affinity to the PEG-rich continuous phase. Experimentally, lysozyme fibrils were first decorated with furan moieties, and the furan modified fibrils were further reacted with maleimidedecorated multi-arm-PEG (Mw: 10 kDa) through Diels-Alder (D-A) click chemistry (see schematic Fig. ). According to the FT-IR spectrum in Fig. , (MAL)4-PEG exhibits characteristic absorption peak at 695 cm -1 and 1468 cm -1 , which correspond to the bending motion of ═C-H and C═C bonds in the maleimide. After the fibrils are modified with (MAL)4-PEG, an absorption peak appears at 1771 cm -1 , in accordance with C═C stretching vibrations of the D-A adduct. The results confirm the successful connection of multi-arm PEG with fibrils. By varying the mass ratios of multi-arm PEG to lysozyme fibrils (see Table ) in the reaction mixture, we obtain a serial of PEGylated fibril clusters with increasing PEG fractions from 49 wt% to 86 wt.%, named as sample PF-1, PF-2, PF-3, PF-4 (see specific compositions in table ). As the PEG fraction in the fibril cluster increases, the hydrodynamic diameter of the PEGylated fibril clusters increases from 1 micrometer to 10 micrometers, as evidenced by both dynamic light scattering (DLS) measurement (Fig. ) and scanning electron microscopy (SEM) observation. Due to the shielding of charge induced by 4-arm PEG moiety, the zeta potential of fibril decreases from +27 mV to +11 mV (Fig. ). SEM observation reveals the number of fibrils in each cluster typically varies from 6 to 40 pieces, Fig. ).