Layer-by-layer (LbL) assembly is a convenient and versatile surface functionalization method. However, the preparation of a thick film via LbL assembly is a challenging endeavor, as well as laborintensive and time-consuming. In this study, we introduce a phenomenon called Self-Enhancement in the thickness of an LbL Film (SELF). We revealed that methyl-π interactions between the chemically tethered catechol (aromatic ring, π) and the acetyl (-CH3) groups in a chitosan backbone occur in the SELF phenomenon. A thick free-standing film produced by SELF was shown to function as a high-capacity protein reservoir.