Schematic illustration of the fabrication of free-standing (a) and supported (b, c, d) films. Teflon substrate was used to construct free-standing film and PET substrate was used for the supported films. First, the substrates were alternately immersed in PEI-Ag+ (pH=9.0) and PAA (pH=3.2) solutions to form 20 (a, b, c) or 19.5 (d) bilayered films (PAA-ending films or PEI-Ag+-ending films). Then, the films were heated in a sealed chamber to be thermally cross-linked (CL) in the presence (a, b, d) or absence (c) of an additional silane coating. Finally, free-standing film with top surface superhydrophobic and bottom surface hydrophilic (a) was obtained from Teflon substrate, and supported superhydrophobic film (b), supported rough hydrophobic film (c) and flat supported hydrophobic film (d) were obtained on PET substrate.