A new method has been developed to fabricate multilayer films by superimposing free-standing films and the resulting film was utilized as the barrier coating to control the drug release. First, the poly(lactic acid) (PLA) free-standing film was prepared by using polyvinyl alcohol (PVA) as a sacrificial layer. Then the PLA film was transferred or layer-by- layer overlaid on the drug-loaded film. Finally, the drug release process of the as-covered drug-loaded film was investigated. The prepared PLA free-standing film was smooth and robust, and the thickness increased linearly with the solution concentration. It is worth mentioning that on the bottom surface of the PLA film there was the PVA residue from the sacrificial layer, which can't be completely removed. That may facilitate the fabrication of the multilayer by superimposing because the PVA could provide interaction between the layers through hydrogen bonding. The free-standing films with about 50, 100 and 200 nm thickness were transferred and overlaid. The SEM observation shown that the transferred film could fully cover the target surface and the morphology was basically smooth. The thickness of the multilayer film was in agreement with the expected value. All of these indicated that the multilayer fabrication was successful. The multilayer PLA films can efficiently control the drug release. Moreover, the transferred film was more efficient than the in-situ spin film and the multilayer film was more efficient than the monolayer film. This may be attributed to the gap between the transferred free-standing films, which holds the released drug, retarding the release rate. The concept to fabricate the multilayer by superimposing free-standing film provides a new approach to control drug release and has great potential in the biological materials and medical implant devices.

Key words: layer-by-layer assembly, poly(lactic acid), free-standing film, blocking layer, controlled release