Fabrication of planar and curved polyimide membranes with a pattern transfer method using ZnO nanowire arrays as templates

Nanoporous polymer membranes have been fabricated for various biomedical applications, including biosorting and drug delivery, as well as for water purification. However, the preparation of curved nanoporous polymer membranes has rarely been reported. In this paper, we report a facile and reliable method for fabricating both planar and curved polyimide membranes with nanopores by employing ZnO nanowire arrays as templates. First, we prepared ZnO nanowire arrays with lengths ranging from 2 to 10 mu m on both flat and curved glass substrates via a hydrothermal method; their length was controlled by the reaction time. The number density of the nanowires could be adjusted by changing the concentration of the ZnO seed solution. Second, liquid polyimide was applied to the ZnO nanowire arrays, which was then cured at 200 degree C. Finally, the nanoporous polyimide membranes were formed by etching the ZnO nanotemplates and glass substrates. The shape and size of the nanopores formed in the polyimide membranes closely matched that of the nanowire templates.