A METHOD FOR PRODUCING AN ARRAY OF PORES OF CYLINDRICAL SHAPE IN A POLYMER FILM, AND A POLYMER FILM PRODUCED ACCORDING TO THE METHOD

摘要

A method for producing elongated cylindrical micro-pores (2) in a polymer film (1) comprises drop-casting a thin film (22) of a low polymer concentration solvent solution comprising approximately 3.5% by mass polymer and 96.5% by mass solvent on a planar horizontal upwardly facing surface (20) of a substrate (18) in an elongated chamber (17). A first gas flow of nitrogen gas of relative humidity of 2% to 5% is passed through the chamber (17) over a gas/film interface surface (55) of the film solution (22) for approximately 45 seconds to initially accelerate solvent evaporation from the film solution (22) in order to establish a polymer concentration gradient which extends into the film solution (22) from the gas/film interface surface (55) with the polymer concentration highest at the gas/film interface surface (55). A second gas flow of nitrogen gas of relative humidity of approximately 85% is then passed over the gas/film interface surface (55) until all the solvent has been evaporated. Water condensing on the gas/film interface surface (55) from the second humid gas flow forms water droplets, which grow and sink into the film solution (22). The second gas flow controls the downward rate of growth of the polymer concentration gradient into the film solution (22) so that it is matched with the downward rate of growth of the water droplets. This stabilises the water droplets, thereby resulting in the formation of the cylindrical pores (2).