polymer filter film for which pores are etched along beam tracks only in a first , porous region , and which has a second , impermeable region , in particular in the form of a peripheral region . the peripheral region is made etch - resistant by a heat treatment of the beam tracks . advantageous embodiments of the method are used to produce microchambers in the film for holding a cell culture . they can advantageously be used for enzymatic sensors and microbiological reactors .