The present invention concerns the use of a semipermeable hollow fiber membrane having the selective layer on the outer wall surface in hemodialysis, as a sensor membrane for direct blood contact, as a sensor membrane in water applications, such as waste water applications, and delivery membrane in biological processes. The membrane has the smallest pore size on the outer wall surface, and has an outer wall surface which is smooth, continuous and homogeneous on a nanoscopic scale. Further the present invention concerns devices comprising the semipermeable hollow fiber membrane.
