The present disclosure concerns a membrane for a sensor, such as an opto-chemical or electrochemical sensor, including a polymer layer, for example, one featuring pores or openings, that is permeable to a measuring fluid and/or an analyte contained in the measuring fluid, with a surface designed to be in contact with a measuring fluid, wherein the surface is designed such that, at least in a moist condition of the polymer layer obtained by moistening the surface, a contact angle of a water drop applied to the surface is less than 50°, including less than 30°, and including less than 10°.