The invention relates to a delivery device suitable for delivering a chemical substance, e.g. a medical device such as a catheter, a microcapsule, an implantable capsule or a P-ring, or a delivery device for use in the construction industries e.g. in the form of microcapsules comprising antifouling agent for marine paint. The delivery device comprises a closed cavity, the cavity is defined by an innermost wall surface, wherein at least a section of the inner wall surface constitutes an inner surface of a delivery membrane wherein the delivery membrane comprises an interpenetrating polymer network substrate comprising a host polymer and a guest polymer, where the guest polymer is interpenetrating the host polymer to form substantially continuous pathways within said host polymer.