A technique of manufacturing an elastomeric container closure or plunger with embedded functional components to avoid thermal damage to the components is described. The technique includes molding a drug-contacting part from a first material at a first temperature and for a first length of time defining a first thermal exposure; after molding the drug-contacting part, inserting ancillary components into the drug-contacting part, where the ancillary components have an operational thermal budget less than the first thermal exposure; and overmolding the drug-contracting part and the ancillary components with a second material at a second temperature for a second length of time to form a non-drug-contacting part that mechanically connects the non-drug-contacting part and the drug-contacting part to form the elastomeric container closure and seals the ancillary components inside the elastomeric container closure. The overmolding defines a thermal exposure less than the operational thermal budget of the ancillary components.