Reservoir-based devices are provided in which an individual reservoir has at least two openings with a support structure therebetween and closed by reservoir caps covering the openings to control release or exposure of reservoir contents. In one embodiment, the device is an implantable medical device and provides for the controlled release of drug or exposure of a sensor. The device includes a substrate; at least one reservoir disposed in the substrate, the reservoir having two or more openings; reservoir contents located in the reservoir; two or more discrete reservoir caps, each reservoir cap sealingly covering at least one of the reservoir openings; and control means for selectively disintegrating or permeabilizing the reservoir caps.