Methods are provided for controlled reservoir opening, including the steps of (a) providing a biocompatible implantable device which comprises at least one substrate, a plurality of reservoirs in the substrate, reservoir caps each of which covers one of the reservoirs, and molecules sealed inside the reservoirs; and (b) selectively heating each reservoir cap in an amount effective to rupture the reservoir cap and open the reservoir. In another embodiment, the method steps include (a) implanting into a patient a biocompatible device which comprises at least one substrate, a plurality of reservoirs in the substrate, reservoir caps each of which covers one of the reservoirs, and molecules sealed inside the reservoirs; and (b) selectively heating each reservoir cap in an amount effective to rupture the reservoir cap and open the reservoir.