Microchip delivery devices are provided that control both the rate and time of release of molecules, wherein the device includes a substrate, at least one reservoir in the substrate containing the molecules, and a reservoir cap positioned on the reservoir over the molecules, wherein the molecules are released from the reservoir upon heating or cooling the device or a portion thereof sufficient to rupture the reservoir cap. In a preferred embodiment, the device includes a resistor integrated into the reservoir or mounted near the reservoir, which upon application of an electric current through the resistor, causes at least one of the contents of the reservoir to thermally expand, vaporize, phase change, or undergo a thermally driven reaction, such that the reservoir cap ruptures due to mechanical stress. In another preferred embodiment, application of an electric current to a resistor located on or near the reservoir cap causes the cap to expand, contract, or undergo a phase change that results in the rupture of the reservoir cap. The reservoirs can contain multiple drugs or other molecules in variable dosages. Each of the reservoirs of a single microchip can contain different molecules and/or different amounts and concentrations, which can be released independently.