Abstract: The invention disclosed herein relates to a heat sink or heat exchanger derived from a planar silicon substrate (e.g., a silicon wafer). In some embodiments, a cooling fluid (gas or liquid) is flowing through the plurality of flow-through pores that extend through the planar silicon substrate. In still further embodiments, the present invention is directed to methods of using a porous silicon substrate as a heat sink or heat exchanger to dissipate and/or transfer heat away from a device such as, for example, a microprocessor associated with a computer system. In this regard, the inventive method comprises at least the following steps: allowing heat to dissipate away from the heated component and into the porous silicon substrate; and passing a first cooling fluid through the plurality of flow-through pores of the porous silicon substrate such that heat is transferred away from the porous silicon substrate and into the first cooling fluid.