A heat sink uses a ferrofluid-based pump assembly for controlling the direction of nanofluid flow within the heat sink. The nanofluid is thermally conductive and absorbs heat from a heat source, which is then directed away from the heat source by the ferrofluid-based pump assembly. The ferrofluid-based pump assembly uses a motor to rotate at least one magnet so as to rotate ferrofluid contained in the ferrofluid-based pump assembly. The direction of nanofluid flow within the heat sink is dependent on the movement of ferrofluid in the ferrofluid-based pump assembly.