A heat sink uses thermally conductive ferrofluid to cool an integrated circuit. A direction of flow of the ferrofluid in the heat sink is controlled by a motorized pump assembly. The motorized pump assembly uses a motor to rotate a metal plate to which at least one magnet is connected. The direction of flow of the ferrofluid is dependent on a magnetic field induced between the at least one magnet and at least one magnetic particle in the ferrofluid passing through the motorized pump assembly.