Phase change thermal-sink apparatus

A thermal sink cooling cartridge, comprising:

• a base container having a bottom surface, an opening, and exterior side walls extending between the bottom surface and the opening and tapering outwardly from the bottom surface to the opening, said bottom surface and exterior side walls forming an outermost exterior surface of the fully-assembled thermal sink cooling cartridge, said bottom surface further comprising an expansion panel configured to expand in response to an increased pressure within the base container to maintain overall exterior dimensions of the thermal sink cooling cartridge in use;
• a thermoconductive cover having an undersurface coupled to and enclosing the opening of the base container and adapted to provide a thermally conductive interface between the thermal sink cooling cartridge and an external object placed on the thermoconductive cover in direct contact and to be maintained at a desired cooled temperature;
• a fluid tight seal interposed between the opening and the thermoconductive cover;
• and
• a phase change material comprising an aqueous material having a liquid phase and a solid phase, the solid phase being buoyant within the liquid phase, said phase change material entirely filling the base container in both the liquid and solid phases such that the phase change material is in continuous contact with the undersurface of the thermoconductive cover, wherein solidification of the aqueous medium induces the increased pressure within the base container.