A thermal sink cooling cartridge, comprising: an expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) having a bottom surface, an opening, and flared side walls tapered outwardly from the bottom surface to the opening; a thermoconductive cover (105, 205, 305, 505, 640, 705, 1060, 1115) having an undersurface coupled to and enclosing the opening of the expandable base container (110, 220, 310, 510, 620, 710, 1030, 1110) and adapted to provide a thermally conductive interface between the thermal sink cooling cartridge and an external object placed on the thermoconductive cover (105, 205, 305, 505, 640 705, 1060, 1115) in direct contact and to be maintained at a desired cooled temperature; a fluid tight seal interposed between the opening and the thermoconductive cover (105, 205, 305, 505, 640, 705, 1060, 1115); and a phase change material entirely filling the expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) and having in use a solid phase (230, 325) and a liquid phase, characterized in that the phase change material is an aqueous medium wherein the solid phase is buoyant within the liquid phase, and in that: - the bottom surface includes at least one expansion panel wherein the interior volume of the expandable base container (110, 220, 315, 510, 620, 710, 1033, 1110) expands in response to increased pressure within the expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) in use due to the changing of phase of the aqueous medium, and adapted for maintaining the overall exterior dimensions of the thermal sink cooling cartridge following the expansion of the aqueous medium; or - the thermal sink cooling cartridge comprises a compressible element that is provided in contact with the aqueous medium and comprising a volume which reduces in response to external pressures exerted by the aqueous medium in use due to the changing of phase of the aqueous medium, and wherein the expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) is adapted such that a solid phase portion of the phase change material is in contact with the undersurface of the thermoconductive cover (105, 205, 305, 505, 640, 705, 1060, 1115). an expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) having a bottom surface, an opening, and flared side walls tapered outwardly from the bottom surface to the opening; a thermoconductive cover (105, 205, 305, 505, 640, 705, 1060, 1115) having an undersurface coupled to and enclosing the opening of the expandable base container (110, 220, 310, 510, 620, 710, 1030, 1110) and adapted to provide a thermally conductive interface between the thermal sink cooling cartridge and an external object placed on the thermoconductive cover (105, 205, 305, 505, 640 705, 1060, 1115) in direct contact and to be maintained at a desired cooled temperature; a fluid tight seal interposed between the opening and the thermoconductive cover (105, 205, 305, 505, 640, 705, 1060, 1115); and a phase change material entirely filling the expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) and having in use a solid phase (230, 325) and a liquid phase, characterized in that the phase change material is an aqueous medium wherein the solid phase is buoyant within the liquid phase, and in that: - the bottom surface includes at least one expansion panel wherein the interior volume of the expandable base container (110, 220, 315, 510, 620, 710, 1033, 1110) expands in response to increased pressure within the expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) in use due to the changing of phase of the aqueous medium, and adapted for maintaining the overall exterior dimensions of the thermal sink cooling cartridge following the expansion of the aqueous medium; or - the thermal sink cooling cartridge comprises a compressible element that is provided in contact with the aqueous medium and comprising a volume which reduces in response to external pressures exerted by the aqueous medium in use due to the changing of phase of the aqueous medium, and wherein the expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) is adapted such that a solid phase portion of the phase change material is in contact with the undersurface of the thermoconductive cover (105, 205, 305, 505, 640, 705, 1060, 1115). - the bottom surface includes at least one expansion panel wherein the interior volume of the expandable base container (110, 220, 315, 510, 620, 710, 1033, 1110) expands in response to increased pressure within the expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) in use due to the changing of phase of the aqueous medium, and adapted for maintaining the overall exterior dimensions of the thermal sink cooling cartridge following the expansion of the aqueous medium; or - the thermal sink cooling cartridge comprises a compressible element that is provided in contact with the aqueous medium and comprising a volume which reduces in response to external pressures exerted by the aqueous medium in use due to the changing of phase of the aqueous medium, and wherein the expandable base container (110, 220, 315, 510, 620, 710, 1030, 1110) is adapted such that a solid phase portion of the phase change material is in contact with the undersurface of the thermoconductive cover (105, 205, 305, 505, 640, 705, 1060, 1115).