Thermal conductivity control devices

A system (100; 200) for controlling thermal conductivity between two thermal masses (102, 104; 202, 204) is disclosed. The system includes a first conduction body (110; 210) in thermal contact with a heat source (102; 202) and a second conduction body (120; 220) in contact with a heat sink (104; 204). A thermal expansion component (140; 240) operatively connects to the first conduction body and moves the body between first and second positions at a predetermined temperature. In the first position the first conduction body is spaced apart from the second conduction body, thermally isolating the heat source from the heat sink. In the second position the first conduction body thermally contacts the second conduction body, and conducts heat from the heat source, through the conduction bodies and into the heat sink. Related methods are also described.