Abstract: An apparatus includes a heat sink configured to receive thermal energy from one or more heat sources. The heat sink includes a local reservoir configured to hold a liquid coolant, and the heat sink is configured to pass the thermal energy into the liquid coolant in the local reservoir in order to vaporize at least some of the liquid coolant. The apparatus also includes a membrane configured to allow vaporized coolant to pass through the membrane out of the local reservoir into an ambient environment and to prevent unvaporized coolant from passing through the membrane. The membrane is thereby configured to provide passive flow control for the liquid coolant. The membrane could include a vapor-permeable and liquid-repelling membrane. The membrane can also be configured to hold the liquid coolant in the local reservoir against one or more surfaces of the heat sink.

Abstract: A wedge-based heat switch includes a plurality of wedge segments on a shaft, an energy storage element (e.g., a spring or pressurized cavity) configured to store (and release) energy via compression or expansion of the element along the shaft and a temperature activated phase transition material. A temperature stimulus activates the phase transition material to release the stored energy and move the wedge segments axially along the shaft to expand or contract the plurality of wedge segments. The wedge-based heat switch may be configured as a unidirectional switch, either conductive-to-insulating or insulating-to-conductive, or a bi-directional switch. The specific design of the wedge-based heat switch is informed by such factors as unidirectional or bi-directional, required preloading of a surface, conductance ratio between conducting and insulating states, temperature stimulus, switching speed and form factor.

Abstract: An apparatus includes a heat sink configured to receive thermal energy from one or more heat sources. The heat sink includes a local reservoir configured to hold a liquid coolant, and the heat sink is configured to pass the thermal energy into the liquid coolant in the local reservoir in order to vaporize at least some of the liquid coolant. The apparatus also includes a membrane configured to allow vaporized coolant to pass through the membrane out of the local reservoir into an ambient environment and to prevent unvaporized coolant from passing through the membrane. The membrane is thereby configured to provide passive flow control for the liquid coolant. The membrane could include a vapor-permeable and liquid-repelling membrane. The membrane can also be configured to hold the liquid coolant in the local reservoir against one or more surfaces of the heat sink.

Abstract: A wedge-based heat switch includes a plurality of wedge segments on a shaft, an energy storage element (e.g., a spring or pressurized cavity) configured to store (and release) energy via compression or expansion of the element along the shaft and a temperature activated phase transition material. A temperature stimulus activates the phase transition material to release the stored energy and move the wedge segments axially along the shaft to expand or contract the plurality of wedge segments. The wedge-based heat switch may be configured as a unidirectional switch, either conductive-to-insulating or insulating-to-conductive, or a bi-directional switch. The specific design of the wedge-based heat switch is informed by such factors as unidirectional or bi-directional, required preloading of a surface, conductance ratio between conducting and insulating states, temperature stimulus, switching speed and form factor.