Fig. 5. Performance as both a thermal regulator and a thermal switch.
a Device temperature as a function of ambient temperature at each thickness of graphene foam, for a constant heat flux. The temperature difference between device and environment at the uncompressed and fully compressed states are 17.4 °C and 7.0 °C, respectively, resulting in a switching ratio of ~2.5. The temperature window over which the device temperature can be controlled is ~10 °C from the minimum to maximum Td at each ambient temperature level at this heat flux (the range illustrated by the blue dashed line) and can be extended to 20.4 °C (the range between the brown and the blue dashed lines) when the operating temperature is a range from 20 °C to 30 °C (displayed by the blue shade). b Contour plot showing the capacity of graphene foam for continuous temperature regulation with varying ambient temperatures. To achieve a constant device temperature, the thickness of the graphene foam, dgf, should be adjusted following one of the isotherms as the ambient temperature is varied. c Device temperature as a function of the heat flux at different thicknesses of the graphene foam. d Contour plot showing the capacity of graphene foam for continuous regulation based on heat load. To maintain a particular device temperature above the ambient temperature, the thickness of the graphene foam can be controlled following the isotherms as the input heat flux is varied.