A nanoscale thermal switch can be built by employing nanoscale effects that arise when heat is transferred between a hot and cold nanoscale-thick membrane via thermal radiation. In comparison to the vast array of devices, such as transistors and diodes that are available to control the flow of electricity, there exist very few proposals for controlling the flow of heat, especially at the nanoscale. To overcome this challenge, researchers have been exploring nanoscale phenomena that may enable novel functional thermal devices.
The researchers created the thermal switch by controlling the emission properties of the nanomembranes by bringing a third object into close proximity of the nanomembrane. In order to test the technology, the team developed a scheme where a planar object can be brought into close proximity (microns) of two co-planar membranes that were exchanging heat. Both suspended calorimetric devices that had unprecedented calorimetric resolution and a planar mesa-shaped object were nanofabricated and the separation between them was controlled using a custom nanopositioner. From these experiments, the researchers could show that heat transfer between nanoscale membranes can be turned on and off by simply modifying the separation between the membranes and the planar mesa.
In order to make precise numerical predictions of the experimental observations, the researchers performed detailed calculations that showed how the observations can be quantitatively related to how the propagation of light, which is the carrier of heat, from one membrane to the other is impeded by the planar mesa, which can either absorb the light propagating between the membranes or reflect it away from the membranes.