Thermal Transistors...

TECHNOLOGY REVIEW: In recent years, engineers have begun to design and test thermal transistors with some success. Their goal is to exercise the same control over heat that they already have over electric current–the ability to switch it on and off, to modulate it and even to amplify it.

That would be hugely useful for managing heat dissipation but also for creating thermal logic gates that can process information in the form of heat.

The thermal transistors built so far all work by modulating the flow of phonons, or thermal vibrations, from one material to another. For this to work, materials must be in physical contact with one another.

But there is another way for heat to flow–by radiative transfer. In this case, heat flows with the passage of thermal photons from one material to another. In this case, the materials do not need to be in physical contact.

Today, Philippe Ben-Abdallah at the Université Paris-Sud in France and Svend-Age Biehs at Carl von Ossietzky Universität in Germany, unveil the first thermal transistor to operate on thermal photons. The big advantage of this device is that it works at much higher speed than phonon transistors, potentially at light speed.

The design is simple. The transistor consists of three parts, which Ben-Abdallah and Biehs call the source, drain and gate, in analogy to a conventional transistor. The source and drain are made of silica and held at different temperatures to create a temperature gradient.

The source, which is hotter than the drain, emits thermal photons which transfer heat to the drain.

Physics arXiv: Near-field thermal transistor