Thermal Rectifiers Explained
In electronics we are fairly used to devices that allow an electrical current to flow in only one direction. Some years ago it was suggested that some materials could have a similar directional bias, but for thermal currents. Now researchers at Purdue University have finally explained this thermal rectification, and such knowledge could lead to some very interesting and useful technologies.
Similar to how electrical currents can be thought of as a flow of electrons, a thermal current can be thought of as a flow of phonons, the quanta of vibrational energy. What was suggested years ago was that asymmetrical graphene nanoribbons would act as thermal rectifiers, and have a bias for which direction the phonons travel. Now the researchers have explained that what enables this is lateral confinement of the phonons, which prevents the phonons from bouncing into each other. Graphene, being only an atom thick, is naturally able to confine the phonons properly, but now that we understand the mechanics, other thermal rectifiers could be developed as well, such as asymmetric nanowires, thin films, and even some quantum dots.
The most obvious use of thermal rectifiers is to control the direction heat can flow, potentially keeping a building from losing heat during winter. Such rectifiers could maybe also be developed into thermal transistors and logic gates too, which could have some interesting applications considering the amount of waste heat electronics generate.
Source: Purdue University