A new technique has been developed that now makes it possible to manipulate heat as if it were light, controlling it in the same ways that you can control light waves. This technique could have a lot of very interesting uses in thermoelectric devices and for developing energy efficiency systems in buildings.
The technique is based on “engineered materials consisting of nanostructured semiconductor alloy crystals,” the Massachusetts Institute of Technology (MIT) writes. “Heat is a vibration of matter — technically, a vibration of the atomic lattice of a material — just as sound is. Such vibrations can also be thought of as a stream of phonons — a kind of ‘virtual particle’ that is analogous to the photons that carry light. The new approach is similar to the recently developed photonic crystals that can control the passage of light, and phononic crystals that can do the same for sound.”
By controlling the spacing of tiny gaps that are present in these materials, it’s possible to tune them to match up with the wavelength of the heat phonons.
“It’s a completely new way to manipulate heat,” Martin Maldovan, research scientist in MIT’s Department of Materials Science and Engineering says. “Heat differs from sound, he explains, in the frequency of its vibrations: Sound waves consist of lower frequencies (up to the kilohertz range, or thousands of vibrations per second), while heat arises from higher frequencies (in the terahertz range, or trillions of vibrations per second).”
The overall process (while more complex than this), is essentially to ‘reduce’ the heat phonons until they are more similar to sound waves, and then manipulate the narrowed beam of “hypersonic heat” that results, by using phononic crystals like the ones used to control sound phonons. These are being referred to as “thermocrystals” by the researchers.
The researchers think that these thermocrystals could be used very effectively for a wide variety of interesting purposes. Among these possibilities are: better thermoelectric devices, “one-way heat flows” that would be very useful for energy efficiency, and “thermal cloaking”, which has a wide-variety of potential uses.
The new findings were just published January 11th in the journal Physical Review Letters.