Improving the effective use and the recycling of waste heat in technology has long been a staple of engineering, but heat is a fickle mistress. Multiple principles that shift depending on the scale make manipulating heat vastly more difficult when approaching either very small or very large scales.
Engineers at the University of Minnesota (UoM) may be able to provide a key piece toward solving that puzzle by producing the first ever recording of heat moving through a material on the nano level.
In order to accomplish this feat, the engineering team made use of an FEI Tecnai Femto Ultrafast Electron Microscope capable of creating recordings in almost unimaginably fast “femtoseconds,” each of which is the equivalent of one millionth of one billionth of a second. It appears that every last femtosecond counts, however, as they observed the heat moving at a speed of 6 nanometers per picosecond, which is roughly the speed of sound.
The infinitesimal nature of the experiment meant that the utmost precision was required in provoking a heat response. To eliminate as many potential confounds as possible, the UoM crew used a brief laser pulse to rapidly heat a semiconductor material made up of a combination of tungsten diselenide and germanium.
Colorized image of the observation of nanoscale heat transfer. (Image courtesy of UoM College of Engineering.)
While the development of nanotechnologies has been going on for some time, no material is perfect. Without actual footage of how heat moves and responds to imperfections, it becomes very difficult to adjust future projects in order to reduce heat bleed.
The minute scale and time spans involved in making such observations was a major barrier until the decision to use an electron microscope.
While not introducing any new technology in and of itself, the discoveries made by the UoM engineers could help add precision to research such as that done by Columbia Engineering on improving heat transfer and provide a clearer medium for testing applied physics theories on the manipulation of heat using phonons, such as that proposed by Martin Maldovan.
David Flannigan, the lead researcher on the team, was quoted as saying that the team “was extremely excited” to observe such a sight, likening the observation to “a dream come true.” With the myriad potential applications this knowledge offers, there's plenty of reason for the rest of the engineering community to be excited, too!
For more information, visit the University of Minnesota.