Physicists design material that conducts one way and insulates the other.
Stiffness and springiness could make heat stop and go.
European physicists have sketched out a blueprint for a valve that lets heat pass only one way. The proposed material conducts heat flowing in one direction, but also behaves as an insulator, stopping it going the other way1.
In theory, a heat valve could keep parts of microelectronic circuitry cool or channel heat to chip-sized chemical reactors, which are currently being developed for high-efficiency chemical synthesis or ultra-sensitive analysis.
Heat corresponds to the movement of atoms. When atoms are joined together in molecules, they vibrate back and forth. The larger the vibrations, the hotter the material.
Heat is conducted along a chain of particles because vibrations travel from one particle to the next. If one end is attached to a hot material and the other to something cooler, the hot end jiggles more. This jiggling goes down the chain to the cool end.
A chain of particles of identical weights linked by ideal, so-called harmonic springs vibrates at the same frequency irrespective of the amplitude of the vibrations. In real chains, like DNA, the links are not ideal, but anharmonic: their vibration frequency depends on amplitude.
One-way heat transfer would make use of anharmonicity. A chain divided into three sections, say Terraneos team, can insulate heat if the middle section acts like a strongly anharmonic spring while the outer two are softer and more harmonic.
If one of the end sections is stiffer than the other, more heat can flow in one direction than the other. The anharmonic middle of the chain can jiggle in sympathy with the stiff end when it is cold and the soft end when it is hot - but not vice versa. So the chain transmits heat from a hot, soft end to a cool stiff end. If the stiff end gets hot and the soft cold, the middle section blocks vibrations, so the chain as a whole acts as an insulator.
PHILIP BALL | © Nature News Service
Tiny lasers from a gallery of whispers
20.09.2017 | American Institute of Physics
New quantum phenomena in graphene superlattices
19.09.2017 | Graphene Flagship
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
20.09.2017 | Life Sciences
20.09.2017 | Power and Electrical Engineering
20.09.2017 | Physics and Astronomy