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Heat Flow Controlled With Atomic Precision by Illinois Scientists

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Heat flow can now be controlled with atom-level precision. This, as has been demonstrated by investigators from the University of Illinois, can be achieved through a combination of a design of atomic-scale materials and ultrafast measurements to regulate how heat flows between two materials across an interface.  In a study published this week in Nature Materials, the researchers showed that a single layer of atoms can enhance or disrupt heat flow across a specific interface.

Enhanced performance in modern technologies very much depends on improved heat exchange regulation in combustion engines and integrated circuits. Other emerging technologies like thermoelectric devices that are used in harvesting renewable energy from waste heat also depend on precise heat control mechanisms.

But this is usually hampered by the incomplete understanding of heat conduction between materials. A Willet Professor and Head of Materials Science and Engineering at the University of Illinois, David Cahill, stated that heat travels via ‘phonons’ in electrically insulating material. Commenting about phonons, the professor said that they are “collective vibrations of atoms that travel like waves through a material.”

Over the past decade, Cahill and his team have developed a measurement technique using extremely short laser pulses lasting only a trillionth of a second. This was done so as to probe and accurately decipher heat flow at atomic scale with nanometer-depth resolution. The team has also in collaborated with Paul Braun, also a professor in the same department and a leader in the nanoscale synthesis of materials.

The analysis of heat transfer in an atomic level was done by preparing what the researchers called a molecular layer sandwich on a quartz surface. After this, they used a transfer-printing technique using a very thin gold film on top of the molecular layer and applying a heat pulse.

This heat pulse was then measured when different molecules were in contact with the gold layer. They analyzed the changes in heat transfer against different bonding strengths and found out that the stronger the bonding, the higher the increase in heat flow.

Mark Losego, one of the team leaders and postdoctoral scholar at the University of Illinois said, “Changing even a single layer of atoms at the interface between two materials significantly impacts heta flow across that interface.”  The work was supported by the Air Force office of Scientific Research.

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