Pop Research Group explores Control of Heat Transfer at the Nanoscale

November 2018

Researchers from the Pop Lab, with help from UC Davis researchers, published an article about electrochemically-driven nanoscale thermal regulators.

The paper's abstract states, "the ability to actively regulate heat flow at the nanoscale could be a game changer for applications in thermal management and energy harvesting. Such a breakthrough could also enable the control of heat flow using thermal circuits, in a manner analogous to electronic circuits. Here we demonstrate switchable thermal transistors with an order of magnitude thermal on/off ratio, based on reversible electrochemical lithium intercalation in MoS2 thin films."

In order to make this heat-conducting semiconductor into a transistor-like switch, the researchers bathed the material in a liquid with lots of lithium ions. When a small electrical current is applied to the system, the lithium atoms begin to infuse into the layers of the crystal, changing its heat-conducting characteristics. As the lithium concentration increases, the thermal transistor switches off. Working with Davide Donadio's group at the University of California, Davis, the researchers discovered that this happens because the lithium ions push apart the atoms of the crystal. This makes it harder for the heat to get through.

The researchers envision that thermal transistors connected to computer chips would switch on and off to help limit the heat damage in sensitive electronic devices.

Besides enabling dynamic heat control, the team's results provide new insights into what causes lithium ion batteries to fail. As the porous materials in a battery are infused with lithium, they impede the flow of heat and can cause temperatures to shoot up. Thinking about this process is crucial to designing safer batteries.

In a more distant future the researchers imagine that thermal transistors could be arranged in circuits to compute using heat logic, much as semiconductor transistors compute using electricity. But while excited by the potential to control heat at the nanoscale, the researchers say this technology is comparable to where the first electronic transistors were some 70 years ago, when even the inventors couldn't fully envision what they had made possible.

Excerpted from "How can we design electronic devices that don't overheat?" Nov 9, 2018.

 

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