Heat can cross a tiny vacuum gap far more efficiently than ordinary thermal radiation would suggest. Researchers have now shown that carefully patterned metamaterials can amplify this nanoscale energy flow by as much as four times, offering experimental evidence that heat transfer can be engineered rather than simply managed.
The study, published in Nature by researchers at Carnegie Mellon University, Stanford University, and Purdue University, focuses on near-field radiative heat transfer. This effect appears when two objects are separated by only a few hundred nanometers, allowing electromagnetic interactions that are negligible at larger distances to dominate the exchange of thermal energy.
At everyday distances, objects primarily exchange heat through familiar processes such as conduction, convection, and thermal radiation. But when surfaces move extremely close together, electromagnetic fields associated with one surface can interact directly with the other. Energy can then cross the gap through near-field effects, producing heat transfer rates that greatly exceed what conventional far-field radiation would allow.
Scientists have studied this phenomenon for years, but the new work demonstrates experimentally that artificial structures can strengthen it even further. The researchers patterned microscopic gold structures onto thin membranes, then positioned two patterned surfaces face to face across a nanoscale gap.
“Unlike conventional materials, metamaterials are built with tiny, repeating patterns that interact with energy in precise ways,” said Sheng Shen, a professor of mechanical engineering at Carnegie Mellon University and senior author of the study. “We patterned microscopic gold structures onto thin membranes and positioned them face-to-face across a nanoscale gap. This increased heat transfer by as much as four times compared to similar setups without metamaterials, which is far beyond what traditional physics would predict at larger distances.”
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