The U.S. Department of Defense has awarded a $6.25 million grant to University of Michigan researchers and their partners to study heat transfer at the nanoscale for applications such as converting heat to electricity and an optical approach to cooling electronic devices.
Pramod Reddy and Edgar Meyhofer, U-M professors of mechanical engineering, have previously worked on understanding energy flow at the nanoscale and its application in converting heat to electricity via a novel photovoltaic approach. They’ve also demonstrated that light emitting diodes (LEDs) can be made to cool devices that sit mere nanometers away.
In partnership with four other universities, U-M’s team will lead research to further work in both areas.
“Understanding the principles of energy conversion and photon transport at the nanoscale, which are very different from classical laws that describe macroscale phenomena, is critical for developing novel technologies for energy conversion and information processing,” Reddy said.
The new grant, awarded by the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory, through its Army Research Office is part of DOD’s Multidisciplinary University Research Initiative (MURI). The program promotes research by teams of investigators that intersect more than one traditional science and engineering discipline. The base grant is for three years, with the possibility of a two-year extension.
In 2016, Reddy and Meyhofer’s research team demonstrated a new approach to thermal radiation that offered a challenge to the 120-year-old theory of radiation, first proposed by Max Planck. They showed in a series of papers from 2016 to 2018 that energy transfer rates can be up to 1000 times faster than Planck’s predictions for objects separated by nanoscale gaps.
Thermal radiation is the transfer of heat via light, in the form of photons, between hot and cold objects. When the gap size is reduced to the nanoscale, objects are said to be in the near-field of each other, and the past theories of radiative heat transfer are not applicable.
Elucidating the principles of near-field heat transfer could enable a number of future nanotechnologies for energy conversion.
“Insights from this work are expected to enable efficient heat-to-electric energy conversion devices and novel solid-state refrigeration devices that rival current technologies,” Meyhofer said.
Earlier this year, Meyhofer and Reddy demonstrated that an LED, with its polarity reversed, could cool a nearby device. Next to laser cooling, it is the only method devised to use photons as a means to cool and may offer a pathway to efficient cooling rivaling, for example, peltier-based approaches.
The approach could lead to new solid-state cooling technology for future microprocessors, which will have so many transistors packed into a small space that current methods can’t remove heat quickly enough.
U.S. Army officials have previously described Reddy and Meyhofer’s previous work as “breakthrough research.”
“Advancements in near-field thermo-photovoltaics (TPV) will enable soldiers to harness high-efficiency power from any heat source on the battlefield,” said Dr. Pani Varanasi, chief of the Materials Science Division of the Army Research Office, an element of CCDC ARL. “This research may also spur the development of near-field-based thermal diodes and thermal transistors that could enable innovative thermal-based computing for niche future applications as well as in thermal management of high-power electronics.”
Institutions contributing to the project include Massachusetts Institute of Technology, Purdue University, Stanford University and Yale University.