For example, the microprocessors that power your smartphone and laptop are made up of billions of nanometer-sized transistors on a single chip. “It turns out that heat dissipation in these small transistor elements is a huge issue that is detrimental to the performance and reliability of these microprocessors,” says Mechanical Engineering Assistant Professor Dakotah Thompson.
Deeper knowledge of the energy conversion processes in those transistors could lead to new solutions for managing the heat dissipation.
But studying energy transport at the nanoscale requires new approaches and tools, because the classical laws of energy transport break down at very small length scales.
“Instead of relying on empirical laws that work at the macroscale, we need to understand the microscopic transport of the fundamental energy carriers themselves— electrons, photons, phonons and molecules,” says Thompson, who joined the mechanical engineering faculty in August 2019.
With this approach, Thompson’s goal is to gain a better understanding of thermal transport and energy conversion at nanometer-length scales. His research in this area could benefit many different industries and technologies.
One motivation for his research is to enhance alternative and renewable energy technologies, including solar photovoltaic and photocatalytic systems. For example, manufacturers are creating nanostructured solar cells that are better at capturing energy in the form of photons from the sun. However, as photons are converted to electrons in these solar cells, unwanted heat is generated in the device, significantly reducing its efficiency.
“If we can understand how these energy conversion processes work inside nanostructured solar cells, we can improve their efficiency and lower their cost,” says Thompson, who also is a fellow of the college’s Grainger Institute for Engineering.
Thompson is an experimentalist, and part of his work involves developing better experimental tools for probing heat flow at the nanoscale. For example, he fabricates nano-sized devices that provide excellent sensitivity for measuring very tiny heat currents.
He’s particularly interested in studying thermal radiation and radiative heat flow, a mode of heat transfer that’s especially challenging to measure at the nanoscale.
“Thermal radiation usually isn’t the dominant mode of heat transfer at room temperature, so if you’re trying to measure a radiative heat current, that signal can often be drowned out by other modes of heat transfer,” he says. “So I conduct my experiments in a high-vacuum, low-noise environment to eliminate these other modes of heat transfer and improve the signal-to-noise ratio.”
Thompson earned his bachelor’s degree in mechanical engineering from the Georgia Institute of Technology in 2012. A heat transfer course taught by Professor Baratunde Cola kindled Thompson’s interest in this field, and he joined the Cola’s NanoEngineered Systems and Transport Lab as an undergraduate at Georgia Tech.
Thompson then enrolled at the University of Michigan, where he earned a master’s degree in 2014 and a PhD in 2018. As a graduate student in the Nanoscale Transport Lab, he researched radiative thermal transport at the nanoscale using high-resolution calorimetry.
After his PhD, he joined UW-Madison. He says he was attracted by the outstanding facilities and research infrastructure at UW-Madison, as well as by the supportive, down-to-earth faculty in the College of Engineering.
“As a large university, I think UW-Madison really has every resource you could want, and it offers resources that other universities don’t have,” he says. “For example, UW-Madison has really great clean room facilities, which is essential for my research.”
In fall 2019, Thompson is co-teaching the elementary heat transfer course. He will take over teaching the course in spring 2020, and he’s excited to share his passion for the topic with students. “I think heat transfer is really interesting because it is fundamental to any energy conversion technology,” he says.
Author: Adam Malecek