The United States military is turning up the heat in its search for new scalable technologies that will meet its needs for electronics devices that are smaller, scalable and keep their cool.

Even with the added pressures of a compressed time frame and working in microscale, Nebraska Engineering researchers are poised to build on their track records as innovators and leaders in heat transfer and thermal management.

The first, 18-month phase of a four-year Defense Advanced Research Projects Agency grant, with Northrop Grumman as the lead, is underway with DARPA funding totaling $9,234,025, of which Nebraska will receive about $1.6 million. Nebraska’s total could increase to more than $2.6 million over four years.

The grant supports development of scalable technologies to control “hot spots” in future electronics architectures for the U.S. Department of Defense.

“What’s unique is that to make them smaller, we’re looking at stacking chips in three dimensions instead of traditional two-dimensional layouts,” said Craig Zuhlke, co-director of the Center for Electro-Optics and Functionalized Surfaces and lead investigator for the Nebraska team and an expert in the field of functionalized surfaces. “This creates different thermal modes throughout the microsystem that require enhanced thermal management. Our focus is on the high-power-density regions.”

The project, “Miniature Integrated Thermal Management Systems for 3D Heterogeneous Integration,” or Minitherms3D, brings together researchers from several corporate partners and universities, including Nebraska.

The team also includes George Gogos, center co-director and Wilmer J. and Sally Hergenrader Chair of Mechanical Engineering, and Jeffrey Shield, Robert W. Brightfelt Professor of Engineering and department chair of mechanical and materials engineering.

Gogos said the Nebraska-based center is “uniquely positioned” to make this research a success, with decades of experience as a leader in functionalized surfaces and heat transfer, and state-of-the-art equipment and resources.

“They aren’t looking to make just a small, incremental step in manufacturing and design; the idea is to make a big leap,” said Gogos, who also directs the Nebraska Center for Energy Sciences Research. “To get there, they will be using the technology and expertise we’ve developed.”

Shield said unlike most projects, this DARPA grant requires researchers to “hit the ground running.”

“We don’t have the luxury of an incubation period,” Shield said. “Northrop knew that we could step in and make progress right away with everything we have in place — including our laser technologies and techniques in heat transfer, thermal management and functionalized surfaces that are known throughout the world and a fully functioning team of more than 30 researchers from many disciplines across our college and university.”

Additionally, Zuhlke said, the foundation for this DARPA project was built on continuous base funding from the Office of Naval Research and DoD since 2015. That funding has allowed the center to acquire state-of-the-art lasers and equipment to conduct pioneering research into femtosecond laser surface processing and its applications, which Zuhlke said built the foundation for this DARPA project.

By utilizing a state-of-the-art femtosecond laser to alter — or “functionalize” the surfaces — Nebraska researchers also aim to make the new chip stacks more durable and versatile.

“One of the important aspects is being able to have fine control of where it is applied. There are certain regions that need to be processed and certain regions that can’t be processed,” said Zuhlke, associate professor of electrical and computer engineering. “There’s an ease of application with FLSP compared to other techniques. We can make this tunable to a specific application.”

The initial phase is set to end in May 2025, when DARPA will evaluate the project and determine whether to fund a second, 18-month phase focused on demonstrating thermal management capabilities.

In a third 12-month phase, the team would demonstrate system level thermal resistance and heat rejection in a simulated application.

Current manufacturing methods are smaller scale and complicated, and often are not environmentally sound, Gogos said. Their chip architectures are also much larger than DARPA wants in its next-generation electronics.

Unoptimized heat transmission and rejection also result in the large overall size of thermal-management hardware. This limits growth in system capabilities, particularly in radio frequency systems image analysis, and high-performance computing applications such as artificial intelligence and machine learning.

This DARPA project aims to create five-tier, 3D chip stacks with total heat dissipation of more than 6.8 kilowatts. Each stack, Gogos said, should be roughly two inches by two inches and a half-inch thick and will feature a heat rejection system of less than 0.006 cubic meters — roughly the same volume as in a basketball.

Among the possible DoD applications are advanced radar processing for unmanned aerial vehicles and high-speed data analysis in mobile and edge computing environments.

The drive to create these smaller structures, however, will inevitably generate its own set of problems.

“The electronics industry wants to make everything smaller and smaller, but with the same or even a greater amount of power being generated in a smaller volume. That’s what creates these ultra-tiny hot spots in these 3D stacks,” Shield said. “If you can’t get rid of that heat, it won’t matter that it takes up less space.”

Citing Zuhlke’s career trajectory as an example, Gogos said funding from the project and the recent formation of a startup company, Integrated Functionalized Materials, can be important to strengthening Nebraska’s workforce.

“We have a lot of graduate students, including 12 doctoral candidates, in this collaborative effort, and many are just like Craig, who came here, got his undergraduate and doctoral degrees, stayed in the College of Engineering and now is a key leader in CEFS,” Gogos said.

“Through programs like the Nebraska Research Initiative, the State of Nebraska has invested generously in supporting research endeavors at UNL and Nebraska Engineering, and we’re seeing the dividends in grants like this one from DARPA that are allowing us to develop and retain homegrown talent and build up the future.”

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