Chillin’ out: Innovating effective thermal management technologies through solid-liquid-vapor nanointeractions

When you think of the term “climate change,” it’s easy to think big. After all, this is an unmatched global crisis that knows no national borders. However, when you think of solutions to climate change, it may serve you to look smaller—in fact, at nano-levels. Much of our wasted energy may be resolved by seemingly tiny details.

Dr. Damena Agonafer from the McKelvey School of Engineering studies such details at his Nanoscale Energy and Interfacial Transport (NEIT) Lab, where he focuses on the design of micro-and nano-engineered surfaces to improve energy storage and thermal transport. Agonafer’s research explores energy (heat) transfer on surfaces through phase change. When a drop of water evaporates from your skin, it carries with it some heat energy, cooling you off. Agonafer and his team are developing ways to maximize the efficiency of this cooling effect for tech, which has huge implications for global energy consumption.

Data centers consume 2% of electricity in the US and their demand for power is rising parallel to microchip advancement. As chips advance, they require more transistors and higher power densities, creating a thermal challenge on how to cool them compactly. This, Agonafer believes, will require integrating phase change heat transfer (like evaporation) into tech. The lab is hopeful that the evaporative technology it is developing can improve waste heat recovery by up to 80 times compared to today’s state-of-art air cooling methods.

To understand this next-generation technology, we must first understand the physics of droplets. In nature, you’ll find raindrops to be hemispherical (i). These require larger amounts of energy to evaporate because the droplets are millimeters large with contact angles of nearly 90°, which presents high resistance to evaporation across the droplet. The smaller the contact angle, the less energy required to cause evaporation. Agonafer finds that smaller, asymmetrical droplets (iii) evaporate far easier.

The NEIT Lab is engineering ways for liquid to rest on surfaces with asymmetrical droplet shapes by developing unique surfaces that efficiently organize such droplets and optimize the evaporation process. While not a systems-level change, microscopic technological details like this are critical to reduce our energy consumption and decelerate climate change.

Agonafer’s group is also expanding into systems-level thinking. For instance, they know that with less thermal resistance to evaporation, there is more energy that can be diverted from the system as exergy (the maximum amount of energy from a system). This energy can be applied to other uses—for instance, to heat up a nearby building. High-tech systems like these are how Agonafer envisions integrating and applying his surface nanostructure advancements.

The group has patents for chip cooling systems and power modules for hydroelectric vehicles, and it recently received funding from the Office of Naval Research to translate the patent into technology. The Agonafer group also just obtained funding from Google to explore applications on cooling heterogenous integrated chips.

Agonafer was recently awarded the ASME Early Career Award and the NSF CAREER Award.

Featured publications

• Agonafer, Damena D., et al. “Burst Behavior at a Capillary Tip: Effect of Low and High Surface Tension.” Journal of Colloid and Interface Science, vol. 455, 2015, pp. 1–5., doi:10.1016/j.jcis.2015.05.033.
• Agonafer, Damena D., et al. “Porous Micropillar Structures for Retaining Low Surface Tension Liquids.” Journal of Colloid and Interface Science, vol. 514, 2018, pp. 316–327., doi:10.1016/j.jcis.2017.12.011.
• Li, Junhui, et al. “Investigation of the Confinement Effect on the Evaporation Behavior of a Droplet Pinned on a Micropillar Structure.” Journal of Colloid and Interface Science, vol. 555, 2019, pp. 583–594., doi:10.1016/j.jcis.2019.07.096.
• Ma, Binjian, et al. “Evolution of Microdroplet Morphology Confined on Asymmetric Micropillar Structures.” Langmuir, vol. 35, no. 37, 2019, pp. 12264–12275., doi:10.1021/acs.langmuir.9b01410.
• Nahar, Mun Mun, et al. “Review Article: Microscale Evaporative Cooling Technologies for High Heat Flux Microelectronics Devices: Background and Recent Advances.” Applied Thermal Engineering, 2021, p. 117109., doi:10.1016/j.applthermaleng.2021.117109.
• Shan, Li, et al. “Experimental Investigation of Evaporation from Asymmetric Microdroplets Confined on Heated Micropillar Structures.” Experimental Thermal and Fluid Science, vol. 109, 2019, p. 109889., doi:10.1016/j.expthermflusci.2019.109889.
• Shan, Li, et al. “Investigation of the Evaporation Heat Transfer Mechanism of a Non-Axisymmetric Droplet Confined on a Heated Micropillar Structure.” International Journal of Heat and Mass Transfer, vol. 141, 2019, pp. 191–203., doi:10.1016/j.ijheatmasstransfer.2019.06.042.
• Shan, Li, et al. “Numerical Investigation of Shape Effect on Microdroplet Evaporation.” Journal of Electronic Packaging, vol. 141, no. 4, 2019, doi:10.1115/1.4044962.

Featured patent

• US Patent Application No. 17/267,539 entitled “Methods and Systems for Evaporation of Liquid From Droplet Confined on Hollow Pillar.”  
• US Patent Application No. 17/203,677 entitled “Systems and Methods for Forming Micropillar Array.”