Zuankai Wang’s landmark achievement shatters the limits of the Leidenfrost effect, a 266-year-old puzzle in thermal cooling. Wang’s innovation, the Structured Thermal Armor (STA), ingeniously combines insulation, conduction, and hydrodynamics, enabling efficient liquid cooling even at extreme temperatures above 1150°C. His breakthrough extends superwettability to unprecedented levels, promising transformative impacts on aircraft, nuclear plants, and beyond.
Which wall does your research break?
Our research work solves a 266-year historically unsolved challenge in thermal cooling imposed by the Leidenfrost effect.The Leidenfrost effect is a physical phenomenon discovered in 1756, which refers to the levitation of drops on a surface that is significantly hotter than the liquid’s boiling point. The insulating vapor layer produced from the evaporating liquid dramatically reduces heat transfer performances at high temperatures, which makes thermal cooling on the hot surface ineffective. This formidable effect has perplexed high-temperature liquid cooling for over two centuries, as evidenced by the onset of the Fukushima nuclear power plant disaster. To date, the highest temperature point that suppresses the Leidenfrost effect, referred to as the Leidenfrost point, is around 600°C, which is also achieved at the expense of heat transfer performances. Searching for novel strategies to break the wall to the Leidenfrost effect for achieving efficient thermal cooling remains a long-standing challenge. Publishing in Nature, we developed a novel Structured Thermal Armor (STA) in which we counterintuitively introduce thermally insulating materials into thermally conductive structures to endow superwetting and evaporation of liquid even over 1150°C and hence dramatically boost the Leidenfrost point without sacrificing heat transfer. We also demonstrate that we can achieve efficient liquid cooling in the whole temperature range (100°C-above 1150°C), only limited by the melting of materials). The STA can be made flexible, which permits its facile attaching to various substrates otherwise challenging to structure directly and hence endows ultra-highly efficient liquid thermal cooling. Conquering this century-old physical effect dramatically extends the temperature limit of superwettability, one of the top ten emerging technologies selected by IUPAC 2021 chemistry, and also would provide a paradigm shift in thermal cooling, especially in extreme conditions such as aircraft, turbine, nuclear power plant, chip cooling and so on.
What inspired or motivated you to work on your current research or project?
First, I was fascinated by the Leidenfrost effect, which is vividly exemplified by the rolling and dancing of cold-water droplets on hot pots and the mystery of splitting molten iron with bare hands without being hurt. In addition to these magic wonders, it also abounds huge potentials such as in drag reduction and liquid mixing. On the other hand, the Leidenfrost effect is a formidable enemy that has perplexed high-temperature liquid cooling for over two centuries, as evidenced by the onset of the Fukushima nuclear power plant disaster. Currently, over 90% of energy consumption and utilization involves thermal processes and there is a large demand for effective cooling technologies. Second, I was also interested in water, the origin of our life. Water has very high latent heat and is ubiquitous. However, phase change heat transfer using water (and other liquids) suffers a historic challenge, the Leidenfrost effect, which nearly invalids the liquid cooling technologies or achieves heat transfer at the cost of dramatic water consumption. Particularly, thermal cooling at high temperatures is susceptible to the Leidenfrost effect. Focusing on the above problems, reporting in Nature Physics in 2016, we realized the spontaneous transfer of liquid droplets from the low-heat-transfer Leidenfrost region to the high-heat-transfer boiling region, thus boosting the heat transfer coefficient by 13 times. Moving forward and by taking advantage of our multidisciplinary expertise in surface science, hydro- and aero-dynamics, thermal cooling, materials science, physics, energy and engineering, we came up with the STA with key elements that have contrasting thermal and geometrical properties. The rational design for the STA superimposes robust, conductive, protruding pillars that serve as thermal bridges for promoting heat transfer; an embedded thermally insulating membrane designed to suck and evaporate the liquid; and underground U-shaped channels that evacuate the vapor. We are very lucky to make this breakthrough.
In what ways does society benefit from your research?
The impact of our work is far-reaching. First, in thermal cooling, current thermal cooling strategies under extremely high temperatures mainly adopt air cooling owing to the occurrence of the Leidenfrost effect, especially for applications in aero-engines and space-engines, and next-generation nuclear reactors. Our work subverts this landscape, enabling efficient liquid cooling even under extreme environments. Second, this breakthrough can also lead to significant promotion in addressing the ultra-high heat flux problem, such as thermonuclear fusion, nuclear plants, and integrated chips. Third, in 2021, superwettability was listed as one of the Top 10 Emerging Technologies by the International Union of Pure and Applied Chemistry (IUPAC). However, current superwettability only manifests in a very limited temperature range, and the breakthrough dramatically extends the temperature range of superwettability above 1000°C, which will open up limitless applications in chemistry and beyond.