Zhu Zhongpeng, professor and doctoral supervisor at Suzhou Institute for Advanced Research (SIAR), University of Science and Technology of China (USTC), has made substantial progress in droplet impact behavior at super-lyophilic interfaces and published his findings in the Journal of the American Chemical Society (JACS) under the title "Ultrafast Impact Superspreading on Superamphiphilic Silicon Surfaces for Effective Thermal Management".

Spray cooling is a uniform and efficient heat dissipation method mainly based on the impact of coolant droplets on overheated solid surfaces, and characterized by efficient heat dissipation achieved by means of liquid evaporation phase change. While it has been widely applied in the fields of electronic manufacturing, metal smelting, automobile manufacturing and thermal power generation, splashing and retracting usually occur in the process of droplet impact and affect the uniformity of interface heat dissipation during spray cooling, as well as heat dissipation efficiency. However, it is expected to be solved by adjusting interface wettability to have controllable droplet impact spreading behaviors.

Previous studies on droplet impingement behavior mainly focused on hydrophilic, hydrophobic and superhydrophobic interfaces, where droplets often show splashing and retracting dynamics due to low solid-liquid interactions. The present study reported that ultrafast impact spreading behaviors (the spreading time was only about 3. 0 ms) of water droplets on superamphiphilic silicon wafer surfaces effectively suppressed droplet splashing and retraction, and that a precursor film existed during the spreading process. Not only that, it also found that the precursor film at the spreading edge was induced by the hydrophilic/hydrophobic domains at the nanoscale, and it effectively improved the liquid flux at the spreading edge and inhibited the splashing behavior. The precursor film also reduced the horizontal Laplace pressure at the spreading edge, so contraction force decreased when droplets spread to the maximum area, thus largely inhibiting droplet retraction. Given the impact super-spreading behavior of droplets on a super-amphiphilic silicon wafer surface, the uniformity and efficiency of evaporation heat dissipation were obviously enhanced in the spray cooling process, and meanwhile, the controllable impact super-spreading behavior played an important role in reducing pesticide waste, improving inkjet printing accuracy and manufacturing functional films by a drop coating method.

Schematic diagram of water droplet impingement superspreading

This paper was jointly completed by Zhu Zhongpeng, Research Scientist & Doctoral Supervisor at SIAR, and Researcher Tian Ye and CAS member Jiang Lei of Technical Institute of Physical and Chemistry. Zhu Zhongpeng is the first author and Tian Ye is the corresponding author.

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