Zhu Yihao, Tso Chi Yan, Ho Tsz Chung, Leung Michael K H, Yao Shuhuai
School of Energy and Environment, City University of Hong Kong, Kowloon Tong, Kowloon 999077, Hong Kong.
Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong.
ACS Appl Mater Interfaces. 2021 Mar 10;13(9):11470-11479. doi: 10.1021/acsami.0c22055. Epub 2021 Feb 25.
Benefitting from the coalescence-induced droplet jumping on superhydrophobic surfaces, the condensing droplets on heat exchangers can be removed efficiently, significantly improving the condensation heat-transfer performance of various thermal applications. However, the enhancement of droplet jumping height and self-removal to further improve the condensation heat-transfer performance of the thermal applications remains a challenge due to considerable interfacial adhesion caused by the inevitable partial-Wenzel state condensing droplets on superhydrophobic surfaces. In this study, a biphilic nanostructure is developed to effectively improve the droplet jumping height by decreasing the interfacial adhesion with the formation of Cassie-like droplets. Under atmospheric conditions, ∼28% improvement of droplet jumping height is achieved on a biphilic surface compared to that of a superhydrophobic surface. Additionally, the droplet contact electrification on biphilic surfaces discovered in this work allows the droplets to jump ∼137% higher compared with that under atmospheric conditions. Furthermore, the droplet jumping and electrification mechanisms on the biphilic surface are revealed by building a theoretical model that can predict the experimental results well. Apart from being a milestone for the droplet jumping physics development on biphilic nanostructures, this work also provides new insights into the micro-droplet discipline.
受益于超疏水表面上聚并诱导的液滴跳跃，热交换器上的冷凝液滴能够被有效去除，显著提高了各种热应用的冷凝传热性能。然而，由于超疏水表面上不可避免的部分Wenzel态冷凝液滴导致的相当大的界面附着力，提高液滴跳跃高度和自去除能力以进一步改善热应用的冷凝传热性能仍然是一个挑战。在本研究中，开发了一种双亲纳米结构，通过形成类Cassie液滴来降低界面附着力，从而有效提高液滴跳跃高度。在大气条件下，与超疏水表面相比，双亲表面上的液滴跳跃高度提高了约28%。此外，本工作中发现的双亲表面上的液滴接触起电使得液滴跳跃高度比大气条件下高出约137%。此外，通过建立一个能够很好预测实验结果的理论模型，揭示了双亲表面上的液滴跳跃和起电机理。除了作为双亲纳米结构上液滴跳跃物理学发展的一个里程碑外，这项工作还为微滴学科提供了新的见解。
