Fazle Rabbi Kazi, Khodakarami Siavash, Ho Jin Yao, Hoque Muhammad Jahidul, Miljkovic Nenad
Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA.
School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Republic of Singapore.
Nat Commun. 2025 Jan 28;16(1):1105. doi: 10.1038/s41467-025-56338-3.
Condensation is a vital process integral to numerous industrial applications. Enhancing condensation efficiency through dropwise condensation on hydrophobic surfaces is well-documented. However, no surfaces have been able to repel liquids with extremely low surface tension, such as fluorinated solvents, during condensation, as they nucleate and completely wet even the most hydrophobic interfaces. Here, we introduce a surface functionalization methodology that enables dropwise condensation of fluorinated refrigerants. This approach, compatible with various substrates, combines low contact angle hysteresis Parylene-C with low surface energy silane (P-HFDS) using a highly scalable atmospheric vapor phase deposition technique. Our experimental results demonstrate that the omniphobic P-HFDS coating facilitates dropwise condensation of both natural refrigerants (water, ethanol, hexane, pentane) and synthetic low-global-warming-potential refrigerants (HCFO R1233zd(E) and HFO R1336mzz(Z)) with surface tension as low as 14.6 mN m at 25°C. The P-HFDS coating improves condensation heat transfer coefficients by 274%, 347%, 636%, and 688% for ethanol, hexane, pentane, and R1233zd(E), respectively, compared to filmwise condensation on uncoated metal surfaces. Additionally, the coating demonstrates long-term durability, sustaining steady dropwise condensation for 170 days without apparent degradation. This work pioneers stable dropwise condensation of multiple refrigerants on a structure-less surface, offering a durable, substrate-independent, and scalable solution for low surface energy coatings.
冷凝是众多工业应用中不可或缺的关键过程。通过在疏水表面上的滴状冷凝来提高冷凝效率已有充分的文献记载。然而,在冷凝过程中,没有任何表面能够排斥表面张力极低的液体,如氟化溶剂,因为它们会成核并完全润湿即使是最疏水的界面。在此,我们介绍一种表面功能化方法,可实现氟化制冷剂的滴状冷凝。这种方法与各种基材兼容,使用高度可扩展的常压气相沉积技术,将低接触角滞后的聚对二甲苯-C与低表面能硅烷(P-HFDS)相结合。我们的实验结果表明,这种超疏水的P-HFDS涂层有助于天然制冷剂(水、乙醇、己烷、戊烷)和合成的低全球变暖潜能制冷剂(HCFO R1233zd(E)和HFO R1336mzz(Z))在25°C时表面张力低至14.6 mN m的滴状冷凝。与未涂层金属表面上的膜状冷凝相比,P-HFDS涂层分别使乙醇、己烷、戊烷和R1233zd(E)的冷凝传热系数提高了274%、347%、636%和688%。此外,该涂层具有长期耐久性,可在170天内维持稳定的滴状冷凝而无明显降解。这项工作开创了在无结构表面上多种制冷剂的稳定滴状冷凝,为低表面能涂层提供了一种耐用、与基材无关且可扩展的解决方案。