Patterned Quasi‐Liquid Surfaces for Condensation of Low Surface Tension Fluids

• Published in: Advanced functional materials 2024-08, Vol.34 (33), p.n/a
• Main Authors: Boylan, Dylan, Monga, Deepak, Guo, Zongqi, Dosawada, Pavan Sai, Shan, Li, Wang, Pengtao, Dai, Xianming
• Format: Article
• Language: English
• Subjects: Beetles; Condensation; Contact angle; Ethanol; Fluorination; heat transfer; Heat transfer coefficients; Hexanes; Hysteresis; Liquid surfaces; low surface tension; Quasi‐liquid surface; Surface energy; Surface tension; Thermal energy; Wettability
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202400194

Extensive research concerns dropwise condensation of low surface tension fluids to promote energy efficiency and decarbonization in thermal energy systems. However, it is challenging as these fluids typically result in filmwise condensation. Drawing inspiration from the Namib desert beetle that enhances condensation through patterned wettability, conventional beetle‐inspired surfaces excel in water condensation but flood when condensing low surface tension fluids. In this work, a patterned quasi‐liquid surface is reported that achieves exceptional dropwise condensation of low surface tension fluids. The surface consists of alternating stripes with low surface energy, that is, a perfluoropolyether (PFPE) and fluorinated quasi‐liquid surface (FQLS), that shows ultralow contact angle hysteresis for ethanol and hexane. The PFPE stripes are slightly more slippery, acting as slippery bridges that accelerate droplet coalescence and removal. It is experimentally demonstrated that the striped PFPE‐FQLS pattern exhibits a heat transfer coefficient 85%, 330%, and 550% higher than that of PFPE, fluorinated silane, and filmwise condensation, respectively. This study reveals that a high contact angle is desired to sustain dropwise condensation, irrespective of contact angle hysteresis. These findings provide a new paradigm for promoting the dropwise condensation of low surface tension fluids and offer valuable insights into surface design for energy sustainability. Beetle‐inspired designs with special wettability have potential to promote energy efficiency and decarbonization in thermal energy systems. Existing beetle‐inspired surfaces fail for low surface tension fluids. Here, dropwise condensation of low surface tension fluids is achieved by chemically patterned PFPE‐FQLS, with large contact angles but different hysteresis. PFPE‐FQLS shows a heat transfer coefficient 330% higher than the fluorinated silane surface.