UCLA

The processes of phase transformation continue to affect our natural and industrial worlds in a range of scales from large-scale lava flows in nature to micro-and nano- scale applications in industry. Enhancement of the knowledge framework of these processes and understanding the accompanying physical phenomena are keys to resolve challenges in scientific research and obtain rational engineering evaluations for a wide range of industrial application such as 3D printing, rapid prototyping, thermal spray coating, power plants, aerospace and turbine industries. A great deal of work has been done in the past few decades on these matters, and significant progress has been made; however, much of it remains unraveled. The main difficulty stems from the intertwined effect of heat transfer, fluid dynamics, and phase change physics with the combination of complex wetting behaviors of the contact-line. In this thesis, we focus on solidification and condensation near the contact-line. For solidification near the contact-line, we have studied the onset of solidification and its relevant physical parameters and explored ways to delay the start of solidification inspired by the unique ice-resisting abilities of penguin feathers and certain plant leaves. The dynamics of solidification and spreading is also studied and new hypothesis is introduced to explain the contact-line pinning due to solidification. Finally, in condensation near the contact-line, we have introduced a novel biphilic surface with large scale cost-effective manufacturing process and analyzed and compared its heat transfer efficiency and water droplet mobility to traditional hydrophobic and hydrophilic structures.