报告人：吕鹏宇

报告题目：终极稳定的水下超疏水状态（Ultimate Stable Underwater Superhydrophobic State）

邀请人：胡海豹 教授

报告时间：11月21日上午10:30-11:30

报告地点：航海学院201会议室

报告简介：Superhydrophobicity of underwater structured surfaces is crucial to their functionalities like drag reduction, where a large area fraction of liquid-gas interfaces in the pinnedCassie-Baxter stateis required. However, various factors, such as pressurization, air diffusion, and liquid flow, will cause the instability of liquid-gas interfaces, leading to either wetting transition to the fully wetted Wenzel state or protrusion of bubbles into the liquid, which significantly influences the underwater performance. In the current work, stability of liquid-gas interfaces is investigated and various wetting states are directly observed and measured by confocal microscopy. The metastable state dynamically evolves owing to the air diffusion, which is extensively quantified under different ambient pressure conditions. A similarity law along with a characteristic time scale is derived which governs the lifetime of the air pockets. Air exchange between air pockets and surrounding water is therefore proved to be significant to the stability of liquid-gas interfaces. We then theoretically demonstrate and experimentally achieve an ultimate stable state on underwater superhydrophobic surfaces with arbitrary rough structures through the synergy of mechanical balance and chemical diffusion equilibrium across the interfaces. The equilibrium morphology of the meniscus can be tuned by adjusting the dissolved gas saturation degree under a given liquid pressure. The current results provide a further understanding of long-term stability of underwater superhydrophobicityand also promote their functionalities in practical applications.

报告人简介：吕鹏宇，男，2015年在北京大学工学院力学与工程科学系获得固体力学博士学位，2015年至2017年在荷兰屯特大学流体物理课题组进行博士后研究。现任北京大学工学院、北京大学工程科学与新兴技术高精尖创新中心助理研究员。主要从事流固耦合界面力学的研究，包括微结构表面浸润状态与浸润转变、气泡形貌演化、流体界面滑移特性、液滴蒸发溶解行为等研究方向，在《Physical Review Letters》、《Physics of Fluids》、《力学进展》等国内外主流期刊上发表SCI论文18篇（ESI高被引论文1篇），他人SCI引用140多次，国际专利1项，国家实用新型专利2项，2015年获得北京大学优秀博士学位论文荣誉。