CAREER: Diffusive and Convective Gas Dissolution over Super-Hydrophobic Surfaces

超疏水表面最初是在荷叶上发现的，最近显示出作为下一代多功能材料的巨大潜力。当浸入液体时，这些表面会在表面纹理之间形成一层气体，从而使许多行业受益，例如节省海上运输的能源，保护海底结构免受腐蚀和生物污染。然而，有益气体可能会溶解在环境液体中，并且可能只能持续有限的时间，这极大地限制了超疏水表面的实际应用。该项目旨在通过创新实验了解气体的溶解过程，并制定新的策略来延长气体的寿命。研究工作与教育和推广计划很好地结合在一起，包括五项活动：本科生领导的原创研究，高中生暑期研讨会，K-12学生的桌面实验，当地自主水下航行器制造商的班级旅行，以及新英格兰东南部地区海洋工业的技术展示。同时测量质量通量、速度场和气体浓度场这三个决定气体从超疏水表面向液体溶解的关键参数的实验研究还很缺乏。本项目通过结合反射干涉对比显微镜、平面激光诱导荧光抑制和全息粒子成像测速这三种先进的光学技术，填补了这一空白，测量了三个参数。第一个目的是研究固定液体中的扩散气体传递。结果将揭示液体中的气体浓度如何变化并最终影响质量通量。通过系统地改变结构参数（高度、波长和气体含量），建立气体寿命的预测模型。第二个目标是研究层流和湍流中的对流气体转移。通过改变试样的滑移长度，提出了新的舍伍德数在滑移边界上的标度模型。第三个目标是通过研究四种被动和主动方法对天然气寿命的影响来解决气体溶解问题，这四种方法分别是：纳米尺度的粗糙度、可重新进入的几何形状、通过多孔材料注入气体以及过饱和水的气体转移。这个项目将是革命性的，并推进我们对新材料复杂边界的传质、界面稳定性和流动动力学的基本理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Superhydrophobic surfaces, initially found on lotus leaves, have recently shown great potential to be the next generation of multi-function materials. These surfaces trap a layer of gas between the surface textures when immersed in liquid, and consequently benefit many industries from saving energy in maritime transport, to protecting undersea structures from corrosion and biofouling. However, the beneficial gas could be dissolved in ambient liquid and may last only for a limited amount of time, significantly limiting the real-world applications of superhydrophobic surfaces. This project aims to understand this gas dissolution process through innovative experiments and develop new strategies to extend the longevity of gas. The research efforts are well integrated with an education and outreach plan including five activities: undergraduate student-lead original research, summer workshop for high-school students, table-top experiments for K-12 students, class trip to a local autonomous underwater vehicle manufacturer, and technology showcase to marine industry in the Southeastern New England area.There is a lack of experimental studies which simultaneously measure mass flux, velocity field and gas concentration field, which are three key parameters that govern the dissolution of gas from the superhydrophobic surfaces to the liquid. This project fills this gap and measures the three parameters by combining three advanced optical technologies: Reflective Interference Contrast Microscopy, Planar Laser-Induced Fluorescence with Inhibition, and Holographic Particle Image Velocimetry. The first objective is to investigate the diffusive gas transfer in stationary liquid. The results will reveal how gas concentration in liquid changes and ultimately affects the mass flux. By systemically varying the texture parameters (height, wavelength, and gas fraction), predictive models of gas longevity will be established. The second objective is to examine the convective gas transfer in laminar and turbulent flows. By varying the slip length of the samples, new scaling models of Sherwood number over slip boundaries will be proposed. The third objective is to combat the gas dissolution issue by studying the impacts of four passive and active methods on gas longevity: nano-scale roughness, re-entrant geometry, gas injection through a porous material, and gas transfer from supersaturated water. This project will be transformative and advance our fundamental understanding of mass transfer, interfacial stability, and flow dynamics at complex boundaries of novel materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.