Interfacial water from molecular to mesoscopic scale and its relation to tunable hydrophobicity

弗吉尼亚联邦大学的Alenka Luzar获得了化学系化学理论、模型和计算方法项目的一项奖励，以开展关于具有拓扑和化学异质性的表面的可逆润湿转变和润湿性的研究。该方法包括统计力学的理论和模拟技术相结合，并开发计算算法来处理纳米受限空间中水的界面性质。正在研究三个具体问题：（1）超疏水性表面上的电场或压力诱导转变，以实现对比的Cassie和Wenzel状态之间的可逆切换;（2）电极上的纳米液滴驱动，以提供液滴的详细且自洽的微观图像和电极在施加电压下的动态响应，在连续介质物理学充其量只能提供非常粗略的预测的条件下;（3）探索化学非均质基底上表面力加和性的程度，以解决如何从纯表面之间的力预测混合表面之间的力。该研究对包括材料科学、工程和生物学在内的许多学科产生了广泛的影响。通过外部刺激对表面疏水性的智能控制的分子水平的理解可以在纳米流体学和电光学中找到现实世界的应用。第一个主题阐明了在电和/或压力控制下，材料的抗润湿性和亲水性行为之间的可逆切换是否可以在纳米级上实现，以及所涉及的时间尺度是什么。第二个主题是电控纳米光学元件的设计。 他们想了解可调光学器件是否可以小型化到纳米级，以及与宏观器件相比，它们的基本优势或挑战是什么。 第三个主题影响到纳米技术中自组装材料的研究，以及生物物理学。

Alenka Luzar of Virginia Commonwealth University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division to carry out research on reversible wetting transitions and nanowetting of surfaces with topological and chemical heterogeneities. The methodologies include a combination of theory and simulation techniques in statistical mechanics and development of computational algorithms to deal with interfacial properties of water in nanoconfined spaces. Three specific problems are being investigated: (1) electric field or pressure-induced transitions on superyhdrophobic surfaces to achieve reversible switching between contrasting Cassie and Wenzel states; (2) nanodroplet actuation on an electrode to provide a detailed and self-consistent microscopic picture of drop and electrode dynamic responses under applied voltage, at conditions where continuum physics offers at best very crude predictions; and (3) probing the extent of surface force additivity on chemically heterogeneous substrates to address how well they can predict forces between mixed surfaces from those between pure ones.The research has broad impact on many disciplines including materials science, engineering, and biology. Molecular level understanding of intelligent control of surface hydrophobicity by external stimuli can find real-world applications in nano-fluidics and electro-optics. The first topic elucidates if reversible switching between wetting-resistant and hydrophilic behavior of a material is achievable at the nanoscale under electric and/or pressure control, and what are the time scales involved. The second topic concerns the design of nano-sized optical elements under electric control. They want to learn if tunable optical devices can be miniaturized to the nanoscale level, and what could be the essential advantages or challenges in comparison to macroscopic ones. The third topic impacts research into self-assembling materials studied in nanotechnology, as well as biophysics.