CAREER: Fundamental Studies to Advance the Science and Engineering of Water at Negative Pressures

职业：推进负压下水科学与工程的基础研究康奈尔大学智力优势：本提案的目标是为液态水的物理状态提供知识和潜在的实际应用，这一物理状态在实验上只有很少的探索，在技术上几乎完全没有开发：负压下液态水的机械稳定和热力学亚稳态。众所周知，液态水的强度非常大：研究表明，在压力低至-10兆帕的情况下，植物在蒸腾过程中会移动水分；在实验室中，它被置于-102兆帕的压力下。尽管如此，人类还没有技术在显著的负压（即-1.5 MPa）下开采过水。负压状态还包含了关于水在整个液体状态下的特性的重要信息：分子模型表明，热力学和动力学异常不仅在这种状态下持续存在，而且变得更加引人注目，并与流体的不寻常分子特性紧密耦合。尽管科学界对此非常感兴趣，但在负压下水的热力学、动力学和结构特性实际上还没有通过实验绘制出来。由于先进的制造工具的出现，以及我们实验室最近的一种新方法的发展，这项实验工作已经成熟，可以将液态水深入到负压状态，该方法基于液态水通过分子膜与亚饱和蒸汽的热力学耦合。研究人员将利用这些工具建立一个微流控平台，以前所未有的精度操纵和研究张力下的水。他们的研究将描绘水的拉伸状态的热力学、动力学和结构特性，重点是阐明宏观特性的分子起源。这些测量将使他们能够解决有关液态水性质的一些最深刻的悬而未决的问题，并填补这种不寻常物质状态的科学和工程知识基础上的一个主要空白。这一努力也很及时，因为它将与快速发展的水计算模型创建一个动态接口（见合作函）。更广泛的影响：这项研究有可能为水管理技术开辟一个新的运作机制：热管、土壤芯、环境修复、用于分离和净化的微流控芯片实验室系统，以及用于低温燃料电池的呼吸电极。在所有这些技术中，水芯或膜都是在正压力或非常轻微的负压（-0.1 MPa）下调节水的流动，由于无法在大张力下控制水，其功能受到严重限制。根据这里提出的发展，这些传质率可以增加几个数量级，操作参数（尺寸、温度、相对湿度）的范围可以大大扩大。当今工程师应用领域令人兴奋的变化使我们有义务更新课程和教学模式。调查员描述了修改现有课程组成部分并在本科和研究生阶段增加新课程的计划。提出了解决现代工程课程中的关键挑战的计划：1)维持基本概念的有效教学，同时更新背景，包括更多与新背景相关的材料，如微化学技术和生物工程；2)鼓励创新使用技能，这样未来的工程师就可以发明和操作下一代技术；3)鼓励将研究作为本科和研究生教育的重要组成部分和职业选择。随着新技术的出现，教育公众，特别是儿童了解其功能的永恒（如热力学）和及时（如微观和纳米技术）方面也很重要。在第七部分，我建议开发一套演示、演示和教材，利用水的非凡特性来激发体验式科学学习。这些材料将与康奈尔材料科学中心（见信）、费城富兰克林研究所和伊萨卡科学中心的外展项目合作开发和展示。这些合作将使人们能够与广泛的社会经济规模和代表性不足的群体进行互动。

ABSTRACTCAREER: Fundamental Studies to Advance the Science and Engineering of Water at Negative Pressures CBET- 0747993 Cornell UniversityIntellectual merit: The objectives of this proposal are to provide knowledge and potential practical use of liquid water into a physical regime that has been only sparsely explored experimentally and nearly entirely unexploited technologically: the mechanically stable and thermodynamically metastable state of liquid water at negative pressures. Liquid water is known to be very strong: plants have been shown to move water during transpiration at pressures down to -10 MPa; in the laboratory, it has been placed at pressures -102 MPa. Nonetheless, no human technology has ever exploited water at significant negative pressures (i.e., -1.5 MPa). The negative pressure regime also harbors important information about the outstanding mysteries of water's properties throughout the liquid state: molecular models indicate that the thermodynamic and dynamic anomalies not only persist in this regime but also become more dramatic and tightly coupled to the unusual molecular properties of the fluid. Despite significant interest from the scientific community, the thermodynamic, dynamic, and structural properties of water at negative pressures have been virtually uncharted by experiment. This experimental effort is ripe for undertaking due to the emergence of advanced fabrication tools and recent developments in our laboratory of a new method to drive liquid water deep into the negative pressure regime based on thermodynamic coupling of liquid water to a sub-saturated vapor through molecular membranes. The investigator will exploit these tools to build a microfluidic platform with which to manipulate and study water under tension with unprecedented precision. Their studies will map thermodynamic, dynamic, and structural properties of the stretched state of water with an emphasis on elucidating the molecular origins of macroscopic properties. These measurements will allow them to address some of the deepest outstanding questions about the nature of the liquid water and to fill a major gap in the foundation of knowledge for the science and engineering of this unusual state of matter. This effort is also timely, as it will create a dynamic interface with the rapidly progressing developments in computational modeling of water (see letters of collaboration). Broader Impact: This research has the potential to open a new regime of operation for water management technologies: heat pipes, soil wicks environmental remediation, microfluidic lab-on-a-chip systems for separations and purifications, and breathing electrodes for low temperature fuel cells. In all of these technologies, wicks or membranes have been used mediate the flow of water at positive or very slightly negative pressures (-0.1 MPa), and function is severely limited by the inability to control water under substantial tension. Based on the developments proposed here, these rates of mass transfer could be increased by orders of magnitude and ranges of operational parameters (size, temperature, relative humidity) could be dramatically broadened. Exciting changes in the applications of today's engineers create an obligation to update the curriculum and the modes by which it is taught. The investigator describes plans to modify existing components of the curriculum and add new ones at both the undergraduate and graduate levels. Plans are proposed that address critical challenges in modern engineering curricula: 1) the maintenance of effective teaching of fundamental concepts while updating the context to include more material relevant to new contexts such as microchemical technology and bioengineering, 2) the encouragement of innovative use of skills, such that future engineers are poised to invent as well as operate the next generation of technology, and 3) the encouragement of research as a vital component of both undergraduate and graduate education and as a career option. As new technologies emerge, it is also important to educate the public, and, in particular, children on both the timeless (e.g., thermodynamics) and the timely (e.g., micro and nanotechnology) aspects of their function. In Section VII, I propose the development of a set of presentations, demonstrations, and teaching materials that exploit the extraordinary properties of water to motivate experiential science learning. These materials will be developed and presented in collaboration with the outreach program of the Cornell Center for Material Science (see letter), the Franklin Institute of Philadelphia, and the Ithaca Sciencenter. These collaborations will enable interaction with people from a broad range of socio economic scales and underrepresented groups.