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

ABSTRACTCAREER：基础研究，以促进科学和工程的水在负压CBET- 0747993 康奈尔大学智力优势：本提案的目的是提供知识和潜在的实际使用的液态水到物理制度，只有很少探索实验和几乎完全未开发的技术：在负压下的液态水的机械稳定和热稳定的亚稳态。众所周知，液态水是非常强大的：植物已经被证明在压力低至-10 MPa的蒸腾过程中移动水;在实验室中，它被置于压力-102 MPa。尽管如此，人类技术从未在显著的负压下开采过水（即， -1.5MPa）。负压状态也包含了关于水在整个液态中的性质的重要信息：分子模型表明，热力学和动力学异常不仅在这个状态下持续存在，而且变得更加引人注目，并与流体的不寻常分子性质紧密耦合。尽管科学界对水在负压下的热力学、动力学和结构性质有着极大的兴趣，但实验几乎从未发现过。由于先进的制造工具的出现和最近在我们实验室的一种新方法的发展，以推动液态水深入到负压区的基础上，通过分子膜的热力学耦合的液态水的亚饱和蒸汽，这项实验工作是成熟的。研究人员将利用这些工具建立一个微流体平台，利用它以前所未有的精度操纵和研究张力下的水。他们的研究将绘制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的重大空白。这项工作也是及时的，因为它将创建一个动态的接口与水的计算建模的快速发展（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，土壤灯芯环境修复，用于分离和纯化的微流体芯片实验室系统，以及用于低温燃料电池的呼吸电极。在所有这些技术中，芯或膜已被用于在正压或非常轻微的负压（~ 0.1MPa）下调节水的流动，并且功能由于不能在相当大的张力下控制水而受到严重限制。基于这里提出的发展，这些传质速率可以增加数量级和操作参数（尺寸，温度，相对湿度）的范围可以显着拓宽。令人兴奋的变化，在今天的工程师的应用程序创建一个义务，以更新的课程和模式，它是教。调查员介绍了计划修改现有的课程组成部分，并增加新的本科和研究生水平。提出了解决现代工程课程面临的关键挑战的计划：1）保持基本概念的有效教学，同时更新背景，以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，使未来的工程师准备发明和操作下一代技术，以及3）鼓励研究作为本科和研究生教育的重要组成部分，并作为一种职业选择。随着新技术的出现，同样重要的是要教育公众，特别是儿童，让他们了解永恒的（例如，热力学）和适时（例如，微和纳米技术）方面的功能。在第七节中，我建议开发一套利用水的非凡特性来激励体验式科学学习的演示、演示和教材。这些材料将与康奈尔大学材料科学中心（见信）、费城富兰克林研究所和伊萨卡科学中心的外展计划合作开发和展示。这些合作将使人们能够与来自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.